Abstract: Previously force measurements have been made on a centrifugal pump impeller. The test section inlet of these tests was modified by increasing the volume of the annular region surrounding the shroud. Force measurements were subsequently made on this modified configuration. In addition, a two dimensional model of the impeller was tested. The references provide a description of the facility prior to the current modifications. Briefly, the dynamometer, composed of two parallel plates connected by four strain gaged posts, is mounted between the impeller and the drive shaft. It measures the six components of a generalized hydrodynamic force vector {F} acting on the impeller. The impeller is made to whirl in an orbit eccentric to the volute center, in addition to the normal shaft rotation. Since the eccentric motion is in the lateral plane, perpendicular to the impeller centerline, only the two components of the force vector {F} in this lateral plane will be discussed. Referring to Fig. 1, these forces, in the stationary volute frame of reference, can be represented by [equation included in scanned report's introduction, p. 4](1). The lateral forces, represented by F_x and F_y, can be considered as the sum of two forces: a fixed force, represented by F_(ox) and F_(oy), which the impeller would experience if located at the volute center, and an unsteady force due to the eccentric motion of the impeller, represented by a force matrix [A]. The gravitational and buoyancy forces on the rotor are subtracted out. Dimensionless quantities are used throughout (see Nomenclature for definitions). The data presented in this paper are derived from measurements with the impeller whirling in the circular orbit. When there is no whirl the matrix [A] and vector {F_o} can still be extracted from measurements taken at four fixed eccentric positions, 90 degrees apart, except that these results are limited to the zero whirl value. In general, the force matrix [A] is a strong function of the whirl speed ratio Ω/ω.

ID: CaltechAUTHORS:20180720-171639149

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Abstract: The references [1-4] provide a complete description of the facility. Briefly, the dynamometer, composed of two parallel plates connected by four strain gaged posts, is mounted between the impeller and the drive shaft. It measures the six components of a generalized hydrodynamic force vector {F} acting on the impeller. The impeller can be subject to whirling motion in an orbit eccentric to the volute center, in addition to the normal impeller rotation. Since the eccentric motion is in the lateral plane, perpendicular to the impeller centerline, only the two components of force vector {F} in this lateral will be discussed.

ID: CaltechAUTHORS:FRAHydroLabRptE249-2

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Abstract: Experimental results concerning force coefficients and cavity detachment points under various cavitating conditions on two geometrically similar bi-convex hydrofoils are presented. A linearized cavity flow theory with cavitation separation points determined from the assumption of smooth separation at the detachment point is presented and a comparison is made of these theoretical results with the experiments. Scaling problems with cavitation separation from smooth slender bodies are discussed. With the help of photographic studies three different types of cavitation separation from smooth bodies are proposed.

ID: CaltechAUTHORS:20141014-132257280

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Abstract: Liquid filled hydraulic systems often operate in such a way that cavitation may take place in one or more of the components of the system. Most often the cavitation will take place in a pump or a turbine as the liquid velocity there is usually greatest in these devices. However, cavitation can also occur in bends or elbows or constrictions in the system, such as a venturi tube. When cavitation does take place, the region occupied by the cavitation process displaces liquid that was formerly there, creating in a sense a "reservoir", the volume of which depends upon the extent of the cavitation. In every case the amount of cavitation in any type of hydraulic device will increase as the system pressure is lowered. The liquid that has been displaced causes changes in the motion of the fluid throughout the system causing or requiring time-varying pressure gradients to occur. In most practical hydraulic systems in which cavitation can occur, these transient pressure changes die away and the liquid flow system operates about some steady mean value. Indeed, for some applications cavitation is deliberately introduced into the system in such a way as to cause the flowing system to operate at a steady, stable condition.

ID: CaltechAUTHORS:20141014-162616524

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Abstract: Experiments were made on a ring wing having a chord-diameter ratio of one-half with a profile section consisting of a 10 percent Clark Y airfoil. Measurements were made of the force characteristics of this ring wing in fully wetted flow for several Reynolds numbers and angles of attack; in fully wetted flow these observations agreed with similar previous results on fully wetted ring wings. A portion of the circumference of the ring was also ventilated by the controlled injection of air to provide a cross-force. The magnitude of this cross-force varies with extent of ventilation and with the rate of injection of air. With less than approximately 11 percent of the trailing edge of the wing so ventilated, the cross-force corresponds to the wing in fully wetted flow having an angle of attack of nearly three degrees. Experiments were also made on the rapidity with which this cross-force could be built up at the start of injection or terminated after the ventilation had been established. The termination of the cross-force is very quick and amounts to a time approximately required for the flow to travel a distance of a few wing chords. The build-up process on the other hand is considerably slower, and it appears to be a dynamic one but the scaling laws for this phenomenon are not yet established.

ID: CaltechAUTHORS:20150603-114116510

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Abstract: Theory is developed to estimate the effect of free surface proximity on the initial added mass of a sphere accelerated vertically upward from rest in an ideal fluid. It is assumed that the acceleration regime is sufficiently brief that inertial forces predominate and gravitational effects may be neglected. Results of tests in water indicate that while there are slight viscous and gravitational effects over the acceleration regime, the agreement between theory and experiment is good. It is concluded that over briefer acceleration regimes these effects would decrease and the agreement would improve.

ID: CaltechAUTHORS:20150603-093212131

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Abstract: Cavitation inception measurements were made on the I.T.T.C. Standard Head Form over a range of speeds and dissolved air content. The results were similar to those observed in other water tunnels with resorbers. Cavitation inception indices were observed as low as 0. 4 as compared with the minimum calculated pressure coefficient of O.6. As in previous measurements a pronounced velocity scale effect was observed.

ID: CaltechAUTHORS:20150604-164453478

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Abstract: Viscoelastic fluids show many remarkable phenomena, the best known of which is probably the Weissenberg effect. Because such fluids produce normal stresses in a plane perpendicular to that in which shear takes place, they will climb up a rotating shaft (for example, a stirring rod) immersed in the liquid. A more direct illustration of the elastic properties of the fluid is provided when a rotating flow comes to rest; tracer particles within the flow indicate that the fluid first stops and then flows in the opposite direction for a short duration. An apparently unreported but equally spectacular effect with this type of fluid is the open channel siphon. The sequence of pictures in Fig. 1 illustrates the phenomenon; the upper 4 l. beaker was originally filled with a viscoelastic fluid, and it was then tipped slightly to start the liquid flowing over the lip of the beaker. Once established, the stream continued. The flow rate initially increased, then slackened off and finally stopped when the distance up the beaker wall became too great.

ID: CaltechAUTHORS:20150511-110656605

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Abstract: In the study of long gravity waves of finite amplitude, the main body of the existing theories has been built upon the simplifying assumption that the viscosity is either totally negligible, or adequately described by an empirical law. To date very little systematic account of the viscosity effect has appeared that is based on the Navier-Stokes' equations of motion. Thus, in the important problems of flood waves in rivers, Chezy's formula and a variety of empirical laws of hydraulics have been used to replace the viscous stress terms, and this is the approach taken in most of the hydraulic studies on open channel flows. Among theoretical contributions along this line, one may mention the book by Stoker (1957), the works of Dressler (1949), and of Lighthill and Whitham (1955, I). Dressler developed a rigorous theory of roll waves. In particular he obtained a discontinuous periodic solution in the case of relatively large amplitudes and a continuous periodic (cnoidal) solution in the case of small amplitudes. General flood movement in long rivers has been masterfully investigated by Lighthill and Whitham (1955, I), as a type of kinematic waves. Their method of predicting the transient motion of large amplitude waves with discontinuities (or shocks) is especially noteworthy.

ID: CaltechAUTHORS:20150603-151548176

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Abstract: An experimental method combined with boundary layer theory is given for evaluating the added mass of a sphere moving along the axis of a circular cylinder filled with water or oil. The real fluid effects are separated from ideal fluid effects. The experimental method consists essentially of a magnetic steel sphere propelled from rest by an electromagnetic coil in which the current is accurately controlled so that it only supplies force for a short time interval which is within the laminar flow regime of the fluid. The motion of the sphere as a function of time is recorded on single frame photographs using a short-arc multiple flash lamp with accurately controlled time intervals between flashes. A concept of the effect of boundary layer displacement on the fluid flow around a sphere is introduced to evaluate the real fluid effects on the added mass. Surprisingly accurate agreement between experiment and theory is achieved.

ID: CaltechAUTHORS:20150603-152348259

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Abstract: Experimental results are presented for the effect of a hinge gap on the fully cavitating performance of a flat plate hydrofoil without and with a flap. From the results of the tests it is concluded that for the zero flap deflection, no significant effects of the gap are apparent for the range of the parameters investigated. However, for a 20% flap-to-chord ratio and a 20° flap deflection a significant drop occurs in the lift and moment coefficients for a given gap ratio. This effect increases with increase in gap width. The drag on the other hand is unaffected for the range of values tested. Certain qualitative effects of the jet, arising from the gap, on the cavity appearance are discussed. Comparison of the experimental results for zero gap, with established non-linear theories, show very good agreement.

ID: CaltechAUTHORS:20150603-101938906

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Abstract: This report concludes the work carried out in the general field of hydrodynamics of turbomachines under Contract Nonr 220(24). The objective of the present report is to indicate the scope of the work carried out, to outline in brief the reports and publications issued, and to review current work in progress that has not yet been reported.

ID: CaltechAUTHORS:20150603-150220933

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Abstract: New experimental observations are presented which support the high speed jet mechanism of cavitation damage. A general discussion of the basic hydrodynamic theory involved is given and the importance of certain parameters on damage are pointed out. New techniques for studying the collapse of single cavities are described and the concept and development of a high speed photographic system using a ruby laser is outlined. Magnifications of up to fifty times at picture repetition rates as high as 1,600,000 per second and exposure times of 20 billionths of a second have been achieved.

ID: CaltechAUTHORS:20150527-141909361

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Abstract: Force measurements and visual observations were made in a water tunnel on fully wetted and ventilated flows past a family of conical ring wings having a flat plate section geometry. The diameter-chord ratio was varied from one to three, and the total included cone angle was 12 degrees. The fully wetted flows all exhibited separation from the leading edge except for the largest diameter-chord ratio, a result which was in agreement with previous work. The effect of ventilation is to reduce markedly the lift curve slope. Pressure distribution measurements were also made under ventilating conditions for one member of this series. The effect of ventilation over only a portion of the circumference of the ring was also briefly investigated. Large cross forces were developed by such ventilation and some comparisons are made between this method of obtaining control forces and more conventional methods.

ID: CaltechAUTHORS:ACOhydrolabrptE-138-1

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Abstract: A non-linear theory for the calculation of the flow field of an oblique flat plate under blockage condition is given using the techniques of integral equations. Numerical results are obtained with the aid of a high speed digital computer for the plate situated mid-channel at values of the angle of attack from 50 to 90° and the channel width-chord ratio from 3 to 20. Also obtained are results for the plate situated at two different off-center positions for a channel width-chord ratio 5 and angles of attack less than 30°.

ID: CaltechAUTHORS:AIDhydrolabrpt111-3

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Abstract: The problem of a two-dimensional cavity flow of an ideal fluid with small unsteady disturbances in a gravity free field is considered. By regarding the unsteady motion as a small perturbation of an established steady cavity flow, a fundamental formulation of the problem is presented. It is shown that the unsteady disturbance generates a surface wave propagating downstream along the free cavity boundary, much in the same way as the classical gravity waves in water, only with the centrifugal acceleration owing to the curvature of the streamlines in the basic flow playing the role of an equivalent gravity effect. As a particularly simple example, the surface waves in a hollow potential vortex flow is calculated by using the present theory.

ID: CaltechAUTHORS:HydroLabRpt97-7

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Abstract: When Prof. H. W. Lerbs and Prof. G. Weinblum asked me to prepare a general and broad survey talk on the subject "Propellers and Propulsion" for this International Symposium of Hamburgischen Schiffbau-Versuchsanstalt, I was pleased by having this opportunity to extend my personal congratulations and to participate in this happy event. In view of the fact that this subject has a vast scope containing many special problems which have been under rapid development, I am fully aware of the challenge to prepare a thorough survey, even with the previous excellent review of the state-of-the-art by Prof. Lerbs (1955a, see Reference). Undoubtedly, my effort would be limited by the physical access to the informaiton and literatures not generally available, so I would entitle my talk as "Some recenty developments in propeller theory".

ID: CaltechAUTHORS:HydroLabRpt-E-97-6

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Abstract: A stability analysis is made for the laminar flow of a layer of a viscous and electrically conducting fluid down an inclined plane in a transverse magnetic field. It is found that the effect of the magnetic field, revealed through the Hartmann number, is to stabilize the flow. A simpler and physically clearer approximate treatment of the same problem based on the principle of local balance is also given. The results agree quite satisfactorily with the exact analysis.

ID: CaltechAUTHORS:20140603-144216060

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Abstract: Although delta wings have been known for some time in aeronautics (1)(2) their introduction into a hydrodynamic context has been quite recent. As in the flow of air, the delta wing provides a simple but useful configuration for investigating three-dimensional problems in cavity flows. At the start of the present work (1960), only one theoretical study on this subject was known (3). No information on flow patterns, force characteristics or other properties were available for these shapes. It was accordingly decided to embark on an experimental program with the aim of providing the basic characteristics of the cavitating flow past delta wings, to observe and outline any interesting features of these flows and, finally, to provide a physical basis for any mathematical analysis of the flow that might be undertaken. Measurements of lift, drag and pitching moment and pressure distributions were made on a family of simple flat plate delta shapes of varying apex angle; several configurations outside this family were also tested. These included a diamond plan form, reverse delta, and a delta with a 90 degree bottom. All were without camber and were tested with no yaw angle. After completion of this work, the exhaustive treatment of Reichardt and Sattler (4) appeared which also deals with cavitating delta wings. It is believed, however, that the current report and that of Reichardt are sufficiently different in scope and method to justify the presentation of the present results.

ID: CaltechAUTHORS:KIChydrolabrptE-101-5

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Abstract: The fundamental solution of the gravity waves due to a two-dimensional point singularity submerged in a steady free surface flow of a stratified fluid is investigated. A linearized theory is formulated by using Love's equations. The effect of density stratification p[sub]o(y) and the gravity effect are characterized by two flow parameters [sigma] = -(dp[sub]o/dy)/p[sub]o and [lambda] = gL/U^2, where [lambda]^-1/2 may be regarded as the internal Froude number if L assumes a characteristic value of [sigma]^-1. Two special cases of [sigma] and [lambda] are treated in this paper. In the first case of constant [sigma] (and arbitrary [lambda]) an exact mathematical analysis is carried out. It is shown that the flow is subcritical or supercritical according as [lambda] > or < 1/2, in analogy to the corresponding states of channel flows. In addition to a potential surface wave, which exists only for [lambda]>1/2, there arises an internal wave which is attenuated at large distances for [lambda] > 1/4 and decays exponentially for [lambda] < 1/4. In the second example an asymptotic theory for large [lambda] is developed while [sigma](y) may assume the profile roughly resembling the actual situation in an ocean where a pronounced maximum called a seasonal thermocline occurs. Internal waves are now propagated to the downstream infinity in a manner analogous to the channel propagation of sound in an inhomogeneous medium.

ID: CaltechAUTHORS:HydroLabRpt97-5

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Abstract: Linearized free-streamline theory is used to calculate the spray-sheet thickness and lift-slope for a flat plate, cavitating, two-dimensional hydrofoil in a channel of finite depth with an upper free surface and lower boundary partly free and partly rigid. Only the case of zero cavitation number is considered. Some measurements were made of the submergence of a hydrofoil of four inches chord beneath the undisturbed free surface at velocities of 12 and 18ft./sec. These agree with the trends of the theory but not with the magnitudes, the submergence always being greater than that predicted by the theory.

ID: CaltechAUTHORS:20150604-164105273

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Abstract: The influence of the free surface on the cavitation associated with bodies operating at shallow submergences has long been of interest because of the practical use for such information. The performance of hydrofoil boats is very much dependent on the submergence below the water surface of the hydrofoils, for example. Because of the extreme complexity introduced by the consideration of boundaries of any sort, most theories relating the parameters associated with cavitation are developed for a fluid of "infinite" extent. The task of determining the effects of the boundaries for such a cavitating flow problem then becomes one of experimentation. Such an experiment was performed to determine the free surface effects on a supercavitating, flat plate hydrofoil in two-dimensional flow p:: However, most real flow situations are three dimensional, and the present experiment is a preliminary study to determine the effects of the free surface on the geometry of a ventilated cavity in such a flow. Specifically, the variation of the length of a cavity due to submergence is studied. The cavity is produced by a sharp- edged, circular disk normal to the flow. Figures la and lb show this cavity at two different ventilation numbers. This experiment was planned as a preliminary study to determine the general trend and order of magnitude of the free surface effects, For this reason, the results are presented with the preliminary data reduced to the pertinent dimensionless parameters, uncorrected for tunnel blockage and model scale effects, if any.

ID: CaltechAUTHORS:20150521-164824857

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Abstract: Numerical approximations and a Fortran IV program are given for the calculation by an IBM 7090 computer of the complete and incomplete elliptic integrals of the third kind. In its present form results are limited to six decimal places, but the method is valid for all values of amplitude φ, modulus k and real values of the parameter a^2. For the purpose of completeness, adaptations of other programs for complete and incomplete elliptic integrals of the first and second kind are also presented.

ID: CaltechAUTHORS:20150527-143141902

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Abstract: An experimental program has been carried out for the measurement of the water surface contour due to a submerged hydrofoil of finite span. Because of the hydrofoil downwash, the water surface has a rather pronounced depression in the form of a long, narrow trough which extends many chords aft the hydrofoil. When the trailing vortex cores becomes sufficiently close to the water surface depression, flash ventilation of the vortices and the entire upper surface has been observed to occur abruptly. The model used here was a hydrofoil with a NACA 16-206 section and a rectangular plan form, mounted on a NACA 16-006 strut. The hydrofoil has a chord of 3 inches and an aspect-ratio of l.33. It has been found that the length and depth of the surface depression, and the location of the trough bottom are well defined functions of the Froude number and of the ratio of chord-to-submergence depth. It has also been observed that the distance between the trailing vortex core and the lowest points of the depression is an important parameter in effecting the onset of ventilating flow. This investigation covers a range of flow velocity, angle of attack, depth of submergence, and the flap angle deflection.

ID: CaltechAUTHORS:20150521-165243976

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Abstract: Thomsen in Ref. (1) emphasizes three different states of ventilation occurring at surface-piercing rods, as observed by Hay (2). Hay has towed cylindrical rods which intersect the water surface, at different speeds and at different depths of submergence. From his photographic records, the following observations have been made. At relatively low speeds, an air filled cavity is formed in the wake of the rod, which is open to atmosphere and which extends downwards to a point above the base of the rod. With increasing speed, this point moves downward towards the base of the rod. This form of cavity has been called the "Pre-Base Ventilation State". After the cavity has reached the base, the state was referred to as the "Base Ventilation State", which is found to persist with further increased speed. After the speed was increased over a certain level, the size of the cavity was observed to decrease again forming a cavity closed at the water surface. In this case the state was called the "Post-Base Ventilation State". Since this last phase in the development of the air-cavity has not been observed in the Free Surface Water Tunnel at the California Institute of Technology, it was thought desirable to perform some experiments in order to find the conditions under which this Post-Base Ventilation State can occur. The present results are to be regarded as preliminary. A full explanation of the ventilation phenomena described in the references above and the text of this report to follow is not yet available. Nevertheless, since the results of the present work are at variance with published work, it was thought worthwhile to present them now. Hopefully a more thorough understanding of the ventilation phenomena will be obtained in the not too distant future.

ID: CaltechAUTHORS:20150508-095203295

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Abstract: In this paper the effect of an electromagnetic field on the propagation of a pure torsional elastic wave in a conducting circular cylinder is investigated. The general field equations and boundary conditions are linearized and the equations of motion for an infinitely long circular rod are obtained for the particular electromagnetic field configurations considered. The torsional motion of a solid rod in a steady axial magnetic field with and without a steady electric field is considered. In the first case it is found that a pure torsional mode will not propagate. In the second case a pure torsional mode will propagate and its frequency equation is obtained. The results for a perfect conductor are compared to a real material. The torsional motion of a hollow rod in a steady tangential magnetic field with and without a steady axial electric field is considered. Without the electric field the equations are completely uncoupled and the solution is the standard elastic one. The electric field introduces coupling via the induced magnetic field. The equations of motion are obtained, however the actual solutions are not obtained due to the mathematical complexity involved.

ID: CaltechAUTHORS:20150527-133101786

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Abstract: In this work the author recollects his main experiences and conclusions concerning non-steady cavitation experiments. A simple theory is developed, indicating the appearance of an "apparent curvature", which seems to be helpful in the explanation of the occurrence of certain forms of cavitation. Some photographic examples of non-steady cavity flow are given. Some information is given about specific trouble, experienced with the water tunnel and a possible cure is proposed.

ID: CaltechAUTHORS:20151013-163736146

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Abstract: Recently an exact theory for the cavity flow past an obstacle of arbitrary profile at an arbitrary cavitation number has been developed by adopting a free-streamline wake model. The analysis in this general case leads to a set of two functional equations for which several numerical methods have been devised; some of these methods have already been successfully carried out for several typical cases on a high speed electronic computer. In this paper an approximate numerical scheme, somewhat like an engineering principle, is introduced which greatly shortens the computation of the dual functional equations while still retaining a high degree of accuracy of the numerical result. With such drastic simplification, it becomes feasible to carry out this approximate mrmerical scheme even with a hand computing machine.

ID: CaltechAUTHORS:HydroLabRpt111-1

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Abstract: In Part I of this paper a free-streamline wake model was introduced to treat the fully and partially developed wake flow or cavity flow past an oblique flat plate. This theory is generalized here to investigate the cavity flow past an obstacle of arbitrary profile at an arbitrary cavitation number. Consideration is first given to the cavity flow past a polygonal obstacle whose wetted sides may be concave towards the flow and may also possess some gentle convex corners. The general case of curved walls is then obtained by a limiting process. The analysis in this general case leads to a set of two functional equations for which several methods of solution are developed and discussed. As a few typical examples the analysis is carried out in detail for the specific cases of wedges, two-step wedges, flapped hydrofoils, and inclined circular arc plate. For these cases the present theory is found in good agreement with the experimental results available.

ID: CaltechAUTHORS:HydroLabRpt97-4

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Abstract: A perturbation theory is applied to investigate the small-time behavior of unsteady cavity flows in which the time-dependent part of the flow may be taken as a small-time expansion superimposed on an established steady cavity flow of an ideal fluid. One purpose of this paper is to study the effect of the initial cavity size on the resulting flow due to a given disturbance. Various existing steady cavity-flow models have been employed for this purpose to evaluate the initial reaction of a cavitated body in an unsteady motion. Furthermore, a physical model is proposed here to give a proper representation of the mechanism by which the cavity volume may be changed with time; the initial hydrodynamic force resulting from such change is calculated based on this model.

ID: CaltechAUTHORS:HydroLabRpt97-3

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Abstract: An experimental program was conducted to investigate the characteristics of a fully cavitating two-dimensional flat plate hydrofoil in the presence of a free surface. The submergence of the hydrofoil was varied from the planing condition at the free surface to a depth corresponding to 2.16 model chords. Near the surface the cavities formed by venting to the atmosphere, but at the deeper submergences, they had to be artificially formed by supplying them with air. The normal force, the moment about the leading edge, the center of pressure location, the cavity length, and the volumetric air flow rate into the cavity are presented as functions of angle of attack, cavitation number, Froude number, and proximity to the free surface.

ID: CaltechAUTHORS:DAWhydrolabrptE118-12

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Abstract: This test program is one of a series designed to investigate the properties of base-ventilated hydrofoils. The purpose of this study was to determine the two-dimensional force and ventilation characteristics of an uncambered hydrofoil which could be truncated by removing four removable trailing edge sections. The program was performed at the request of T. G. Lang of the Naval Ordnance Test Station, Pasadena, who in Reference 1 analyzed the possibilities of reducing the cavity drag of base-ventilated hydrofoils by selecting appropriate section profiles and foil base thicknesses. Using a profile developed in Reference 1, it was intended to study the effects of ventilation air flow rate, angle of attack, and the position of the trailing edge cutoff points, and to compare the experimental values of the drag with those predicted from a linearized flow theory.

ID: CaltechAUTHORS:BREhydrolabrptE-108-12

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Abstract: The purpose of this experimental study is to determine the contour of the distorted water surface behind a hydrofoil operating at shallow depths of submergence. The effects of foil depth, Froude Number, and the angle of attack were investigated for a non-cavitating hydrofoil without any flap deflections. The characteristics of the surface depression behind a foil are important when considering the applications of canard or tandem foil systems. A theoretical analysis of the same phenomena is being made by Daniel Ai and a comparison between theory and experiment will be made in the near future.

ID: CaltechAUTHORS:BREhydrolabrptE-110-3M

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Abstract: A complete analysis of acoustic absorption by a spherical gas bubble is developed by the application of the classical Rayleigh method. The absorption considered is that due to the viscosity and heat conduction of the gas bubble. Specific results are presented for the S-wave scatter and absorption for the case of an air bubble in water, and the absorption effects of viscosity and heat conduction alone are calculated explicitly. The results found here are of similar magnitude to those found by Pfriem and Spitzer who used an approximate procedure.

ID: CaltechAUTHORS:HydroLabRpt85-19

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Abstract: [no abstract]

ID: CaltechAUTHORS:20140611-100012389

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Abstract: The propagation of a longitudinal elastic strain pulse in a wide rectangular bar is considered on the basis of approximate plane-stress equations of motion. Asymptotic expressions are obtained which, for large distances of travel, describe the pulse propagation in a semi-infinite strip with stress-free lateral edges, subject to the conditions that a uniform normal stress with a step-function time dependence is applied to the end and that the end is laterally constrained. Particular emphasis is given to describing the warping of plane sections during passage of the strain pulse.

ID: CaltechAUTHORS:20150526-140944534

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Abstract: The plane-stress theory presented in Part I is shown to qualitatively predict the warping of plane sections observed in transient fringe patterns obtained using birefringent coatings and in dynamic photoelastic pictures obtained by other investigators. Measurements using conventional techniques are described in which wide rectangular bars were subjected to a longitudinal step-function pressure loading produced by a shock tube. Comparisons show that the gross features of the experimental records for the head of the pulse are qualitatively predicted by the theory. Both theory and experiment show that short-wavelength second mode disturbances arrive very early. Experimentally it is observed that these disturbances are accompanied by thickness mode activity which cannot be accounted for by the plane-stress theory.

ID: CaltechAUTHORS:20150511-105940240

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Abstract: An investigation in the High Speed Water Tunnel of the hydrodynamic characteristics of a family of three-dimensional sharp-edged hydrofoils is described. Four rectangular planform, 6 degree wedge profiles with aspect ratios of 4.0, 2.0, 1.0 and 0.5 were tested over a range of cavitation numbers from noncavitating to fully cavitating flow. The effects of aspect ratio on the flow and cavity configurations and on the lift, drag and pitching moment are discussed. Where data were available the results have been compared with the two-dimensional case.

ID: CaltechAUTHORS:KERhydrolabrpt47-14

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Abstract: In the first section of this report a review of some of the attempts to measure cavity collapse pressures is presented. The second section deals with the experimental measurement of the stresses developed in a solid subjected to cavitation. Single, hemispherical cavities were created in water at the end of a pressure bar. Both the generation and collapse of such cavities gave rise to transient stress pulses which traveled along the bar and were detected by means of an X-cut quartz crystal. The charge appearing on the opposite faces of the quartz disc was allowed to develop a voltage which was subsequently amplified and :recorded photographically from an oscilloscope. The oscillograms obtained in this manner yielded information regarding both the total lifetime of the cavity and the peak amplitude of the force developed during its collapse. Concurrent with the recording of the stress pulses, high speed photographs covering the total lifetime of the cavity were taken. These photographs furnished information regarding both the maximum diameter attained by the cavity and the time history of collapse of the cavity.

ID: CaltechAUTHORS:20150526-162727993

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Abstract: A perfect fluid theory, which neglects the effect of gravity, and which assumes that the pressure inside a cavitation bubble remains constant during the collapse process, is given for the case of a nonhemispherical, but axially symmetric cavity which collapses in contact with a solid boundary. The theory suggests the possibility that such a cavity may deform to the extent that its wall strikes the solid boundary before minimum cavity volume is reached. High speed motion pictures of cavities generated by spark methods are used to test the theory experimentally. Agreement between theory and experiment is good for the range of experimental cavities considered, and the phenomenon of the cavity wall striking the solid boundary does indeed occur. Studies of damage by cavities of this type on soft aluminum samples reveals that pressures caused by the cavity wall striking the boundary are higher than those resulting from a compression of gases inside the cavity, and are responsible for the damage.

ID: CaltechAUTHORS:20150526-144122096

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Abstract: The phenomenon of resuspension has been considered to be an important factor in the imperfect behavior of sedimentation basins receiving suspensions containing flocculent solids. Resuspension is the entrainment into the flow of particles that have once settled to the floor of the basin. This investigation has been undertaken to study the resuspension phenomenon and to find ways in which its harmful effects can be reduced. Resuspension has been found extremely difficult to isolate and define scientifically because many other factors produce the same overall effect upon the settling tank. Furthermore it is practically necessary to identify individual particles in order to know whether a particular one found in suspension in the downstream portion of a settling tank had earlier been settled out and resting on the floor. Laboratory studies on settling tank behavior were conducted on a glass-walled "scour flume" 1.27 ft wide by 14 ft long with depth adjustable from 0.5 to 2.0 ft (see Fig. 1.1). In order to simulate certain aspects of the behavior of full-scale settling tanks the laboratory flume was fitted with moving flight scrapers similar to those installed in primary sewage settling tanks. For some of the later tests the flume was fitted with 14 probes that made it possible to sample the tank contents at practically any point of five cross sections along the length of the flume. Most of the studies on the laboratory flume utilized a discrete suspension of gilsonite {s. g. 1.04) particles or a flocculent suspension of ferric chloride and bentonite clay particles. Tests for critical velocity required for entrainment of particles from a smooth bed showed that fine light particles are more easily lifted from the bed than was previously supposed. With scrapers moving upstream, the critical velocity for two sizes of gilsonite tested was found to vary between 10.5 and 14.5 times the particle settling velocity. Field and laboratory studies on one scheme proposed to improve the performance of settling tanks - a series of transverse sloping baffles installed throughout the main body of a rectangular settling tank - both indicate that baffling a tank is not the answer. Tests on full-scale settling tanks of a sewage treatment plant showed that conventional measures of settling tank performance are meaningless when the suspension entering the tank is flocculent (as is sewage). Newer measures of performance are proposed, which show promise in evaluating the behavior of settling tanks receiving flocculent suspensions.

ID: CaltechAUTHORS:20140626-140655730

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Abstract: Continued interest in the application of cavitating hydrofoils to various types of lifting and control surfaces on water craft, the recently publicized super-cavitating propeller and other types of rotating machinery, has resulted in a considerable amount of information on the behavior of the cavitating flow past isolated objects. The flow details of many configurations of interest may not, however, be approximated well by information on isolated shapes. For example, the close proximity of the neighboring vanes in a lifting ladder foil used for the support of a hydrofoil boat might conceivably have an important effect on the lift of an individual blade. The same effect may be expected to occur in the flow through the blades of a propeller with extensive cavitation. The problem of the cavitating flow through a cascade or lattice of hydrofoils is then of considerable technical interest, although only a few works have appeared on this subject.

ID: CaltechAUTHORS:ACOhydrolabE79-2

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Abstract: This contract was initiated in October 1950 to continue the basic research programs then in progress at this laboratory in several important areas in hydrodynamics.

ID: CaltechAUTHORS:20150527-132750013

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Abstract: The test section of the High-Speed Water Tunnel (1) was modified in preparation for experiments on the force and cavitation characteristics of torpedo fins and control surfaces mounted on a reflection plane. The modification involved installing a reflection plane in the 14-inch diameter working section of the tunnel. The reflection plane is described and the results of flow calibrations of the tunnel test section with the reflection plane installed are given. This report summarizes the work completed under Task 4 of Contract NOrd-16200.

ID: CaltechAUTHORS:20150526-133033752

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Abstract: Static force and moment coefficients were measured in the High Speed Water Tunnel on nonpowered models of a propeller-stabilized and controlled torpedo. The tests were made on three propeller configurations and four body-fin combinations. Representative tests were conducted over a range of tunnel velocities. Data are presented as functions of body angle of attack and propeller shaft deflection. A comparison is presented of the experimental data and the theoretical analysis of T. Lang of the Naval Ordnance Test Station, Pasadena.

ID: CaltechAUTHORS:20150603-111002034

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Abstract: Report number E -73.3, published by this Laboratory in June 1957, (Ref. 1) presents certain dynamic coefficients for a model of the Basic Finner Missile (Fig. 1) which had been measured on the angular dynamic balance in the High Speed Water Tunnel at this Laboratory. Several of the desired coefficients, specifically Y_r' coefficient of rotary force derivative Y_v' virtual inertia coefficient (lateral acceleration) N_r' coefficient of rotary moment derivative N_v' virtual moment of inertia coefficient (lateral acceleration) remained undetermined at that time. By employing the translational dynamic balance and its associated internal moment balance, it had been hoped that the missing values for these coefficients would be supplied. Only partial success has been achieved, insofar as numerical results are concerned, at contract expiration time. The coefficient of static force derivative, Y_v', and the virtual inertia coefficient, Y_v', have been measured as part of this investigation. These coefficients have been designated Z_w' and Z_ẇ' in this report to comply with the new direction of model motion with respect to the tunnel coordinate system. Since the first of these, Z_w', had already been determined in the angular dynamic measurements, only the presentation of a value for Z_ẇ' is new. This coefficient had appeared in linear combination with the coefficient of rotary force derivative; hence the latter important quantity also is now uniquely determined. In addition to the force reactions, the moments arising from transverse velocity and acceleration components were also measured, but under conditions of undetermined deflection of the model-spindle assembly. For this reason the moment coefficients have not been presented here, nor have the experimental procedures used to obtain them been included. Instead, a detailed discussion of both the apparatus and the experimental procedures has been planned for reference 3.

ID: CaltechAUTHORS:20150603-104731801

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Abstract: In recent years a number of papers treating linearized free streamline problems have appeared subsequent to Tulin's introductory paper on this subject (1).* Among these may be mentioned Wu's extension of Tulin's method for supercavitating hydrofoils with arbitrary shape and cavitation number (2), hydrofoils with cavitation only near the leading edge (3), supercavitating hydrofoils in cascade (4) and Cohen's work on wall interference effects (5). In all of the above works the hydrfoil is assumed to be in a force-free field. However, Parkin recently has estimated the effect of a gravity field normal to the direction of the flow by means of a simplified representation of the gravity effect on the cavity boundary condition (6). As yet the problem of the longitudinal gravity field does not seem to have been discussed. Fully cavitated flows are known to occur in axial gravitational fields. The cavity associated with vertical water entry or exit is one example. An effect similar to that of axial gravity occurs when fully cavitating flow takes place in a large water tunnel with slightly diverging walls. The longitudinal pressure gradient that results from the variable cross section plays a role much like that of a force field. It appears then, that to have an understanding of free streamline problems in all cases of possible technical interest, the effect of an axial or longitudinal gravitational field must be examined.

ID: CaltechAUTHORS:ACOhydrolabE79-1

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Abstract: The shape of the cavity formed in ;·rater by a circular disk at an angle of attack is derived. The empirical evaluation is based on experimental data obtained with air cavities in the Free Surface Water Tunnel. The effects of model size, free stream velocity and cavitation number on cavity shape are presented. The profile shape of the cavity is assumed to be composed of two superposable phenomena: (1) the cavity shape without gravity effects (2) the displacement of the cavity due to gravity An empirical relation is obtained for the buoyant displacement of the cavity centerline. A quasi-elliptical equation is derived which accurately describes the shape of the cavity about its centerline for the disk at zero angle of attack. The equation is modified and applied to the profile shape of a cavity formed by a circular disk at angles of attack up to 30 degrees. All experimental data are presented in both graphic and analytic form.

ID: CaltechAUTHORS:20150603-103047421

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Abstract: Experimental force measurements on several truncated cone-cylinder bodies operating in full cavity flow are reported. Lift, drag and pitching moment coefficients and the center of pressure are presented as functions of angle of attack for cavitation numbers from 0.02 to 0.06. The lift and drag coefficients are compared with predicted results which are based on the summation of the forces on individual body components. Discrepancies between the experimental and the predicted results are discussed.

ID: CaltechAUTHORS:20150526-134626740

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Abstract: A series of tests were performed in the High Speed and Free Surface Water Tunnels to measure the forces and moments on planing circular cylinders. Lift, drag, moment, and center of pressure are presented for cylinders planing on flat and laterally-curved surfaces. The ratio of the cylinder diameter to the planing surface diameter was varied from 0 to 0.538. The effects of cavitation on the forces and moments were investigated by varying the local planing body cavitation number from 0.003 to 3.3. The results of these tests show that the cavitation number cf the planing body is an important modeling parameter for cylinders. Both solid and open-ended, vented cylinders were tested.

ID: CaltechAUTHORS:20150526-134108562

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Abstract: The results of static force tests on a 2-in. diameter model of Weapon "A" in the High Speed Water Tunnel are presented. Drag coefficient was measured for Reynolds numbers from l.3 to 8.0 x 10^6 at zero degrees attack angle. Lift, drag, and pitching moment were measured as a function of attack angle for Reynolds numbers of 3.8 and 5.1 x 10^6.

ID: CaltechAUTHORS:20150526-132752341

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Abstract: The results of force tests of models of the Basic Finner missile configuration in fully wetted flow in the High Speed Water Tunnel are presented. The static lift, pitching moment and drag were measured for angles of attack up to 14 degrees and for Reynolds numbers from 0.7 to 8.5 x 10^6. The results of these tests performed on the static force balance are in good agreement with coefficients determined from free flight drag studies in the Controlled Atmosphere Launching Tank and at the U. S. Naval Ordnance Test Station, Pasadena.

ID: CaltechAUTHORS:20150526-132445332

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Abstract: The results of drag measurements on a flat lamina, wedges, a circular cylinder and a scoop channel in two- dimensional cavitating flow in the High Speed Water Tunnel are presented. Cavity geometry data are also included. The results are compared with available theoretical drag coefficients and cavity dimensions.

No.: E-73.6
ID: CaltechAUTHORS:20161114-120725296

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Abstract: Equipment developed in this Laboratory permits the determination of eight of the dynamic coefficients useful in describing the force and moment reactions on a submerged body moving in water. These coefficients comprise the partial derivatives of moment (about the yaw axis) and of force (in the horizontal plane, and perpendicular to the longitudinal axis) with respect to velocity and acceleration components in specified directions. So long as the instantaneous angles of attack are small and scale effects are absent, these coefficients have constant values. A complete list of coefficients is given in Ref. (1), as are definitions, sign conventions and formulas for making the coefficients nondimensional. The eight coefficients tabulated below are those pertinent to lateral translation and rotation about the yaw axis for a body of revolution: Nr' coefficient of rotary moment derivative Nr[dot]' virtual moment of inertia coefficient (angular acceleration) Nv' coefficient of static moment derivative Nv[dot]' virtual moment of inertia coefficient (lateral acceleration) Yr' coefficient of rotary force derivative Yr[dot]' virtual inertia coefficient (angular acceleration) Yv' coefficient of static force derivative Yv[dot]' virtual inertia coefficient (lateral acceleration) where the prime indicates that the coefficients are in dimensionless form. It is the purpose of the experimental program undertaken at this Laboratory to determine the numerical values of the above quantities for the Basic Finner missile (Fig. 1). Because of the required differences in the experimental methods, however, the program was divided into two parts. This report deals only with Part 1, and is restricted to the following quantities: Nr[dot]', Nv', Yr[dot]', Yv', and the linear combinations Nr' - Nv[dot]' and Yr' - Yv[dot]'. Remaining quantities will be the subject of another report.

ID: CaltechAUTHORS:KIChydrolabrptE-73-3

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Abstract: This final report covers a period of approximately four years, since this contract was initiated in March 1952. Furthermore, even at that time, some of the phases of the work had already been started. In discussing the progress of these different phases, no attempt will be made to separate these initial phases from the continuation under this contract. The most important results obtained during the life of this contract have already been published in a series of technical articles.(1, 2, 3) Therefore, in such cases only summaries will be incorporated herein. In cases in which the phases have not reached the publication stage, a more complete outline will be found, Four phases of this investigation of cavitation will be reported, as follows: I. Effect of Pressurization on Cavitation Properties of Water II. Mechanics of Fixed Cavitation III. Hydromechanics of Cavitation Damage IV. Preliminary field tests of Intensity of Cavitation Phase I has not been reported in the literature; II, III, and IV have been presented in the references cited.

ID: CaltechAUTHORS:20140603-142729681

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Abstract: The wave profile generated by an obstacle moving at constant veiocity U over a water surface of infinite extent appears to be stationary with respect to the moving body provided, of course, the motion has been maintained for a long time. When the gravitational and capillary effects are both taken into account, the surface waves so generated may possess a minimum phase velocity c[sub]m characterized by a certain wave length, say [lambda][sub]m (see Ref. 1, p. 459). If the velocity U of the solid body is greater than c[sub]m, then the physically correct solution of this two-dimensional problem requires that the gravity waves (of wave length greater than [lambda][sub]m) should exist only on the downstream side and the capillary waves (of wave length less than [lambda][sub]m) only on the upstream side. If one follows strictly the so-called steady-state formulation so that the time does not appear in the problem, one finds in general that it is not possible to characterize uniquely the mathematical solution with the desired physical properties by imposing only the boundedness conditions at infinity. [Footnote: In the case of a three-dimensional steady-state problem, even the condition that the disturbance should vanish at infinity is not sufficient to characterize the unique solution.] Some stronger radiation conditions are actually necessary. In the linearized treatment of this stationary problem, several methods have been employed, most of which are aimed at obtaining the correct solution by introducing some artificial device, either of a mathematical or physical nature. One of these methods widely used was due to Rayleigh, and was further discussed by Lamb. In the analysis of this problem Rayleigh introduced a "small dissipative force", proportional to the velocity relative to the moving stream. This "law" of friction does not originate from viscosity and is hence physically fictitious, for in the final result this dissipation factor is made to vanish eventually. In the present investigation, Rayleigh's friction coefficient is shown to correspond roughly to a time convergence factor for obtaining the steady-state solution from an initial value problem. (It is not a space-limit factor for fixing the boundary conditions at space infinity, as has usually been assumed in explanation of its effect). Thus, the introduction of Rayleigh's coefficient is only a mathematical device to render the steady-state solution mathematically determinate and physically acceptable. For a physical understanding, however, it is confusing and even misleading; for example, in an unsteady flow case it leads to an incomplete solution, as has been shown by Green. Another approach, purely of a physical nature, was used by Michell in his treatment of the velocity potential for thin ships. To make the problem determinate, he chose the solution which represents the gravity waves propagating only downstream and discarded the part corresponding to the waves traveling upstream. For two-dimensional problems with the capillary effect, this method would mean a superposition of simple waves so as to make the solution physically correct. Some other methods appear to be limited in the necessity of interpreting the principal value of a certain kind of improper integral. In short, as to their physical soundness and mathematical rigor, or even to their merits or demerits, the preference of one method over the others has remained nevertheless a matter of considerable dispute. Only until recently the steady-state problem has been treated by first formulating a corresponding initial value problem. A brief historical sketch of these methods is given in the next section. The purpose of this paper is to try to understand the physical mechanism underlying the steady configuration of the surface wave phenomena and to clarify to a certain extent the background of the artifices adopted for solution of steady-state problems. The point of view to be presented here is that this problem should be formulated first as an initial value problem (for example, the body starts to move with constant velocity at a certain time instant), and then the stationary state is sought by passing to the limit as the time tends to infinity. If at any finite time instant the boundary condition that the disturbance vanishes at infinity (because of the finite wave velocity) is imposed, then the limiting solution as the time tends to infinity is determinate and bears automatically the desired physical properties. Also, from the integral representation of the linearized solution, the asymptotic behavior of the wave form for large time is derived in detail, showing the distribution of the wave trains in space. This asymptotic solution exhibits an interesting picture which reveals how the dispersion* generates two monochromatic wave trains, with the capillary wave in front of, and the gravity wave behind, the surface pressure. *[Footnote: By dispersive medium is meant one in which the wave velocity of a propagating wave depends on the wave length, so that a number of wave trains of different wave lengths tends to form groups, propagating with group velocities which are in general different from the phase velocities of individual wave trains. In case of waves on the water surface, both the gravity and surface tension are responsible for dispersion.] The special cases U< c[sub]m and U = c[sub]m are also discussed. The viscous effect and the effect of superposition are commented upon later. Through this detailed investigation it is found that the dispersive effect, not the viscous effect plays the significant role in producing the final stationary wave configuration.

ID: CaltechAUTHORS:HydroLabRpt21-23

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Abstract: The forces and moments which act on a submerged body undergoing unsteady motion can be described in terms of selected dimensionless constant hydrodynamic coefficients if the instantaneous angles of attack are kept small. To determine the values of these coefficients a model of the body can be supported from the spindle of a dynamic balance (1) in the flowing stream of a water tunnel working section. This procedure was carried out for certain coefficients on a 2-inch diameter model of the Mk-13 torpedo (Fig. 1) using the Angular Dynamic Balance in conjunction with the High Speed Water Tunnel at the California Institute of Technology, Hydrodynamics Laboratory.

ID: CaltechAUTHORS:20150506-152403692

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Abstract: An experimental investigation of the two-dimensional hydrodynamic characteristics of a thin, supercavitating hydrofoil is described. The effects of twist and vibration of the thin hydrofoil model are considered, and experimental techniques for investigating spanwise twist and leading edge vibration and data correction methods are described. The theory of Wu for the forces on fully cavitating hydrofoils was used to calculate the forces on this profile. The calculated lift is in good agreement with the experimental results; however, the measured drag differs appreciably from the theoretical values.

ID: CaltechAUTHORS:WAIhydrolabrpt47-8

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Abstract: Part 1 of an experimental and analytical investigation of the behavior in free flight of inertia-propelled bodies that are fin-stabilized is presented. The dynamic response in vertical trajectories starting from rest has been found for two sizes of a single configuration of the Basic Finner Research Missile with a variety of model parameters and initial conditions. A relatively simple formulation of the drag function for longitudinally accelerated motion in the laminar flow regime is found to give excellent agreement between predicted and experimental behavior. Time-position histories of test trajectories are presented in tabular form.

ID: CaltechAUTHORS:20150526-133726751

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Abstract: The paper reviews briefly experimental techniques and data-correction procedures developed in connection with studies in the High Speed Water Tunnel, California Institute of Technology, for hydrofoil force measurements. The matters discussed relate chiefly to problems of force measurement in cavitating flow and to procedures devised to solve them. Items considered in this connection are water-tunnel balances, the effects of tip-clearance flows, tare corrections, the importance of cavity-pressure measurements, cavitation scaling, tunnel-wall effects, and hydroelastic effects.

ID: CaltechAUTHORS:PARhydrolabrpt47-10

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Abstract: The measurement of dynamic coefficients in a water tunnel is considered generally, and it is shown that the forces depend only on relative velocity provided the flow in the water tunnel is steady. A method of measuring the coefficient N_r, relating cross force to yawing angular velocity utilizing an internal balance, is described. Experimental results are compared with theory, showing good agreement in the case of the coefficient N_r.

ID: CaltechAUTHORS:20150526-140425271

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Abstract: The lifting problem of fully cavitated hydrofoils has recently received some attention. The nonlinear problem of two-dimensional fully cavitated hydrofoils has been treated by the author, using a generalized free streamline theory. The hydrofoils investigated in Ref. 1 were those with sharp leading and trailing edges which are assumed to be the separation points of the cavity streamlines. Except for this limitation, the nonlinear theory is applicable to hydrofoils of arbitrary geometric profile, operating at any cavitation number, and for almost all angles of attack as long as the cavity wake is fully developed. By using an elegant linear theory, Tulin has treated the problem of a fully cavitated flat plate set at a small angle of attack and operated at arbitrary cavitation number. In the case of hydrofoils of arbitrary profile operating at zero cavitation number, some interesting simple relationships are given by Tulin for the connection between the lift, drag and moment of a supercavitating hydrofoil and the lift, moment and the third moment of an equivalent airfoil (unstalled). In the present investigation, Tulin's linear theory is first extended to calculate the hydrodynamic lift and drag on a fully cavitated hydrofoil of arbitrary camber at arbitrary cavitation number. A numerical example is given for a circular hydrofoil subtending an arc angle of 160, for which the corresponding nonlinear solution is available. A direct comparison between these two theories is made explicitly for the flat plate and the circular arc hydrofoil. Some important aspects of the results are discussed subsequently.

ID: CaltechAUTHORS:HydroLabRpt21-22

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Abstract: This report concludes the work conducted by the Hydrodynamics Laboratory at the California Institute of Technology under Contract N6onr-44, Task II, in the general field of hydraulic machinery. This work was initiated in January 1947 under the initial guidance of Professors Knapp and Hollander. It has subsequently been continued by additional amendments to the original contract up to the present. The over-all objectives of this program were to make detailed observations and measurements of the internal flow in rotating impellers and stationary diffusors to permit the establishment of accurate design procedures for hydraulic machinery, and to serve as a starting point for realistic mathematical analysis of such flows. It is the intention of this report to indicate the scope of the work done under this contract and to describe the facilities built for its experimental end. A further aim is to outline, in brief, the reports and publications issued and some incidental benefits derived from this project.

ID: CaltechAUTHORS:ACOhydrolabE19-11

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Abstract: An experimental study of the dynamic control and stability of submarines has been made by means of small-scale, free-running, powered and controlled models at the California Institute of Technology, Hydrodynamics Laboratory. The experimental and theoretical basis of the modeling of the behavior of fully submerged submarines is discussed. The design and construction of the models are described, and development of experimental techniques is outlined. The experimental program was conducted with models of two full-scale submarines -- the U.S.S. Odax and the U.S.S. Albacore -- to (1) evaluate the efficacy of small-scale modeling, and (2) to predict control characteristics of a boat of radically new design. Satisfactory agreement between the dynamic behavior in free flight of the small-scale (120:1) model and the Guppy-type submarine Odax is demonstrated for one type of maneuver. Zig-zag maneuvers in the vertical plane were chosen for this purpose because of their simplicity and suitability for comparison with available full-scale data. The model's diving planes were made to reproduce the time-sequence of the diving plane motions of the full-scale submarine and the resulting depth and inclination responses compared to those of the full size vessel. The consistency of the model's behavior was evaluated from repeated tests with each of four selected control programs for which only a single full-scale test was run. Predictions of the dynamic control and maneuverability characteristics of the U.S.S. Albacore (AGSS 569) Scheme IV submarine, which marks a radical departure in hull design, were made with a 100 to 1 scale model. This model was built at about the same time that the keel was laid for the prototype ship. The studies made with this model were divided into three parts: (1) Control characteristics in the vertical plane. (2) Turning characteristics with rudder control alone. (3) Turning characteristics with depth control, and with combination depth-and-roll control. The tests under item (1) were made with two sets of appendages (tail structure, bow planes, and bridge fairwater), for which only minor differences in control response were found and no measurable difference noted in directional stability. Items (Z) and (3) were made with one set of appendages (corresponding to those first used on the prototype) and with Froude-scaled model velocity. Specific maneuvering problems, such as the determination of control plane programs required to execute optimum dives or horizontal turns without changing depth, are solved by successive approximation with the model. The tests show that a high degree of prescience is required and that precise execution of the control program is necessary to successfully accomplish an optimum maneuver. Comparison of the behavior of the two models shows that the Albacore has a greater degree of directional stability and a faster response to its controls than the Odax. This is certainly due to its better hydrodynamic design. The Albacore model also demonstrated much better consistency in it- own behavior than did the Odax model. This is due in part to better design and in part to the improvements made in the techniques of building and operating the models and in processing the model test data. At the time of this writing, no detailed comparisons have been made between results obtained with the Albacore model and those of the sea trials of the prototype which were made in the fall of 1955. The few spot comparisons which were made (but not included in this report) show good agreement. Detailed comparisons of these two sets of tests will be made at the David Taylor Model Basin (under whose supervision the sea trials were conducted) and will be the subject of a separate report.

No.: E-27.2
ID: CaltechAUTHORS:20190617-163817071

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Abstract: A design procedure for axial-flow pump impellers is presented that accounts for induced interference effects in the prediction of performance. Induced interference velocities at an impeller blade have been calculated using a three-dimensional model that includes the effects of the other blades and of the total downstream vorticity along the center line of the pump. The design method considers improvement of cavitation conditions by specifying the radial variation of the design parameters such that the pressure distributions on all radial sections are similar. An analysis of optimizing the impeller geometric parameters for cavitation conditions is presented to permit the initial choices of the quantities appearing in the design procedure. Experimental work on a two-bladed impeller has yielded results that give good support to all aspects of the design method.

ID: CaltechAUTHORS:20150527-134530908

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Abstract: An investigation in the High Speed Water Tunnel of the two-dimensional hydrodynamic characteristics of sharp-edged hydrofoils is described. The lift, drag, and pitching moment were measured in cavitating and noncavitating flows for flat plate and circular arc profiles. The theory of Wu for the forces on sharp-edged profiles in full cavity flow and the experimental results showed good agreement over a wide range of attack angles.

ID: CaltechAUTHORS:HydroLabRptE-47-6

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Abstract: The results of force and cavitation tests on two hydrofoils in two-dimensional flow are presented. The hydrofoils are the NACA 4412 profile and a modified circular arc, flat plate, hydrofoil designated as a Walchner profile 7. The results of experiments performed in wind tunnels and in other water tunnels are presented for comparison. The experiments described in this report are the first tests using the High Speed Water Tunnel two-dimensional working section and the new force balance; therefore, the experimental setup, procedure and methods of data reduction have been described in detail. The results of the tests on the NACA 4412 hydrofoil are in good agreement with those obtained for this profile in the Langley two-dimensional low-turbulence wind tunnel. The results of the tests on the circular arc, flat plate hydrofoil are not in good agreement with the results obtained by Walchner for cavitating flow. The differences in the forces on the hydrofoils can be accounted for with a difference in cavitation number of approximately 0.1. The tests indicate that accurate force measurements can be made with the new water tunnel force balance and that the methods developed during these tests provide a satisfactory means of obtaining the section characteristics of hydrofoils in cavitating and noncavitating flow.

ID: CaltechAUTHORS:KERhydrolabrpt47-5

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Abstract: The results of force tests on the NACA 66_(1-012) hydrofoil in noncavitating and cavitating two-dimensional flow are presented. The results of wind tunnel tests on this profile are included for comparison with the results of the noncavitating water tunnel experiments. The noncavitating experiments were made at Reynolds numbers from 0.89 to 1.65 x 10^6 and the cavitation experiments at Reynolds numbers of 0.89 and 1.18 x 10^6.

ID: CaltechAUTHORS:KERhydrolabrpt47-7

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Abstract: A series of cavitation experiments in an axial flow pump are described. It is found that cavitation first occurs in a tip vortex formed by the flow through the tip clearance space of the rotor blade. The effect of tip clearance and several cavitation suppression devices are shown. The schemes tested were rigid end plates attached to the blade ends, strings, and a continuous rotor shroud. Of these, the shroud appears to delay the inception of tip cavitation best for axial flow pumps.

ID: CaltechAUTHORS:20150529-142202908

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Abstract: Recently Tulin and Wu have treated the problem of fully developed cavitation on flat plate and cambered foils. In these treatments, the length of the cavity is always greater than the chord of the hydrofoil and the cavity is assumed to start at the leading edge of the plate. The purpose of this note is to extend Tulin's work to account for partial cavitation, i.e., when the cavitation bubble is less than the hydrofoil chord.

ID: CaltechAUTHORS:ACOhydrolabE19-9

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Abstract: Ultra-high-speed photoelastic techniques have been applied to a study of the transient stresses and strains in a photoelastic plastic when subject to cavitation. A photocell, used to detect the transient strains, indicated that the time duration of the strains was about 2 microseconds. Using an ultra-high-speed motion picture camera, ultrasonic cavitation bubbles have been photographed collapsing on the surface of a photoelastic specimen, and the resulting strain wave in the solid has been photographed. The dynamic properties of a photoelastic material have been obtained in order to permit quantitative interpretation of the transients. This has indicated that the stresses due to cavitation may be as high as 2.8 x 10^5 psi. The photoelastic plastic, CR-39, was found to exhibit strain birefringence, and its strain-optic constant was found to be independent of the rate of loading.

ID: CaltechAUTHORS:20150505-154123455

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Abstract: This paper investigates in a rather idealized way the different properties of fully cavitating and fully wetted hydrofoils in order to clarify the relative hydrodynamic merits of each insofar as this is possible in the present state of the art. The discussion is mainly based on a recent theory, together with some experimental data, on the hydrodynamics of two-dimensional fully cavitating hydrofoils. A number of quantitative comparisons between the fully cavitating and fully wetted two-dimensional foils have been made to bring out the different effects of such design parameters as attack angle, camber, submergence and speed on the hydrofoil in the two regimes. In addition, some of the effects which modify the two-dimensional comparison are surveyed and roughly estimated wherever possible. The consequences of air ventilation (which is closely related to fully cavitating flow) are discussed, especially as applied to the supporting struts, from the standpoint of whether or not it should be avoided. Finally, after a few remarks on some practical aspects of the problem, a rough comparison is made from the economy point of view to indicate by an example how a criterion might be chosen for one or the other type of operation. From this and the preceding calculations it is conjectured that there is strong reason to believe that the fully cavitating type of operation will be advantageous in some circumstances, but it is emphasized that more experience must be accumulated for operation in both regimes before any practical criteria can be specified.

ID: CaltechAUTHORS:WUThydrolabrpt47-4

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Abstract: This report summarizes about three years of experimental work on centrifugal pump impellers by the hydraulic machinery group of the Hydrodynamics Laboratory. Some of the work discussed herein has already been reported as individual investigations by this project. This report embodies these earlier results together with more complete and recent investigations of centrifugal pump impellers.

ID: CaltechAUTHORS:20150603-111644987

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Abstract: The problem of cavity flows received attention early in the development of hydrodynamics because of its occurrence in high speed motion of solid bodies in water. Many previous works in this field were mainly concerned with the calculation of drag in a cavitating flow. The lifting problem with a cavity (or wake) arose later in the applications of water pumps, marine propellers, stalling airfoils, and hydrofoil crafts. Although several formulations of the problem of lift in cavity flows have been pointed out before, these theories have not yet been developed to yield general results in explicit form so that a unified discussion can be made. The problems of cavitating flow with finite cavity demand an extension of the classical Helmholtz free boundary theory for which the cavity is infinite in extent. For this purpose, several self-consistent models have been introduced, all aiming to account for the cavity base pressure which is in general always less than the free stream pressure. In the Helmholtz-Kirchhoff flow these two pressures are assumed equal. Of all these existing models, three significant ones may be mentioned here. The first representation of a finite cavity was proposed by Riabouchinsky in in which the finite cavity is obtained by introducing an "image" obstacle downstream of the real body. A different representation in which a reentrant jet is postulated was suggested by Prandtl, Wagner, and was later considered by Kreisel and was further extended by Gilbarg and Serrin. Another representation of a free streamline flow with the base pressure different from the free stream pressure, was proposed recently by Roshko. In this model the base pressure in the wake (or cavity) near the body can take any assigned value. From a certain point in the wake, which can be determined from the theory, the flow downstream is supposed to be dissipated in such a way that the pressure increases gradually from the assigned value to that of the free stream in a strip parallel to the free stream. Apparently this model was also considered independently by Eppler in some generality. Other alternatives to these models have also been proposed, but they do not differ so basically from the above three models that they need to be mentioned here specifically. The mathematical solutions to the problem of flow past a flat plate set normal to the stream have been carried out for these three models. All the theories are found to give essentially the same results over the practical range of the wake underpressure. That such agreement is to be expected can be indicated, without the detailed solutions for the various models, from consideration of their underlying physical significance, as will be discussed in the next section. In the present work the free streamline theory is extended and applied to the lifting problem for two-dimensional hydrofoils with a fully cavitating wake. The analysis is carried out by using the Roshko model to approximate the wake far downstream. The reason for using this model is mainly because of its mathematical simplicity as compared with the Riabouchinsky model, or the reentrant jet model. In fact, it can be verified that these different models all yield practically the same result, as in the pure drag case; the deviation from the results of one model to another is not appreciable up to second order small quantities. The mathematical considerations here, as in the classical theory, depend on the conformal mapping of the complex velocity plane into the plane of complex potential. By using a generalization of Levi-Civita's method for curved barriers in cavity flows, the flow problem for curved hydrofoils is finally reduced to a nonlinear boundary value problem for an analytic function defined in the upper half of a unit circle to which the Schwarz's principle of reflection can be applied. The problem is then solved by using the expansion of this analytic function inside the unit circle together with the boundary conditions in the physical plane. In order to avoid the difficulty in determining the separation point of the free streamline from a hydrofoil with blunt nose, the hydrofoils investigated here are those with sharp leading and trailing edges which are assumed to be the separation points. Except for this limitation, the present nonlinear theory is applicable to hydrofoils of any geometric profile, operating at any cavitation number, and for almost all angles of attack as long as the wake has a fully cavitating configuration. As two typical examples, the problem is solved in explicit form for the circular arc and the flat plate for which the various flow quantities are expressed by simple formulas. From the final result the various effects, such as that of cavitation number, camber of the profile and the attack angle, are discussed in detail. It is also shown that the present theory is in good agreement with the experiment.

ID: CaltechAUTHORS:HydroLabRpt21-17

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Abstract: The effect of the free surface on the pressure distribution on the upper side of a shallow-running hydrofoil is considered from a general point of view. Previous theoretical and experimental work is reviewed in order to compare the range of flow variables for which each treatment of the surface proximity problem is valid. A qualitative theoretical expression for the pressure is developed. This result shows the relative importance of the pertinent parameters and it is shown to agree qualitatively with previous experiments as well as with new pressure measurements made in the Free Surface Water Tunnel. The above considerations reinforce the view generally held in the past, that the methods of potential theory when properly applied to hydrofoils at shallow submergences may be expected to lead to valid and useful results.

ID: CaltechAUTHORS:PARhydrolabrpt47-2

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Abstract: An experimental study of volute influence on radial flow impeller performance was conducted by operating a single impeller with three different sets of volute vanes. In each case, over-all performance was measured and internal flow study within the volute was made. The results show that at their respective design flow rates the influence of the volutes is least and the deviation of performance from the free impeller operation is small. At off-design flow rates there are major changes in the impeller performance due to the presence of the volutes. Large real fluid effects, coupled with a quite nonuniform velocity pattern at the impeller exit, result in a flow through the volute that does not resemble a potential flow. Even so, the fluid losses through the volute are comparatively small. It is also shown that at off-design conditions, the flow cannot be irrotational and therefore potential flow theories cannot be used in describing the flow or predicting performance.

ID: CaltechAUTHORS:20150529-143343010

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Abstract: A study of turbulence in a water tunnel was made by observing the motion of small liquid droplets having the same density as water. These tracers were injected into the flow and their trajectories were photographed with a fixed camera using a stroboscopic light. From measurements of the photographic plates it was possible to calculate instantaneous velocities, turbulence intensities and Lagrangian correlation coefficients. Runs were made both with and without a turbulence-producing grid; three geometrically similar grids were used. From 11 to 35 separate trajectories were measured for each run. Each point value of the turbulence characteristics is an ensemble average. The biggest limitation on the practical application of this method is the inevitable sampling error in the calculated intensities and correlations. These errors were large, even when 35 trajectories were measured; they can be reduced only by greatly increasing the number of trajectories analyzed. A satisfactory experimental technique for photographing and measuring the trajectories of the tracers was developed, but the computations are still very laborious. The results of the study showed that a large fraction of the turbulent energy of the field may be attributed to substantial differences between the mean velocities of different tracers over the 3-ft observation reach. The decay of turbulence energy with distance showed a linear relation between the reciprocal of the energy and the distance, as has been previously found, but a strong Reynolds number effect was observed. The correlation curves indicated that the time scale was fairly large, and it appeared that practically all the energy was associated with relatively low frequencies. Unfortunately, the data were not extensive enough to permit calculation of the diffusion coefficients from the Lagrangian correlations in accordance with Taylor's theory.

ID: CaltechAUTHORS:20150526-163641943

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Abstract: An experimental program was initiated in the High Speed Water Tunnel to measure force coefficients for hydrofoils under cavitating conditions. This program necessitated either a new force balance or a major modification of the existing one. Various balance configurations and pressure seal designs which were considered are described. A balance modification design was selected which consists of an appendage bolted between the existing balance and the water tunnel working section. This appendage alters the basic geometry of the force balance so that the model is now mounted on a parallelogram linkage instead of on a simple pivoted lever. The addition of the parallelogram force table suspension to the old balance renders the modified balance unresponsive to moments which in the old balance, interacted with forces and resulted in errors in the force readings. This modification which is described in detail was accomplished and resulted in a successful force balance capable of accurate measurement of forces on cavitating and noncavitating hydrofoils; and, in fact, it is expected to replace the old force balance for all force measurement work in the High Speed Water Tunnel. The cost and construction time for the balance modification were considerably less than would have been required for an entirely new force balance of comparable accuracy and sensitivity.

ID: CaltechAUTHORS:HydroLabRpt-47-1

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Abstract: Most types of problems which arise in connection with the use of a hydrofoil operating in water can be solved simply by treating it as an airfoil operating in air. For this purpose, use can be made of the great wealth of theoretical information and experimental data which can be found in the literature. There are, however, regimes of operation of the hydrofoil which are not duplicated by the airfoil excepting possibly under very special conditions. These regimes are identified by one of the following: (a) cavitation (b) ventilation (c) proximity to a free surface Cavitation is characterized by the presence of water vapor bubbles at regions in the flow where the pressure is less than the vapor pressure corresponding to the existing water temperature. Although most commonly observed on the blades of propellers or on the vanes of axial flow pumps, cavitation can also be present on fins used to stabilize high speed underwater missiles, on hydrofoils used as lifting surfaces, or on support struts of various kinds. Allied to this problem is ventilation, a condition which is like cavitation in that it results in discontinuities in density in the fluid surrounding the hydrofoil, although the initiating mechanism is fundamentally different and the lighter medium is air or gas instead of water vapor. A third type of flow regime which may be very important is that associated with a hydrofoil which approaches or intersects a water-vapor or water-gas interface. In this case the flow must satisfy the constant pressure boundary condition on that interface. The effect of gravity may or may not be important, and the hydrofoil can be oriented in any direction. A lifting hydrofoil would most likely be parallel, or nearly parallel, to the water surface, whereas a support strut or a stabilizing fin would inter sect the water surface nearly at right angles. It is this last mentioned type of ope ration which is investigated in this report, and which, as will be seen later, also implies a study of the effects of air ventilation. Among the specific fundamental questions which arise in considering a vertical hydrofoil piercing a flat water surface and which is at an angle of attack to the flow, are the following: (a) How does the presence of the air-water interface affect the apparent aspect ratio of the hydrofoil as compared with its geometrical value? (b) What is the effect of air ventilation on the value of cross-force developed by the hydrofoil, and what observations can be made regarding the inception of this phenomenon? Since no previous hydrofoil studies had been performed in the Free Surface Water Tunnel, it was also of interest to determine the suitability of that facility and its associated equipment for doing work of this kind. On the other hand, the investigation was intended only as a preliminary one and was, therefore, undertaken with limited resources.

ID: CaltechAUTHORS:20150529-155238982

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Abstract: Water tunnel measurements were made on rectangular bar and circular cylinder struts piercing the free water surface. These were run at several depths and velocities in order to measure drag forces and to investigate the mechanism by which air often ventilates down behind such struts. It was found that the ventilation mechanism depends on viscous wake phenomena in a manner similar to ventilation behind fully-submerged bodies. Moreover, in fully-ventilated flow the forces are well predicted by application of two-dimensional cavity theory. A hysteresis effect on ventilation and forces was observed and found to be caused by surface tension. This last may explain some discrepancies between the present drag data and that previously taken on circular cylinders in a towing tank.

ID: CaltechAUTHORS:20150526-135328932

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Abstract: This memorandum is to list technical reports prepared under Contract No. N6onr-24424 during its life, which extended from April 1, 1949 through April 30, 1954. As may be seen from the report titles listed below, the research dealt almost exclusively with the dynamics of underwater bodies running in open cavities. A major portion of the work dealt with the basic hydrodynamics of this type of flow, and hence was unclassified. However, part of the work which dealt with some of the more specialized aspects of the problem was, of necessity, classified. In all, eight unclassified reports and five classified reports were prepared. Mr. J. P. O'Neill was in charge of the studies during the active life of the project, and, as may be seen from the report authors, he was ably assisted by several active workers, principal among whom were the following: Messrs. Byrne Perry, Taras Kiceniuk, W. M. Swanson and Dr. E. Y. Hsu.

ID: CaltechAUTHORS:20150518-155330444

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Abstract: A theory is developed which describes the behavior of a vapor bubble in a liquid. Its physical basis is the assumption that the heat transfer effects which accompany the evaporation occurring at the bubble wall when the bubble grows, 0r the condensation that occurs there when the bubble collapses, are dynamically important. The basic equations of hydrodynamics are shown to reduce, for the problem under consideration, to a dynamic equation which describes the behavior of the bubble wall, and a heat convection equation for the liquid which is coupled to the dynamic equation by a boundary condition at the bubble surface. A solution for the heat problem is obtained under the assumption that significant temperature variation in the liquid occurs only in a thin thermal boundary layer surrounding the bubble wall. An estimate of the correction to the temperature solution is also derived. Once the temperature at the bubble wall is given, the vapor pressure within the bubble is known and the dynamic problem becomes determinate. The theory is applied to the cases of the growth of a vapor bubble in a superheated liquid, and the collapse of a vapor bubble in a liquid below its boiling temperature at the external pressure. The simplifying physical assumptions made in the course of the investigation are justified for the specific example of vapor bubble behavior in water. A comparison of the theory with experiment is given for the observable range of bubble growth in superheated water, and the agreement is found to be very good.

ID: CaltechAUTHORS:20150527-150855100

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Abstract: For the past twenty-four months this Laboratory has been engaged in a study of wave action on barriers. The first half of this investigation was limited to cases of wave reflection from various structures. The experimental program for this first phase of the investigation included both the development of instrumentation and experimental techniques and the measurement of wave forces and pressures acting on plane barriers inclined at various angles and on a family of curved and stepped-face barriers selected by the Bureau of Yards and Docks. The results of that program (Refs. 1 and 2) include: (1) The development and experimental verification of relatively simple analytical expressions for the force and pressure distributions exerted on vertical plane barriers by reflecting waves. These expressions include a second-order double wave frequency term which becomes of increasing importance for small values of L/d (wavelength to water depth ratio), and which has not heretofore been considered in connection with wave forces on barriers. (2) The demonstration of a simple relationship between the forces acting on a vertical plane barrier and those acting on plane barriers inclined at angles up to 30° from the vertical, and on certain curved and stepped-face barrier profiles. The extension of the program to include the study of breaking waves was a logical consequence of the earlier work, both because of the engineering importance of the breaking wave problem and because the apparatus and experience developed in the first phase promised to be directly applicable to such a study. Previous knowledge of the breaking wave problem was limited almost solely to analysis and measurements of the impulsive or shock pressures developed by breaking waves. Since these short-duration, high-intensity pressures appear in some respects to be unrealistic as the basis for design, this investigation approached the problem by determining the force-time history during the entire wave cycle to permit the evaluation of other aspects of the force function than the singular one of initial impulse. The study was necessarily restricted to a few values of geometric and wave parameters, but the results, as expressed in dimensionless parameters, promise to provide useful data for a wide range of design problems. These results include: (1) Determination of wave steepness and water depth parameters which result in wave breaking for various plane barrier and foreshore geometries. {2) The correlation of measured breaking wave impulse with computed wave momentum derived from solitary wave theory. {3) Experimental determinations of the relationship between wave parameters and the magnitude and location of a maximum effective force believed valid for design purposes, expressed in terms of the computed wave momentum.

ID: CaltechAUTHORS:20150603-140715905

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Abstract: Contract NOy-12561 was initiated 28 June 1945 for the purpose of conducting hydraulic model experiments to guide the extensive harbor improvements then in process and planned for, at Apra Harbor, Guam, M. I. The contract was continued through change orders and finally terminated on 30 November 1954. The Apra Harbor investigation was completed at the end of 1948, and during the following contract period activity was directed along the lines of basic investigations of wave phenomena as they affect harbors and harbor structures. The program of the Laboratory was formulated and directed by Robert T. Knapp, Professor of Hydraulics, during the Apra Harbor studies and those immediately following. During this time laboratory facilities were designed and procured and the general program, which was followed by the project until its completion, was delineated. Dr. Warren O. Wagner was supervisor of the project during most of the Apra Harbor study. From the spring of 1949 until the termination of the contract, the project was supervised by Mr. John H. Carr. In the following sections of this report, the aim and procedure of the several investigations are outlined, and the principal results summarized.

ID: CaltechAUTHORS:20150506-101300963

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Abstract: The expressions for kinetic and strain energy for longitudinal stress waves in a bar are considered, first in a one-dimensional model in which cross sections are assumed to remain plane, and stresses in the radial and circumferential direction are assumed to be zero. From this, an equation of motion is derived which is used to determine the speed of longitudinal sinusoidal stress waves as a function of wave length. Secondly, a simplified three-dimensional model is considered where the axial motion is a parabolic function of the radius, from which the speed of sinusoidal stress waves is derived. The derived expressions are compared with previously published solutions.

ID: CaltechAUTHORS:20150505-152252618

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Abstract: The steady two-dimensional sink-type flow of a viscous, heat-conducting perfect gas is investigated. An approximate solution of this problem is given for the case of large Reynolds number Re (cf. the definition given in the text). In obtaining the present solution the values of Prandtl number and the ratio of the first and second viscosity coefficient may be arbitrary. The result shows that the solution has two branches, both of physical significance. On the subsonic branch of the solution the flow speed starts from the stagnation point at infinity, increases monotonically for decreasing radial distance and eventually terminates with maximum speed at a certain point inside the inviscid sonic circle. The solutions of the supersonic branch, which start with the maximum speed at infinity, all contain cylindrical shocks. Within the shock the flow speed assumes a minimum value and after the shock all solutions tend asymptotically to the subsonic branch. In contrast to the plane shock, the cylindrical shock strength is limited to the order O(Re^-1/3), and the shock-thickness, of O(Re^-2/3) The latter quantity implies that the thickness of the region in which the viscous effects are important is thinner, in order of magnitude, than that of ordinary boundary layer (of O(Re^-1/2)) but is thicker than that of plane normal shock (of O(fRe^-1)). It is found that the entropy of the super sonic branch rises to a maximum within the shock while for the subsonic branch, the entropy increases monotonically with the radial distance. The total variation of the entropy across the shock is found to be of O(Re^-2/3) which is in general greater than that across a plane normal shock (~O {shock strength}^3). The effect on the flow quantities due to the variation in viscosity coafficients, assumed to depend on the local temperature, is found to be at most of O(Re^-2/3).

ID: CaltechAUTHORS:HydroLabRpt21-16

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Abstract: An experimental investigation of flow between the shrouds of an impeller has shown that gross flow separation can occur for "well designed" shapes. Rotation of the shrouds inhibits separation and if the flow coefficient is sufficiently low it will be completely prevented. For the particular impeller shroud profile studied it was found that the velocity distribution in the inlet regions (near where the impeller inlet edge would be placed) is satisfactorily approximated by potential theory. Potential flow velocity distributions on several families of shroud shapes suitable for impeller or supercharger design are then given for use in design.

ID: CaltechAUTHORS:20150603-152046517

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Abstract: In the present investigation the models, comprising a family of cones of varying apex angle, were mounted below the surface of a moving body of water on a three-component force balance, thereby permitting lift, drag and pitching moment to be measured.

ID: CaltechAUTHORS:KIChydrolabrptE-12-17

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Abstract: Experimental investigations of the effects of jets and exhaust on a model of the TTV Mk 40 X-1 are discussed. Photographs of the model jet and exhaust flow patterns are presented. Model pressure distribution data and afterbody drag coefficients are shown for numerous flow conditions. Many correlations among the observed phenomena are discussed. Several estimates of prototype jet- and exhaust-induced drag forces are presented. The susceptibility of the configuration to cavitation is discussed. Detailed analyses of the model results as they pertain to the prototype external flow phenomena are presented. Possible fields of study are suggested which could lead to improved prototype performance characteristics.

ID: CaltechAUTHORS:20150604-161127581

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Abstract: Because of the need for design information for seaplanes and planing boats, the hydrodynamics of planing has been the object of much experimental and some theoretical study in the last twenty-five years. More recently the subject has become of interest in the field of hydroballistics. For practical purposes the chief source of information has been the extensive tests made with small models in towing tanks, both on specific hulls and on simple geometric forms. These latter tests are useful for under· standing the basic phenomena of planing, and experiments on flat plates have been particularly helpful in this respect. An immediate question for the experimenter is the nature and magnitude of the so-called scale effect, if any, which may appreciably influence the test results. The term "scale effect" as used in planing work includes both viscous and surface tension effects, but not gravity effects, which are modeled by maintaining the proper Froude number. The problem was first considered by Sottorf, who carried out a systematic series of tests on flat plates of different scale at a constant Froude number. Sottorf concluded that the hydrodynamic pressure distribution on the plate was not noticeably affected by scale, while the shear forces, on the other hand, were very sensitive to the size of model, both because of the usual viscous effects and also because of the alteration of the flow near the edges by surface tension. Thus, although the force parallel to the plate, which largely determines the drag at small attack angles, cannot be modeled properly, the force normal to the plate {or for small angles, the lift force) is unaffected by scale so long as the proper Froude number is maintained. In spite of Sottorf's conclusions on this point, however, there have recently been expressions of doubt as to the validity of lift force measurements made with small models. For example, some tests made by Falkemo and Adlercreutz have been reported3 in which the measurements on a model 5 inches wide were of the order of 20% higher than that value predicted from an empirical formula based on Sottorf's data. The discrepancy was ascribed to scale effect though Sottorf had successfully used a model of 3-in. width for a similar measurement. In view of the importance of small models in planing work, a program of systematic tests on scale effect has been initiated in the Free Surface Water Tunnel of the Hydrodynamics Laboratory. The results of tests on flat plates to date are reported herein.

ID: CaltechAUTHORS:20150518-161855523

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Abstract: A program of experimental work on air-supported cavity flow has been in progress in the Free Surface Tunnel for some time now and a considerable amount of data has been taken. Most of this work has been concerned with cones and disks, which have distinct points at which the cavity separates from the nose, but it was thought worthwhile to extend the investigations to include continuously curving noses with shapes such as spheres and ellipsoids. As a start in this direction, a number of tests have been made on spheres with attached cavities. The sphere was selected as a convenient shape because of its simplicity, the availability of models already made up, and the possibility of comparing results with those of other investigators. The purpose of the present note is to report the test data taken so far; detailed analysis and comparison will be postponed for a future report.

ID: CaltechAUTHORS:20150507-164943223

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Abstract: The first occurrence of noise in an axial flow pump is correlated with the visually observed inception of cavitation for a range of tip clearances and flow rates. The magnitude of the sound level in the machine is determined as a function of the cavitation number for several tip clearances. However, the peak sound level does not depend much on tip clearances, and is about 35 db. above the ambient level.

ID: CaltechAUTHORS:20150526-133304491

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Abstract: The theoretical problem of predicting the course which a ship follows 1n response to a prescribed stern-plane or rudder motion has not been satisfactorily solved. A satisfactory solution of this problem would have considerable practical value, particularly for the motion of a submarine where "maneuverability in depth" is so important. The theory is unsatisfactory in the sense that trajectories describing the motion cannot reliably be predicted from the results of captive model tests. The commonly accepted reason for this failure is that the hydrodynamic characteristics which are determined from captive model tests are not known with sufficient precision or reliability. This reason is quite plausible in view of the discrepant results which are often obtained from different model tests of the same prototype. The present study was undertaken with the object of ascertaining whether it is possible to combine information from captive model tests with information from free-running model tests for the purpose of constructing hydrodynamic characteristics which may be introduced into differential equations of a given form, such equations being used to characterize the motion, and thus allowing one to predict new trajectories. Only hand computation methods have been used in this investigation. Although no very fixed conclusions can be drawn, it appears that more accurate free-running tests (as well as captive model tests) are required to obtain positive results. However, it is misleading to imply that nothing of value can be learned from this type of approach. One can, in fact, roughly predict some trajectories and, given enough patience, one could, perhaps, continue to modify the equations so that they fit more and more trajectories. It is known that nonlinear differential equations must be used to characterize the motion and it is, therefore, evident a priori that theoretically there must always exist some ambiguity regarding the validity of the equations. However, from a practical point of view one may say that if equations have been constructed which have as one solution a given trajectory, then these equations should be approximately valid for trajectories which are not too different, i.e., trajectories which do not involve a different type of maneuver and do not involve large differences in the magnitudes of any of the parameters which directly influence the motion.

ID: CaltechAUTHORS:20150521-142153408

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Abstract: An experimental investigation of the effect of the boundary layer on cavitation inception for a smooth streamlined body of revolution is described. The influence of air diffusion upon the observed results is also discussed, In addition, this study has shown that tensions exist in the flow of ordinary water at incipient cavitation.

ID: CaltechAUTHORS:20150521-144133631

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Abstract: The results of an experimental program carried out in the High Speed Water Tunnel to measure the forces on a cylinder planing on the inside surface of a vapor cavity are pre sen ted. Curves of lift, drag, and pitching moment coefficients and position of the center of pressure of the planing cylinder are given as functions of planing angle and draught. A brief description of the vapor cavity, spray configurations, and cylinder cavitation are included.

ID: CaltechAUTHORS:20150506-103605454

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Abstract: Recent experimental work has concentrated on the study of resultant force and pressure distribution on the stepped barrier designated as Case 5 (W. M. Simpson, Serial 1057, 6 Aug 1953 / J. H . Carr). Case 5 barrier has a plane vertical front face extending the two feet from bottom to still-water surface. Above still-water level are five steps, each of 2. 4-in. rise and tread. These dimensions, to a 20:1 scale, represent the prescribed prototype depth of 40 feet and the rise and tread of four feet each. The separate model barriers for resultant force and for pressure distribution measurements are each cast of aluminum. Vertical ribs at the rear provide rigidity and serve as convenient mounting surfaces.

ID: CaltechAUTHORS:20140530-141215670

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Abstract: Recent experimental work has concentrated on the study of resultant force and pressure distribution on the stepped barrier designated as Case 5 (W. M. Simpson, Serial 1057, 6 Aug 1953 / J. H . Carr). Case 5 barrier has a plane vertical front face extending the two feet from bottom to still-water surface. Above still-water level are five steps, each of 2.4-in. rise and tread. These dimensions, to a 20:1 scale, represent the prescribed prototype depth of 40 feet and the rise and tread of four feet each. The separate model barriers for resultant force and for pressure distribution measurements are each cast of aluminum. Vertical ribs at the rear provide rigidity and serve as convenient mounting surfaces.

ID: CaltechAUTHORS:20140702-103335360

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Abstract: A qualitative study of the effects of cavitation on the performance of an axial flow pump was n1ade. Photographic evidence shows that cavitation need not occur first on the blade surface but could occur in the free stream. This phenomenon is ascribed to a flow through the tip clearance space. Cavitation similarity was found to be determined by the cavitation number K, Thoma's σ, or the suction specific speed S for the conditions of these tests.

ID: CaltechAUTHORS:20150506-152851465

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Abstract: In studies concerned with the application of pumps to underwater jet propulsion, it has been pointed out that cavitation may be avoided or suppressed by enclosing the pump (or propeller) in a suitably shaped shroud. The advantages of avoiding cavitation are clear; namely, the elimination of much noise, damage and vibration in addition to increasing the allowable speed. However, a general discussion of the various flow processes which lead to cavitation is not yet possible. For propellers, cavitation is observed in helical trailing vortices and also on the blade surface proper, but for other types of propulsion systems, notably pump jets, neither is the location known nor the cause completely understood. Roughly speaking, cavitation will occur when local pressures reach the vapor pressure of the flowing liquid, however, the magnitude and location of these local underpressures depend upon the complete history of the flow as it passes through the machine. Consequently, minimum pressures may occur in the free stream in some cases, or upon the blade surface itself in others. Thus, in order to study cavitation phenomena, it is first necessary to investigate the detailed behavior of the flow. Apart from cavitation and noise, there are also other problems of considerable importance in rotating axial flow machinery. Among the most prominent of these is the behavior of the fluid in the boundary layer near the rotor and stator blade tips, and the off design performance in the region of stalled flow. These questions are of great concern in the design and application of axial flow compressors and, as long as compressibility effects are negligible, they may be investigated just as well in water as in air. Moreover, inasmuch as the kinematic viscosity of air to that of water is thirteen to one {at atmospheric conditions), machines can be made to operate in water at the same Reynolds numbers as in air at much reduced speeds, sizes, power consumptions and blade stresses, and as a result of these facts the installation and operational costs are also lower than for the comparative air machine. The cost of the blading of a compressor is a major portion of the total cost of the machine and, therefore, the high expense of installing different blade designs for research purposes prohibits extensive investigation. In 1951 the Hydrodynamics Laboratory at the California Institute of Technology developed a method of making inexpensive precision lead-alloy blades for axial flow pump test impellers. As a result of this work, interest was expressed by personnel of the Naval Ordnance Test Station and staff members of the Institute in the application of such blade-making techniques for air compressor and underwater propulsion research. It was estimated that blades could be made for about one-eighth of the cost per blade row of those in a research compressor currently operating at the Institute. This attractive estimate lead to the consideration of an axial flow compressor run in water as a pump at relatively low speeds so that research on cavitating and noncavitating flow could be done without prohibitive expense. Under this contract, NOrd 9612, an axial flow pump with its enclosed circuit was constructed and preliminary tests on a single stage of blading were run by the first week of November, 1952. It is the purpose of this report to describe the installation and show its usefulness for research.

ID: CaltechAUTHORS:20150506-102839661

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Abstract: This report describes a study conducted jointly by the Hydrodynamics Laboratory of the California Institute of Technology and the Pasadena Annex of the Naval Ordnance Test Station, Inyokern. Air to water launchings were made with a full-size (22.42-in. dia.) dummy Mk 25 aircraft torpedo with a 3-l/2-cal. 70° spherogive nose and with a 2-in. dia. model of the same shape. The purpose of this investigation was to study the problems associated with water entry modeling. Froude scaling was used to determine model entry velocity and the air pressure in the model system was reduced until the cavitation number of the model equaled that of the prototype. Equal cavitation number and equal Froude number scaling was found to be adequate as long as a turbulent boundary layer existed in the flow around the model. When the entry velocity of the model was low enough for a laminar boundary layer to occur, the trajectory of the model deviated from that of the prototype beyond 35 diameters of underwater travel. It was then necessary to induce turbulence in the boundary layer by roughening the nose of the model before successful modeling could be achieved. The tests made during this investigation were with the following entry conditions: Entry Velocity prototype - 200 fps and 400 fps model - 60, 80 and 120 fps Air Pressure prototype - l atm. model - l, 1/ll and l/21 atm. Air Trajectory prototype and model - 22° Entry Pitch Angle prototype - 0 to 6° nose up model - 3° nose down to 6° nose up

ID: CaltechAUTHORS:20150507-152317635

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Abstract: The program of this report is as follows: After a brief survey of the available theoretical and experimental information on the characteristics of hydrofoils, the theory for a hydrofoil of finite span will be formulated. The liquid medium is assumed to be incompressible and nonviscous and of infinite depth. The basic concept of the analysis is patterned after the famous Prandtl wing theory of modern aerodynamics in that the hydrofoil of large aspect ratio may be replaced by a lifting line. The lift distribution along the lifting line is the same as the lift distribution, integrated with respect to the chord of the hydrofoil, along the span direction. The induced velocity field of the lifting line is then calculated by proper consideration of lift distribution along the lifting line, free water surface pressure condition and wave formation. The "local velocity" so determined for flow around each local section perpendicular to the span of the hydrofoil can be considered as that of a two-dimensional flow around a hydrofoil without free water surface. The only additional feature of the flow in this sectional plane is the modification of the geometric angle of attack, as defined by the undisturbed flow, to the so-called effective angle of attack on account of the local induced velocity. Thus the local sectional characteristics to be used can be taken as those of a hydrofoil section in two-dimensional flow without free water surface but may involve cavitation. More precisely, the hydrofoil section at any location of the span has the same hydrodynamic characteristics as if it were a section of an infinite span hydrofoil in a fluid region of infinite extent at a geometric angle of attack equal to ae, together with proper modification of the free stream velocity. Such characteristics may be obtained by theory or by experiment and should be taken at the same Reynolds number and cavitation number. With this separation of the three-dimensional effects and the two-dimensional effects, the effects of Froude number are singled out. Thus a systematic and efficient analysis of the hydrofoil properties can be made.

ID: CaltechAUTHORS:WUYhydrolabrpt26-8

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Abstract: [no abstract]

ID: CaltechAUTHORS:20140701-154118017

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Abstract: Change Order "O" to Contract NOy-12561, under which the Laboratory is now operating, provides as a general objective the investigation of the forces and pressures exerted by waves on fixed plane barriers inclined at any angle to the sea surface, and on stepped or off-set plane barriers. In keeping with this objective, the Laboratory is endeavoring to develop a program which will combine a basic investigation of the mechanics of wave-induced forces with the production of immediately useful data. It is expected, for instance, that the results of experimental farce and pressure measurements on plane barriers, aside from their scientific value, can be used with profit in calculating the stability of gravity-type or caisson breakwaters against sliding and overturning. Since this program represents a new field of work for this Laboratory, the initial portion of the contract period has been devoted to the alteration of existing laboratory equipment, and the design and construction of required new equipment. In all of the~ modification and development of force and pressure measuring equipment, an effort has been made to design for maximum flexibility. Thus, the resulting basic units can be easily adapted to the various specific phases of the current or future investigations, such as breaking and non-breaking wave conditions, and many configurations of structures for which force or pressure data will be of interest. At this time, all equipment for the pressure measuring and orbit investigation programs has been completed, and work on these programs has begun. The force measuring apparatus is under construction, with completion estimated as June 1, 1953. In view of the considerable investment in time and funds made to equip the Laboratory for this new type of investigation, this report has been prepared to describe in some detail the alteration of existing equipment and the development of new equipment.

ID: CaltechAUTHORS:20140603-145041602

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Abstract: Preliminary observations of the behavior of submerged steam nozzles discharging into stationary and moving water are described, and photographs ate presented to show the changes in appearance of the steam jet due to changes in chamber pressure and/or water velocity. The measured static pressure distributions along the longitudinal axis of both a converging nozzle and one of the de Laval type have been plotted showing the contrast between the operation of a steam nozzle discharging into air and that of one submerged in water. A missile running in an air-supported cavity was studied to determine the effect of the discharge of a condensable-jet propulsion unit upon the over-all size and shape on the cavity sheath surrounding the missile; a comparison was made with former experiments in which the propulsion unit used a noncondensing gas for the propellant. The appendix presents the results of a preliminary study of the thrust augmentation effect suggested by Gangwer which is intended as a means for reducing the depth sensitivity of rocket propulsion units operating at high speeds.

ID: CaltechAUTHORS:20150506-164818645

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Abstract: Experimental observations are made on collapsing cavitation bubbles. Bubbles generated by two different methods are studied. The first method consists of bubble generation and collapse by flow over a submerged body. This work is done in the High-Speed Water Tunnel of the Hydrodynamics Laboratory. Existing photographic equipment and experimental techniques are employed. The second method consists of bubble generation and collapse by variation of the hydrostatic pressure. Much improved time and space resolution of the collapse is obtained in the latter case by design and construction of a high-speed photographic system. Bubble collapse pictures are taken at 10^5 frames per sec and an effective exposure time of 5 x 10^(-8) sec. A magnification of eight diameters fro.m object to image is attained. This equipment reveals new details of cavitation bubble collapse. Numerical solutions of the spherical bubble collapse equations are compared with experimental results. A consistently longer collapse time is observed in all cases. Observed bubble asymmetries are shown to be caused by pressure gradients. A large degree of coupling 1s shown to exist between the radial motion and the translational motion of the bubble centroid. Bubble collapse is observed to be much less stable than bubble growth.

ID: CaltechAUTHORS:20150527-141321349

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Abstract: Drag studies were made on a series of models having varying degrees of bluntness and varying length-to-diameter ratios. Using the drag coefficients obtained from the tests, terminal sinking velocities in sea water were calculated for various volumes and densities. It was found that the terminal sinking velocity of a blunt-nosed body could be increased 15 percent if the length-to-diameter ratio was increased from 7 to 14 for the same volume. The terminal sinking velocity of a fine-nosed body could be increased only 2 percent if the length-to-diameter ratio was increased from 6 to 12.

ID: CaltechAUTHORS:20150506-102521292

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Abstract: An analytical study, combining jet diffusion patterns and jet velocities, indicates that there are four methods of eliminating the clinging jet phenomenon which occurs on the Mk-40 Torpedo Test Vehicle. It is shown that extension of the nozzles along the existing nozzle axis appears to present the simplest method of design improvement. Experiments were conducted on a modified model of the Mk-40 to verify the analysis. It was found that for the operational jet-to-model velocity ratio, (U/V) of 2, a nozzle extension of 6 nozzle diameters is the minimum required to provide cling-free performance. All experiments and calculations were made for the case of a body without exhaust ports or gas discharge.

ID: CaltechAUTHORS:20150506-102103438

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Abstract: Previous theories and empirical formulas for the lift of flat planing surfaces are reviewed, and the resemblance of the planing surface to the airfoil noted, A simple expression, which converges to the correct limits for exactly known cases, is assumed for the ratio of planing to airfoil lift, and the planing lift is then estimated by using airfoil experimental data. The resulting calculated values are in satisfactory agreement with planing experiments.

ID: CaltechAUTHORS:20150506-164503104

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Abstract: Force measurement runs were made on a model MK 13-2 Torpedo to correct previously reported results for the discrepancies which were attributable to the interaction of pitching moment on the force measuring apparatus. The plain body, the body with fins, and the body with a shroud ring tail were tested at yaw angles of -10 degrees to +10 degrees. Drag-force coefficients, cross-force coefficients, and yawing moment coefficients were calculated and are presented in this report.

ID: CaltechAUTHORS:20150529-143850147

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Abstract: When it is expected that the afterbody of a projectile will plane on the free surface of an open cavity, the lift coefficient of the planing shape is of primary concern to the projectile design engineer. To provide basic data applicable to the design of an afterbody subject to such planing conditions, lift coefficients have been determined for a family of rings planing on a flat water surface. Changes in chord-diameter ratio and in flare angle were the model variables while angle of attack and submergence were varied during the course of the measurements of lift force. In order to eliminate strut and afterbody configuration as a further necessary variable in the present tests, the models were supported from the top so as to minimize interference with the basic flow pattern produced by a simple ring. All ring edges were cut perpendicular to the ring axis and lap finished to a blunt and sharp cornered configuration that could be easily reproduced. Photographs of typical test conditions are included in this report so that the proper flow configuration can be associated with various points on the plots of lift coefficient. With judicious selection from the graphs, and careful consideration of the flow pattern, it should be possible to gain insight into the lift forces that would act on a prototype ring tail whose shape is different from those tested during this investigation.

ID: CaltechAUTHORS:20150529-141726043

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Abstract: At the request of the Naval Ordnance Test Station, Inyokern, Pasadena Annex, several tests were made at the Hydrodynamics Laboratory, California Institute of Technology, under contract NOrd 9612 to supplement the investigation being made at the Naval Ordnance Test Station (NOTS) under NOTS Task Assignment Re 3d-454-1-52. The NOTS study refers to air-launched missile shapes which oscillate in the cavity during the cavity phase of the underwater trajectory. The purpose of the study is to correlate the behavior of these missiles in terms of distance traveled between the contacts of the tail of the missile with the cavity wall. It is hoped that this parameter can ultimately be used to predict missile stability. In order to decrease the number of variables, the study was begun with only two nose shapes: the hemisphere and a subcalibre flat plate having the same drag coefficient as the hemisphere. The various tail sections used on the cylindrical body section were flared cones of half angles ranging between 0° and 22.50°. Five slenderness ratios from 5.5 to 9.5 were investigated. The slenderness ratio was varied by increasing the distance from the cg to the tail. The distance from the cg to the nose was held constant and the weight and moment of inertia were the same for all of the models. Since it is not possible to vary the air pressure in the open model tank at NOTS, it was desirable to make a few tests in the Controlled Atmosphere Launching Tank (CALT) at the Hydrodynamics Laboratory to see if the behavior of these missiles was altered by changing the air pressure (i.e. changing the cavitation number).

ID: CaltechAUTHORS:20150604-163618966

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Abstract: Cavitation tests were conducted in the High Speed Water Tunnel on a proposed projectile with control surfaces on the nose. These tests were carried out in cooperation with Dr. Dergarabedian of the Thompson Laboratory, Naval Ordnance Test Station. Qualitative tests of this type which included a photographic study of nose fin cavitation have proved valuable in indicating necessary modifications of the projectiles and in indicating the direction which further studies might take.

ID: CaltechAUTHORS:20150529-154259783

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Abstract: In the past most of the experimental work in the field of hydraulic machinery has been conducted on complete machines. Because of the mechanical difficulties involved, relatively little work has been done to determine the performance and behavior of the individual components. Roughly, a hydraulic machine may be considered to be composed of three parts; a stationary inlet or guide d e vice, a rotating component or impeller, and volute or stationary collecting device. With a view to obtaining component performances, much experimental work has been done in testing combinations of impellers in various volutes. Individual performance is then inferred from changes in over-all behavior. A separate study of the components permits a more ready understanding of the processes occurring and through simplification allows analysis to be undertaken. If the complete characteristics of the individual elements of the machine were then either known or predictable, design would become more straightforward. Since the impeller is responsible for energy input to the flow, it seems clear that it should be the item of first interest. It would be highly desirable to be able to predict the head developed and the distributions of pressure which occur by methods other than the empirical cut and try. However, a satisfactory theory embracing all of the effects of real fluids and the complex geometries found in practice is not yet available. For that reason the problem must be simplified as far as possible, retaining only the essentials. To this end the impeller is assumed to be two dimensional, that is, the flow is restricted to depend only on radial and angular coordinates. For analysis, it is further assumed to be inviscid, incompressible and irrotational so that the methods of potential theory may be employed. This approach is familiar in fluid mechanics and much success has been obtained with it. However, it should be noted at the outset that the limitations of potential theory for flows of the sort described above are as yet unknown. The line of thought followed in this work is not novel. It is to be found in References 1 to 3, to mention a few of the current efforts. However, in most of these works the configurations studied are such that analysis or comparison with a theory in any systematic way is difficult. The blade shape chosen for analysis is a logarithmic spiral. This shape is the only one that is mathematically convenient but, fortunately, most blades used in practice are closely represented by such shapes.

ID: CaltechAUTHORS:20150529-140358132

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Abstract: The measurement of model drag in the High Speed Water Tunnel has been difficult because of the interaction of pitching moment and the measured drag forces. Due to the mechanical arrangement of the force table used. pitching moment will produce reaction at the drag gage causing an erroneous reading. An internal balance has been fabricated which measures pitching moment. allowing a correction to be applied to the drag gage reading.

ID: CaltechAUTHORS:20150529-144332439

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Abstract: Resistance tests were conducted in the High Speed Water Tunnel on 2-in. diameter models of the 5-in. A. S. Projectile, Ex 30, and the 6-in. Projector Charge, Ex 1. The 5-in. A. S. Projectile was found to have a terminal sinking velocity of 39.4 fps with armed nose fuse and 35.7 fps for the flat nose projectile without fuse. The terminal sinking velocity for the 6-in. Projector Charge was 34.3 fps with armed nose fuse and 32.6 without the fuse.

ID: CaltechAUTHORS:20150506-101740603

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Abstract: With the help of a hypothesis first proposed by Mirkwood and Betbe, the partial differential equations for the flow of a compressible liquid surrounding a spherical bubble are reduced to a single total differential equation for the bubble-wall velocity. The Kirkwood-Bethe hypothesis represents an extrapolation of acoustic theory and would be expected to be most accurate when all liquid velocities are small compared to the velocity of sound in the liquid. However, the present theory is found to agree quite well with the only available numerical solution of the partial differential equations which extends up to a bubble-wall velocity of 2.2 times the sonic velocity. In the particular case of a bubble with constant (or zero) internal pressure, an analytic solution is obtained for the bubble-wall velocity which is valid over the entire velocity range for which the Mirkwood-Bethe hypothesis holds. In the more general situation, when the internal pressure is not constant, simple solutions are obtained only when the bubble-wall velocity is considerably less than sonic velocity. These approximate integral solutions are obtained by neglecting various powers of the ratio of wall velocity to sonic velocity. The zero-order approximation coincides with the equations for a bubble in an incompressible liquid derived by Rayleigh; the first-order approximation agrees with the solution obtained by Herring using a different method. The second-order approximation is presented here for the first time. The complete effects of surface tension, and the principal effects of viscosity, as long as the density variation in the liquid is not great, can be included in the analysis by suitably modifying the boundary conditions at the bubble wall. These effects are equivalent to a change in the internal bubble pressure. With this change, the same equations for the bubble-wall velocity are applicable to a viscous liquid with surface tension. Conditions under which the effects of surface tension and viscosity can be neglected are also determined. First and second-order approximations to the velocity and pressure fields throughout the liquid are derived. From these expressions, the acoustic energy radiated is calculated.

ID: CaltechAUTHORS:Gilmore_fr_26-4

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Abstract: Analysis or control of the trajectory of a cavity-running projectile requires knowledge of the hydrodynamic forces acting upon the vehicle. Although it would be desirable to describe these forces and moments completely for each proposed configuration, investigation of individual body components that might be combined as a complete projectile allows prior compilation of basic data that may aid in the most favorable combination of components for a variety of applications. Insight into the nature of the basic flow problems involved and the application of model data to problems involving a full-scale vehicle, will be aided by a piecewise study of the forces acting on basic geometric shapes.

ID: CaltechAUTHORS:20150603-113554244

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Abstract: This report summarizes experimental and analytical work conducted in the Laboratory during the first half of 1952. During this period the first task of the current change order, the preparation of a manual of harbor design, was also accomplished. Sections II and III of this report describe work done in connection with the second task assignment - the obtaining of further information concerning wave disturbances in harbors. The experimental part of this study was terminated for lack of time before positive results could be obtained. The study was nonetheless interesting and valuable since it pointed out the importance of further investigation of the stability of standing wave patterns in closed basins. Sections IV and V describe initial phases of two-and three-dimensional studies of scour, a program undertaken in accordance with the general provisions of the third task assignment of the change order. These studies are to be continued until the termination of the current contract period, and have been proposed for further study in the pending contract extension proposal.

ID: CaltechAUTHORS:20140624-155901196

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Abstract: A general objective of the Harbor Development study is the investigation of the wave energy distribution in harbor areas. Treated in a general way, the energy distribution in a harbor can be considered in two parts. The first concerns the amount and distribution of energy entering the harbor through the breakwater opening. Second is the consideration of the redistribution of energy by reflection and absorption at the harbor boundaries. The first part, that of diffraction through breakwater openings, has been presented by this Laboratory in previous progress reports(l). The second part, that of reflection and absorption at harbor boundaries, is the subject of this report. These factors are important in harbor design because the resultant wave pattern in a harbor is determined by both the incident and reflected waves. In any harbor with reflecting boundaries the resultant wave pattern is usually complex and an exact solution by graphical or mathematical treatment would prove very difficult. However, an approximate graphical solution, developed recently by this Laboratory, appears promising. This report presents the results of extensive measurements of wave disturbances in two idealized harbors and compares these results with those of the graphical analysis.

ID: CaltechAUTHORS:20140612-155415755

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Abstract: The Interim Report of October, 1951, presented a survey of the surface barrier studies which had been conducted by the Hydraulic Structures Laboratory up to that date. The performance curves of a number of types of mobile breakwaters were examined, and the decision reached that the most satisfactory one, all factors considered, was the three-bulkhead structure. After investigating the effect of such parameters as freeboard height, bottom clearance, and bulkhead spacing on the overall behavior of the barrier, a scale model of a hypothetical prototype pontoon assembly was constructed which incorporated what appeared to be the most effective values of these parameters. Performance data of this so-called optimum breakwater was given in the October report. The present report continues where the previous one left off, with a more intensive consideration of certain features of barrier performance which have been but vaguely understood. Specifically, the values of the coefficient of transmission, defined as the ratio of transmitted wave height to incident wave height, were determined under various controlled wave conditions for the following bodies: (1) Fixed single bulkheads of different bottom clearances. (2) Fixed three-bulkhead barrier. (3) Floating three-bulkhead barrier with fixed baffle extending upward from the bottom. (4) Floating barrier with weighted mooring lines. (5) Floating barrier with increased virtual mass on the end bulkheads. (6) Floating barrier with hydrofoil added forward of first bulkhead. In general, these conditions imposed upon the barrier were artificial, and impractical, as far as direct application to a prototype structure is concerned. Some information was gained, however, by separating to a limited degree the various factors which influence energy transmission by the floating breakwater. Unless specified otherwise, the floating barrier referred to in this report is the optimum structure with three bulkheads spaced at 73 and 127 feet, high freeboard, and 15-foot, 5-foot and 15-foot bottom clearances. The original performance curve of this body, obtained using soft springs in the mooring lines, is the second curve of Fig.8 in the October report, and is used frequently as a convenient basis of comparison for the data obtained in the present series of tests.

No.: 36
ID: CaltechAUTHORS:20140612-142422930

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Abstract: In studies made in the Free Surface Water Tunnel of a projectile running in an air-maintained cavity, the experimental relation between air entrainment rate and cavitation number was determined. The entrainment-rate coefficient CQ = Q/V0d^2, where Q is the air rate in cfs, V0 the free-stream velocity, and d the disk nose diameter, was plotted against cavitation parameter, K = (p0 - pk)/q0 where p0 is the free-stream pressure at the disk center line, pk the cavity pressure, and q0 the free-stream dynamic pressure. This experimental relationship for one single disc is shown for three different velocities in Fig. 1. The curves are similar in shape and each has a minimum value of entrainment coefficient which is designated by CQ^* at a value of K as designated as K^*.

ID: CaltechAUTHORS:HydroLabRptM-24.3

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Abstract: As a part of the program to study high sinking rate shapes, a series of drag tests was run in the High Speed Water Tunnel. Since flat noses are used to facilitate water entry, a preliminary investigation was made of the drag of flat nosed bodies of varying bluntness. The study as planned will later include streamline shapes. Drag measurements were also obtained for the 6-in. Projector Charge Ex. l and the 5-in. A. S. Projectile Ex. 30.

ID: CaltechAUTHORS:20150529-153908178

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Abstract: The effect of hydrojets on the drag characteristics of a two-dimensional hydrofoil was investigated in the High Speed Water Tunnel. The jets were found to affect drag through changes both in skin friction and pressure distribution, and when cavitating they showed some additional change.

ID: CaltechAUTHORS:20150604-152914960

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Abstract: An experimental investigation was made of the drag characteristics of a 2-in. diameter model of the standard (Head F) Mk 13-6 torpedo during the cavity phase of the underwater trajectory. The data used in this analysis were available from a previously completed trajectory study. These data were sufficient to determine the instantaneous velocity of the model along its trajectory. Hence, the deceleration and the instantaneous drag coefficient could be determined. The model was dynamically and geometrically similar to the prototype; its entry velocity of 120 fps was scaled from the prototype velocity of 406 fps in accordance with the Froude law. Results from model runs made at nominal atmospheric pressures of 1, 1/2, 1/11, and l/22 atmospheres with initial pitches between ± 6° are presented. A fixed trajectory angle of 19° was used in all tests. Prototype data from the Naval Ordnance Test Station, Morris Dam, taken at a nominal trajectory angle of 19° with initial pitches between ± 1° were available for comparison. Results from three tests of the Mk 13-6 torpedo model with the finer Dunn nose (Head I) made at air pressures of 1, 1/11, and l/22 atm. are also presented. These runs were made with a nominal trajectory angle of 20° and entry velocity of 120 fps with initial pitches between ± 0.5°. There were no prototype data from this shape suitable for drag analysis. The results of the investigation are summarized in the conclusions at the end of the report.

ID: CaltechAUTHORS:20150507-151328894

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Abstract: The following report considers certain aspects of the statistical problems presented by turbulence. Attention has been given in the first place to correlations as defining a structure in the field and to their importance in the phenomenon of diffusion. In attempting to describe the structure of the field by resolving it into simple components, we are faced with the coupling between the components as expressed by the nonlinear form of the hydrodynamic equations of motion. A number of basic effects of nonlinearity in a dissipative system can be studied with the aid of a simplified mathematical model. This model enables us to investigate various problems closely analogous to cases of turbulent fluid motion and presents similar questions referring to spectral resolution. Finally, some aspects of the current statistical theory of isotropic turbulence have been compared with results deduced from the model.

ID: CaltechAUTHORS:20180104-124827963

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Abstract: The wave and surge study, Contract NOy-13116, had as its ultimate objective the evaluation of the acceptable upper limits of water motion for different types of waterfront activities carried on in a modern harbor. Previous experience had made it clear that relc1lively little work had been done in this field and that few satisfactory instruments or techniques were available for the carrying out of such a program. Therefore, in order to obtain the objective, it seemed necessary first to decide what field measurements were pertinent; next to develop methods and instruments for obtaining the measurements, then to plan and carry out a measurement program, and finally, to analyze and evaluate the data obtained. Since the Los Angeles Harbor was a convenient location for the contractor, and since it is a major harbor with a wide scope of activities, it was chosen as the site for all of the field tests and measurements of the project. A secondary objective of this study grew out of the fact that a mole had been constructed recently to protect the area of the U. S. Naval Base within this harbor. This construction had been guided by a n extensive model study carried out at the California Institute of Technology. It was therefore fell desirable to ascertain, if possible, how nearly the protection afforded by this mole agreed with that predicted on the basis of the model study.

ID: CaltechAUTHORS:20140626-144026961

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Abstract: Characteristics of flows around curved sections of open channels at velocities greater than the wave velocity (that is, F > 1) are discussed in this paper. In simple curves such flows produce cross-wave disturbance patterns which also persist for long distances in the downstream tangent. These disturbance patterns indicate nonequilibrium conditions whose basic cause (when F > 1) is that disturbances cannot be propagated upstream or even directly across the channel. Thus, the turning effect of the curved walls does not act equally on all filaments in a given cross section and equilibrium is destroyed. The paper outlines two basic methods of eliminating these disturbance patterns. Analytical design criteria are developed, and experimental verifications of the analyses are presented. The first method consists of applying a lateral force in such a way that it acts simultaneously on all filaments, causing the flow to turn without disturbing the equilibrium. Bottom banking supplies such a lateral force, and a series of vertical curved vanes across the channel has roughly the same effect. The second method employs interference patterns introduced deliberately at the beginning and at the end of the curve. Compound curves, spiral transitions, and sills all operate on this principle. Rectangular channels are uniquely suited to the interference method of treatment, since for a given channel the wave patterns are substantially independent of the flow. Trapezoidal and other nonrectangular channels should be avoided if possible, unless the flow is invariant. The fields of application of the different treatments are discussed briefly.

No.: 99
ID: CaltechAUTHORS:20140905-102048694

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Abstract: This report presents the results of studies of the problems and possibilities of mobile breakwaters. The field of study was divided into two main parts: the general investigation of the hydromechanical laws pertaining to the problem of wave height attenuation, and the laboratory investigation of some specific devices which offered some promise of meeting minimum operational requirements.

ID: CaltechAUTHORS:20150629-144939390

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Abstract: This report describes work performed during the period from August 1, 1949 to November, 1950. When the project was started, it was financed for one year with the intention of continuing it for a second year, and the program was planned accordingly. However, after about three months of operation, it became necessary for reasons of economy to reconsider the original plans, with the result that the funds for the first year's operation were reduced and plans for continuing the work beyond the first year were dropped. In the early summer of 1950, the U. S. Air Force indicated its interest in sponsoring the work. In view of this prospect, the Office of Naval Research (ONR) allotted funds for an additional three-months' period to allow time for working out the necessary contractual arrangements with the Air Force for continuing the work. These arrangements were worked out and the studies were continued under contract with the Office of Air Research, starting November 1, 1950.

ID: CaltechAUTHORS:20150626-121127036

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Abstract: In many fluid flows of practical importance in engineering, agriculture, and meteorology, the presence in the flow of foreign matter which is transported by the flow is of great importance. Erosion by flood waters is one important example, the pollution of masses of water or atmosphere is another. The importance of the transported matter arises in various ways; in some cases principal interest centers on the quantity of an impurity removed by a flow, while in others a determination of the characteristics of the main flow itself depends to a large extent on the quantity and nature of solid matter entrained by the flow and carried along in it. The possibility of controlling or predicting such phenomena depends on a knowledge of the physical mechanisms of the processes which are involved. At the present time such knowledge is insufficient to cope with important practical problems. When the foreign matter consists of solid particles, as in problems of erosion and sedimentation, it is natural to seek an analogy with molecular processes by supposing that the history of each particle or group of particles is characterized by a randomness of the same type present in molecular kinetics. A diffusion theory is thereby obtained, the practical value of which is, of course, determined solely by its ability to explain observed phenomena. Under some circumstances both qualitative and quantitative agreement is found to be good; in other important cases the agreement is less than satisfactory. Similar analogies are used when one considers processes near boundaries at which foreign matter is entrained into and leaves the flow. One then draws analogy with the recognized theories of turbulent transfer of momentum, heat, and vorticity. These attempts likewise meet with varying degrees of success. Experiments in sedimentation (Vanoni, 1946) have shown not only limits of the theories which have so far been applied, but they have also indicated roughly the dependence of observed discrepancies on parameters in some cases where the analogy theories fail. These circumstances may facilitate attempts to obtain more refined theories. As a first step toward obtaining such refinements, the investigation described by the present report was conducted with a dual purpose : (1) to make an examination of the fundamental physical and mathematical features of classical molecular diffusion theory, with particular regard to the complications which are believed to be at the base of observed discrepancies in analogy theories and (2) to survey the work which has been done in allied fields, especially meteorology, in which similar problems have been faced for many years by competent physicists and mathematicians, in order to see which refinements may be carried over to the theory of sedimentation and turbulent diffusion and to suggest new lines of attack which may be fruitful. As the difficulties with the theory are largely due to great mathematical complications in any but the simplest problems, the discussion which follows places emphasis on mathematical techniques. In order to make the presentation more readable to workers in hydraulics who do not make frequent use of modern advanced techniques of mathematical physics, the discussion is confined to a moderately elementary level.

ID: CaltechAUTHORS:20150629-105950661

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Abstract: Investigation of the theoretical aspects of water-wave diffraction through an opening in a breakwater has progressed in two principal directions. First, the work of Penney and Price (1), in adapting Sommerfeld's solution of the optical diffraction problem to the case of water-wave diffraction, has been studied with a view toward generalizing it to suit any angle of wave incidence. In the second place, pursuing the method of a group at the Massachusetts Institute of Technology (2,3,4,5), an application of Mathieu functions to the case of water-wave diffraction has been made, to achieve an exact solution of the problem. This second phase of the investigation seems to be especially fruitful in that the total amount of energy entering a harbor, and the distribution of energy within the harbor, can be numerically computed. Tables of constants involved in this computation are being published by the National Bureau of Standards, and will be generally available soon. computation forms have been devised which permit routine calculation of the desired quantities by sub-professional personnel. Although the work of calculation has been reduced to a straightforward task, the amount of work which will be required for a complete set of energy distribution plots, covering a wide range of gap widths and wave directions, is so great that efforts are being made to have this computing performed by IBM machine at the National Bureau of Standards' Institute for Numerical Analysis.

ID: CaltechAUTHORS:20140625-155519024

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Abstract: The noise produced by the motion or a body through a liquid differs from that produced by the motion of a body through a gas because of the possibility or cavitation in the liquid case. An adequate theory or cavitation and cavitation noise is not yet available, but the application or dimensional analysis together with the theoretical information so far obtained can yield scaling laws for this flow situation. In section II, a brief dissussion will be given or the scaling laws for hydrodynamic noise in some cases of non-cavitating flow; this discussion is included tor oompleteness. In section III, a summary or the present information on the scaling law. for incipient cavitation noise will be presented.

ID: CaltechAUTHORS:20140626-153701552

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Abstract: This report summarizes the results of the first phase of the Laboratory's current comprehensive study of harbor design. This phase comprises the study of the transmission of wave energy through, and the distribution of wave energy behind, breakwater openings. The results obtained to date relate the effect of three major variables; width of breakwater opening, direction of wave approach, and breakwater alignment, on the two quantities mentioned above. The results of this study are subject to certain limitations, notably the small number of cases studied, the idealization of harbor and breakwater configuration, and experimental error. However, the results are considered to be far more quantitative than qualitative and to be of definite usefulness and value in harbor layout and design.

ID: CaltechAUTHORS:20140718-113129716

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Abstract: Two general physical processes by which wave energy may be excluded from a region are wave reflection and wave interference at the seaward boundary of the region. Wave reflection is the common basis of operation of conventional breakwaters, and for such structures is accompanied by the development of large forces and overturning moments. Wave interference is also a common occurrence although less generally understood, being responsible for the characteristic diffraction effects observed when waves pass through a breakwater gate. Because of the large forces developed, a mobile breakwater designed to totally reflect incident storm waves appears to be an impossibility, but there is a good possibility that submerged breakwaters, which are partially reflecting barriers, may be designed which will provide sufficient protection to be useful and subjected to forces small enough to permit installation and maintenance. In addition, if several such partially reflective barriers are installed in series, it may be possible to take advantage of waves interference to increase greatly their net effect. The Laboratory is presently engaged in a study of this system of mobile breakwaters. The factors to be investigated include: (1) Determination of reflection coefficients of a submerged barrier as a function of barrier height and wave length. (2) Determination of reflection coefficients of multiple barriers. (3) Determination of range of wave lengths effectively reduced for fixed barrier spacing. The determination of the forces exerted on the structures is not included in this investigation. This program is still in operation at the laboratory; this progress report presents preliminary data which will be augmented in the Final Report on the Mobile Breakwater Investigation, which is now in preparation.

ID: CaltechAUTHORS:20140612-143745789

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Abstract: Measurements were made of the drag forces acting on projectile noses rotating at zero yaw about an axis parallel to the direction of the approaching flow. The noses were rotating in the cavity formed at a cavitation number of about 0.29, based upon the approach velocity. Thus, only the front portion of the nose was in contact with the water.

ID: CaltechAUTHORS:20150630-100637764

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Abstract: This paper presents a theoretical and experimental method of selecting the optimum slenderness ratio of a body with cylindrical midsection. Whether such a body is a large submarine or its arch enemy, the depth charge, the problem rem a ins to find a slenderness ratio which will permit the fastest possible velocity consistent with the power or sinking weight available. Considerable research has been done to determine the hydrodynamic characteristics of nose shapes both alone and combined with various afterbodies. In one of our reports we have pointed out that any one of several different nose shapes could be used on a particular body with little change in the total drag coefficient, and tests for certain afterbody shapes would probably bring similar results. Due to practical considerations, most bodies have a cylindrical midsection. Therefore, a typical underwater body of axial symmetry consists of arbitrarily selected nose and afterbody shapes separated by a cylindrical midsection. For dynamic stability, any underwater body must have fins which increase the surface area and, to some degree, the residual drag. We must necessarily consider the effect of such fins on slenderness ratio. In the following discussion of a particular concrete example, the emphasis has been placed on a body with a nose and afterbody with fins, of the same geometrical shape as the MK 13-1 torpedo (less shroud ring). The MK 13-1 torpedo is dynamically stable, has a cylindrical midsection, and has been tested with other nose shapes. After examination of the factors affecting the optimum slenderness ratio, it is found that a reasonably large variation from the theoretical optimum value will have little practical effect on the velocity of the body. Because of practical factors involved in the design of an undersea body, it may be desirable from the designer's point of view to have a relatively large slenderness ratio. This investigation shows that as far as drag per unit volume is concerned, the designer will will pay very little, if any, penalty if he disregards the drag factor and bases his selection of slenderness ratio entirely on such items as tactical requirements of maneuverability, structural design and utilization of internal space.

ID: CaltechAUTHORS:20150630-101551822

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Abstract: It has been known for some time that an analogy exists between the flow of a liquid with a free surface and the flow of a compressible gas. A less accurate analogy has been shown to obtain between hydraulic jumps and compression shocks. The interaction of shocks can occur in two forms; the regular or two-shock configuration and the Mach or three-shock configuration. The latter configuration is not yet completely understood, either in the case of hydraulic jumps in a free-surface liquid or in the case of shocks in a compressible gas. This experimental study was primarily concerned with the Mach interactions of hydraulic jumps. The conclusions of this study are: (a) there is a definite disagreement between experiment and existing theory; (b) a depth discontinuity, or wave, rather than a velocity discontinuity separates the region behind the Mach wave from the region behind the reflected wave; (c) there is evidence that, for interactions of weak hydraulic jumps, there is a deviation from constant depth between waves; (d) the Mach wave is convex for the interaction of the stronger hydraulic jumps, but is concave for the interaction of weak hydraulic jumps; (e) measurements should not be made so as to allow for curvature of the Mach without considering the curvature of the incident and reflected waves in the neighborhood of the triple point.

ID: CaltechAUTHORS:20150529-110331320

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Abstract: From the results of tests conducted in the Hydraulic Machinery Laboratory at the California Institute of Technology, the pump performance was analyzed and found to be satisfactory for the pumpjet installation in the Mark 40 Torpedo. The pump will operate at or very near the point of best efficiency, which is 84.5 ± 1.0 per cent at a projectile speed of 80 knots. The propulsion unit was tested from zero flow rate point through zero head point into the reverse turbine range. The performance was found to be very similar to that of a conventional centrifugal pump fitted with a diffuser vane case or a volute case.

ID: CaltechAUTHORS:20150629-155155576

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Abstract: This paper considers one aspect of the effectiveness of a single or repeated air bubble screen as a breakwater for gravitational waves in shallow water. The aspect considered arises from the change in density and compressibility of the bubbly water as compared with normal water outside the screen. The effects of currents produced by the mass of rising bubbles will be discussed elsewhere. use is made here of the notation and some results from another paper entitled 'Gravitational Waves in a Shallow Compressible Liquid;' equations from that paper are denoted by primes. The properties of bubbly water are considered first, then the transmission of waves through a single bubble screen, and finally the transmission through a series of equally spaced screens.

ID: CaltechAUTHORS:20150629-110810200

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Abstract: Free-surface water tunnels are used to determine the hydrodynamic characteristics of bodies which move in water near the surface. To develop the basic principles for the design and operation of such a tunnel the conditions for dynamic similitude near an air-water interface are analyzed. Although the tests should determine how the hydrodynamic characteristics are affected by the surface waves produced by the body itself, the dimensions and conditions of operation of the test channel are sometimes responsible for disturbances that interfere with the interpretation of the local wave effect. In order to record the type of interfering waves that might be expected and the conditions responsible for their occurrence, the Free-Surface Water Tunnel at the Hydrodynamics Laboratory of the California Institute of Technology was temporarily operated under these conditions. Since the local wave pattern produced by the body under study depends primarily on the criterion for inertial-to-gavitational similitude between model tests and prototype operation, the relation between this criterion and the conditions that produce the undesirable channel waves is discussed. Application of gravitational similitude usually results in model tests that are different from prototype operation in respect to viscous and surface-tension effects. A chart is developed showing the relations for gravitational similitude and indicating the resulting dissimilitude for viscous and surface-tension phenomena. This chart is also used to indicate the complete range of operation of a free-surface test channel as well as the range in which undesirable waves are produced in the working section. Through recognition of the nature of the interactions between the hydrodynamic characteristics of the tunnel and the body under investigation, design and operation principles for a free-surface water tunnel are developed showing how to decrease or avoid the wave difficulties and minimize the unavoidable dissimilitude.

ID: CaltechAUTHORS:20151015-153609683

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Abstract: The subject matter covered in this report concerns the characteristics of the surface waves produced in the ripple tank by the wave generators and the effect on the wave form of adding detergents to the working fluid. The results will be presented under the following headings: 1. Experimental procedure. 2. The wave generators. 3. Variables affecting wave strength. 4. Effect of adding detergents to working fluid. 5. Summary and conclusions.

ID: CaltechAUTHORS:20140603-151624030

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Abstract: Water entry tests of 2-inch diameter models of the MK 13-6 Torpedo with two nose shapes were made in the Controlled Atmosphere Launching Tank to determine: a. The effect of atmospheric pressure on the water entry behavior of small models. b. The influence of nose shape on the magnitude of atmospheric pressure effects. c. Whether model behavior will be similar to prototype behavior when the speed is scaled according to the Froude law and atmospheric pressure according to the linear scale, and atmospheric density is allowed to vary with the pressure.

ID: CaltechAUTHORS:20150722-151028818

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Abstract: The general objective of the Harbor Development Study is the investigation of the wave energy distribution in simple harbor areas, with the specific objective of determining design principles which will permit the prediction of harbor performance. The progress accomplished to date has consisted of the analysis of the problem in terms of applicable physical principles, the review of present knowledge or these principles, the formulation of a general laboratory program, and the construction of the laboratory facilities required for the first phase of the program. This report considers each of these items in turn.

ID: CaltechAUTHORS:20140723-141450682

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Abstract: This report covers further work on the refraction of waves by opposing currents, and is essentially an elaboration of earlier results. Two types of currents have been considered, a horizontal flow of substantially constant velocity from surface to bottom, and a horizontally stratified flow characterized by high velocities near the surface and relatively low velocities in the opposite direction across the rest of the vertical section. For the first type of current, a revised theoretical treatment is presented, together with experimental results which are in good agreement with the theory. For the second type of current, experimental results have been obtained for a range of current intensities much higher than would be practical in a prototype installation. The results of these experiments do not change the earlier conclusion that the refraction of waves by opposing currents, and hence the pneumatic breakwater, is not a practical means for materially reducing wave disturbances. These experiments do extend the experimental investigation to cover the complete range of wave types, from deep-water to shallow-water and of current values to well over any conceivable prototype range.

ID: CaltechAUTHORS:20140725-114954873

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Abstract: Activities during the month were centered principally around the continuation of studies initiated in July and August and upon analysis of data collected for the studies. Refraction diagrams are being drawn as a part of the frequency response study and will be used as an aid in the determination of the mode of oscillation of the basin. The pollution study received the most attention during the month. A channel has been constructed in the model across Orote Peninsula between the south end of the inner harbor and Agat Bay. This channel is being used in studying the circulation possibilities in the inner harbor and repair basin under normal ocean conditions. The wave height averaging device is now completed and calibration and testing of the circuits are progressing rapidly.

ID: CaltechAUTHORS:20140701-150245327

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Abstract: The cavity phase of the water entry of a projectile is described and the results are presented for the beginning of an experimental investigation of the hydrodynamic forces that affect projectile motion within a cavity. Lift-force measurements were made on two afterbody shapes that were supported so that they dug into the surface of a flowing stream of water. The similarity between these tests of models in the Free-Surface Water Tunnel and operating conditions of a full-scale projectile is discussed.

ID: CaltechAUTHORS:20140623-151752095

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Abstract: The inherent difficulties in obtaining the solution for the flow about arbitrary bodies of revolution near a wall usually precludes on exact evaluation of the effect of wall proximity on the pressure distributions However, many bodies of revolution may be replaced with good approximation by an ovary ellipsoid. For this purpose, an approximate solution for the velocity potential is obtained for the flow about an ellipsoid near a plane wall which approaches the exact solution in an infinite stream as the ellipsoid recedes from the wall. The evaluation of the image potentials and rectifying images is accomplished by an expansion in associated Legendre polynomials. A first approximation, which results in a symmetric distribution on the ellipsoid, is essentially an expansion in associated Legendre polynomials of zero order. A second approximation, which correctly predicts differences of pressure on opposite sides of the ellipsoid, is carried out by an exact evaluation of the effects of the image potentials while evaluating the rectifying images by the same method as followed for the first approximation. The solutions ore obtained in closed form with resulting expressions for the velocity and pressure distributions that are especially convenient for application to specific cases. The solutions are compared with pressure distributions measured on two ellipsoid models placed near a plate, simulating a wall, in the free surface flume of the Hydrodynamics Laboratory. The first approximation shows good agreement along the meridian parallel to the wall but rather large deviations at other points of the ellipsoids. This approximation is probably most useful only for estimates of the change in pressure distribution for varying separations; and where a high degree of precision in actual values is not required. The second approximation, on the other hand, shows very good agreement for distances even as small as one diameter from the center of the ellipsoid to the wall. For smaller distances this approximation shows large point of the half meridian accuracy for points on the wall.

ID: CaltechAUTHORS:20150625-164256043

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Abstract: Studies of induced currents were the main activity of the month. Preliminary frequency response studies were started and detailed marigram analysis was resumed. Studies of induced currents involved development of methods, running of tests and analysis of data. Some currents are induced in the harbor by the waves which pass through the entrance. These were the currents studied. They give basic data. Tidal changes and outer ocean currents will be superposed later to learn of composite effects. Frequency response studies were initiated this month also. The present wave machines were designed to make such tests possible, since both amplitude and frequency of the wave trains can be controlled over wide ranges. It is intended to run tests through the entire spectrum after observing and measuring the effects of certain calculated frequencies. The calculated frequencies were the fundamentals and harmonics of each division of the harbor. Marigram analysis was resumed along the lines of the program previously decided upon, i.e. computation and plotting of residual mass curves between adjacent stations. These curves reveal the duration and rate of flow which could obtain through the proposed pollution channels. Modification to the oscillograph was made to reduce the tape speed, the range in speeds being broadened accordingly. Component parts of the wave height averaging device are being assembled as received.

ID: CaltechAUTHORS:20140724-164430697

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Abstract: Tests of three different inner breakwaters to protect the repair basin and inner harbor from waves entering through the existing harbor entrance were run this month. Two were located on Jade and Southern Shoals and one on Jade, Southern and Western Shoals. The breakwaters on the shoals reduce the disturbances in the areas of primary and secondary usage in the repair basin to less than half those occurring with the shoals alone. Combinations of breakwaters and channel fills between the various shoals supplemented the studies and these results are included as well. Tests were also run to compare the effectiveness in the outer harbor of the alternate entrance through Luminao Reef with that of the existing entrance between Spanish Rocks and Orote Point. The alternate entrance is very effective. In addition to the tests described above, induced current studies were made. Many of these were for the purpose of developing the technique of daytime photography of reflector floats. Because test runs at the end of the month are incomplete and do not comprise a logical unit for presentation, their analysis will appear in next month's report.

ID: CaltechAUTHORS:20140723-094808025

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Abstract: The data presented in the February report were analyzed further during the month of March. This analysis, guided by BuDock's letter of 4 December 1947, BuDock's dispatch of March 1948, and a conference with the OinCC of the contract, resulted in comparisons of shoal effects on the basis or averaging the disturbances in the repair basin areas designated for primary use. This average facilitates the comparison of the effectiveness of the different protective structures, since each average characterizes the performance or each given structural configuration under a given imposed ocean condition. Experimentation was started on photography to record induced current movements within the harbor. Attempts are being made to adapt the equipment available to the taking of pictures in the daytime rather than during the late evening and early morning hours found necessary for the Pasadena model. The wave height measuring unit which gave a great deal of trouble in the latter part of February was thoroughly reconditioned during the analysis period to reduce delays which might otherwise arise during the running of future tests.

ID: CaltechAUTHORS:20140724-152559092

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Abstract: Flight tests of the XBT2D-1 Airplane with 2,000 pound G. P. Bomb externally attached to the fuselage resulted in serious buffeting at critical air speeds. In a memorandum from the Bureau of Ordnance, U. S. Navy, dated 13 May, 1946, the Hydrodynamics Laboratory at the California Institute of Technology was requested to make Polarized Light Flume studies and cavitation tests on a model. The object of the tests was, originally, to obtain information helpful in eliminating such buffeting.

ID: CaltechAUTHORS:20151020-154229096

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Abstract: This laboratory was requested to recommend a nose design for the 12.75-inch Antisubmarine Rocket which would give a terminal velocity of 40 feet per second. Such a nose was to have a flat face with a diameter not less than half the projectile diameter. Two designs are submitted herein. The diagram shows their outlines together with that of the original nose. Calculations indicate that either should give a terminal velocity between 47 and 48 feet per second in sea water of 60° Fahrenheit (with 23.7 lbs. of water in discharged motor tube, 45 ft/sec if empty). These nose shapes are sufficiently different to afford considerable latitude in respect to characteristics of maximum range, ricochet, cavitation, and performance in the entry bubble. It is unlikely that any other nose shape could further materially reduce the drag while other components remain unchanged. The new noses have trivial effect on the cross force coefficient developed with the original nose and all have considerable static stability.

ID: CaltechAUTHORS:20150723-173714304

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Abstract: Reported herein are tests of the 500 pound T 16 S. P. Bomb covering the hydrodynamic force coefficients with and without cavitation, incipient cavitation characteristics, and flow lines as revealed in the Polarized Light Flume. It was not possible to cause full cavitation with present water tunnel limitations.

ID: CaltechAUTHORS:20151020-163119249

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ID: CaltechAUTHORS:20140701-155709448

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Abstract: Reported herein are tests of the 7.2-inch Antisubmarine Rocket with eight different noses. The purpose was to determine the hydrodynamic force coefficients without cavitation and in a full bubble, incipient cavitation characteristics, and flow conditions as revealed in the Polarized Light Flume.

ID: CaltechAUTHORS:20150630-104642522

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Abstract: Contract OEMsr-207 has been a project operated under Section 6.1 of the National Defense Research Committee. It has been under the general supervision of Dr. John T. Tate, Chief of Division 6, and the detailed supervision of Dr. E. H. Colpitts, Chief of Section 6.i. Under this contract, studies have been carried out under Navy Projects NO-i4iJ NO-i76J NO-i49 and NO-i57J and Army Projects OD-99 and AC-70. In addition, studies have been made directly for Contract OEMsr-4i8 operating under Division 3 of the National Defense Research Committee, Columbia University, Division of War Research, operating under Division 6, and for other projects as authorized by Division 6. Nearly all of the projects studied have involved the determination of the hydrodynamic forces acting upon projectiles in flight, either in the air or under water. The initiating problem was the study of the streamlined depth charge for the New London Laboratory. Subsequent projects broadened the field of the Laboratory work to include rockets, bombs, mortars, shells, and torpedoes. The purpose of this report is to present a brief review of the work carried out by the California Institute of Technology under Contract OEMsr-207 for Section 6.1 of the National Defense Research Committee. This summary includes a review of the types of problems assigned to the project, a description of the equipment developed to make the measurements required for the solution of these problems, a brief resume of the work that was completed by the projects, and a short survey of the present state of the field, including the problems that deserve further study.

ID: CaltechAUTHORS:20140723-143216577

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Abstract: The Mark 26 Tropedo is an underwater torpedo, electrically driven, 21.035 inches maximum diameter, and 245.875 inches long over-all. This report covers the results of tests made in the Hydrodynamics Laboratory of the California Institute of Technology on scale models of the Mark 26 Torpedo with four different designs of stabilizing fins. Tests in the High Speed Water Tunnel were made to determine the hydrodynamic forces under steady state conditions and to observe the pressure and velocity at which cavitation occurs. No tests were made to determine the damping forces. The tests were authorized by Dr. E. H. Colpitts, Chief of Section 6.1, National Defense Research Committee, in a letter dated October 8, 1943.

ID: CaltechAUTHORS:20150721-152444702

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Abstract: This report covers measurements of the pressure distribution around the body of the Mk 25 Torpedo equipped with a shroud ring tail) and includes studies of the effect on the pressure distribution of variations in yaw and pitch angles, velocity, and static pressure (i. e., submergence) The tests were made on a 2-inch diameter model (model scale 1 to 11.2). In addition to providing a general picture of the pressure distribution as affected by the different variables) the data presented herein are useful in determining the best locations and arrangements for the pressure intakes to the immersion mechanism and to the depth and roll recorder) and also as a check on cavitation measurements. Because the pressures on the fins themselves were not measured in these tests, the data cannot be used to calculate overall forces acting on the complete torpedo.

ID: CaltechAUTHORS:20151015-164322990

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Abstract: This report covers Water Tunnel tests made on a 2-inch diameter model of the Mk 53 Aircraft Depth Bomb. These tests were conducted at the Hydrodynamics Laboratory of the California Institute of Technology and were authorized by Dr. L. G. Straub, Head Technical Aide. to Section 6.1, National Defense Research Committee, in a letter dated July 12, 1945. This work included cavitation photographs of the model in the Water Tunnel under a wide range of values for the cavitation parameter, tests to determine the moment, drag, and cross force coefficients, and also tests to obtain the pressure distribution along the afterbody and the hydrostatic fuze located within the tail structure. The model was also provided with pressure taps at the nose and forward part of the body, but the pressure distribution for these taps was not determined on account of lack of time.

ID: CaltechAUTHORS:20150720-155152479

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Abstract: Force and cavitation tests of the United Shoe Machinery Corporation Hydrobomb, Design No. 8, are reported herein. There were two basic models, one having 28-inch fin span for both horizontal and vertical fins , and one with 28-inch vertical and 34-inch horizontal fin span. Seven models were actually tested, namely, one finless , 23-inch and 34-inch fin spans without rings, 28-inch and 34-inch fin spans with 10-degree cone angle rings, and 28-inch and 34-inch fin spans with 5-degree cone angle rings.

ID: CaltechAUTHORS:20151015-154629389

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Abstract: This report covers tests of a 2-inch diameter model of the 5" HVAR Projectile, conducted at the Hydrodynamics Laboratory of the California Institute of Technology. This work was authorized by a letter dated January 31, 1944 from Dr. E. H. Colpitts, Chief of Section 6.1, Office of Scientific Research and Development. The purpose of the tests was to determine the performance of the projectile with the standard 4-fin tail, and to investigate possible changes in the proportion of the fins in order to better the performance or make a more compact design. This report also includes an extensive investigation of the performance of various fin and ring tails applied to this projectile, as well as to similar projectiles of different lengths. It is hoped that the data contained herein may be of use in the design of a variety of bullet-shaped projectiles having either ring or fin tails. The Water Tunnel tests apply only to the projectile moving at subsonic speeds, i.e., during the acceleration period. The attached appendix gives definitions of the terms used throughout the text, as well as other pertinent data.

ID: CaltechAUTHORS:20150721-135934006

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Abstract: This report covers model tests in the High Speed Water Tunnel and Polarized Light Flume of the Hydrodynamics Laboratory at the California Institute of Technology on the following aircraft bombs for use against land targets and surface targets on water Concrete Practice Bombs (a) with large fin box tail, (b) with small fin box tail (c) with drum type tail M38A2 Practice Bomb AN-M43 G.P. 500 lb. Bomb AN-M56 L.C. 4000 lb. Bomb The tests were authorized under Project OD 99. Tests were made on two-inch diameter models in the High Speed Water Tunnel to determine the hydrodynamic forces (drag, cross force, and moment) under steady state conditions. No tests were made to determine the damping forces The test results apply only to velocities below the velocity of sound. Tests were made 1n the Polarized Light Flume to give a visual indication of the streamline patterns in steady flight. A comparison is made of the results of the Water Tunnel tests with tests previously made on models of the same bombs at the Wright Field Wind Tunnel.

ID: CaltechAUTHORS:20150721-133121995

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Abstract: This report covers measurements of the pressure distribution around the bodies of the Mk-1.4-1 and Mk 15-1 Torpedoes, both when equipped with the standard tail assembly and with a shroud ring tail added, and includes studies of the effect on the pressure distribution of variations in yaw and pitch angles, velocity, and static pressure (i.e., submergence). These two torpedoes are both 21 inches in diameter, made up with heads and afterbodies having the same external shape, and both are equipped with identical fin and rudder assemblies. The only difference between their external shapes, therefore is due to the different lengths of cylindrical mid-sections, and resultant different over-all lengths. (The Mk 1.4-1 is 20.5 ft long, and the Mk 1.5-1 is 24 ft long). The tests were made on 2-inch diameter models (model scale 1:10.5). In addition to providing a general picture of the pressure distribution as affected by the different variables the data presented herein are useful in determining the best locations and arrangements for the pressure intakes to the immersion mechanism and to the depth and roll recorder, and also as a check on cavitation measurements. Because the pressures on the fins themselves were not measured in these tests, the data cannot be used to calculate the over-all forces acting on the complete torpedo The main observations and conclusions are summarized in the following paragraphs: 1. Within the range of these tests the pressure, distribution, as presented in terms of p/q was found to be independent of variations in velocity and static pressure or submergence. That is, the difference between the pressure at any station on the body and the static pressure of the undisturbed water is independent of the static pressure and is directly proportional to the velocity head. 2. The addition of the shroud ring around the fins of these torpedoes has no measurable effect on the pressure distribution. 3. The pressure distributions around the head and afterbody of the Mk 1.5 i-1 ere found to be practically identical with those of the Mk 14-1. That is, increasing the length of the cylindrical mid-section does not, in this case affect the pressure distribution on the head or afterbody. 4. The pressure on the surface of these torpedoes equals the static pressure of the undisturbed water at two positions, one on the projectile nose and one on the afterbody (See Figures 12, 18, 24, and 30). Ahead and behind these two stations the pressure is above static, while between the two (which includes about 83% of the over-all length of the Mk 14-1, and 86% on the Mk 15-1) the pressure is below static. 5. The position on the afterbody at which P = P_0 is only slightly affected by yaw or pitch angles up to 3°. 6. On the basis of these measurements, made without rotating propellers, it appears that the best arrangement for the pressure intake to the immersion mechanism would be through a piezometer ring connecting to four pressure taps uniformly distributed about the circumference of the afterbody and about 35 inches ahead of the end of the tail. The pressure imposed on the diaphragm would then be equal to true hydrostatic pressure, and practically independent of yaw or pitch The influence of the propellers may shift this point slightly either aft or forward. 7. Placing the pressure take-off for the depth and roll recorder where P = P_0 on the nose is not recommended because P changes rapidly in this zone and large errors can result from small inaccuracies in locating the connection Connection of the depth and roll recorder to the point of the afterbody where P = P_0 is, of course, physically impracticable. It is recommended, therefore, that the pressure intake be left unchanged and, if necessary, determine the corrections to be applied to the depth record.

ID: CaltechAUTHORS:20150629-164245516

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Abstract: Various modifications of the external shape, but not of overall length or diameter, of the British squid, Type "C" Projectile were tested to determine an acceptable shape having materially reduced drag and no other characteristics which would be objectionable. The best modification obtained was the simple substitution of a special nose, previously designed by Mr. A. L. Kitselman, who was then employed by the Hydrodynamics Laboratory. The contour of this special nose was determined by the formula (X/1.5)^3 + Y^2 = 1. This model appears, by extrapolation, to have a drag coefficient of about 0.106 at R = 15 x 10^6 which would correspond to a terminal velocity of about 53.6 ft/sec. Calculations indicate that this might be raised to 55.0 by using four (strengthened) vanes in the tail instead of eight. The cross force coefficient is about 10% less than that of the production model, and the stabilizing moment coefficient about 11-1/2% greater. It is believed a bourrelet could be provided without materially affecting the hydrodynamic characteristics. The tendency to cavitate with this nose is somewhat reduced but its effect on performance during the bubble stage is not known at present, or even that it may be adverse. If so, it is probable that it could be within acceptable limits.

ID: CaltechAUTHORS:20150717-165131013

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Abstract: This report covers tests made on a 2-inch diameter model of the 5" spin-stabilized rocket. The tests were conducted at the Hydrodynamics Laboratory of the California Institute of Technology, and were authorized by a letter of January 31, 1944 from Dr E. H. Colpitts, Chief of Section 6.1, National Defense Research Committee. The purpose of the tests was to determine the performance of the rocket with various nose shapes and variations in body dimensions. Four different models were tested, the same afterbody being used in all cases. The attached appendix gives definitions of the terms used in this report, as well as other pertinent data. This report deals only with the static stability of the projectile without rotation. Since it is not possible to operate the water tunnel at velocities equivalent to supersonic velocities in air, the data herein are applicable to the projectile in the first stages of flight only.

ID: CaltechAUTHORS:20150721-134012008

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Abstract: [no abstract]

ID: CaltechAUTHORS:20151015-163314459

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Abstract: This report covers Water Tunnel tests of a 2" diameter scale model of the Westinghouse Hydrobomb. The results apply only to underwater performance under steady state conditions. No tests were made to determine damping characteristics. The tests reported herein were authorized by a letter dated January 29, 1944, from Dr. E. H. Colpitts, Chief of Section 6.1, National Defense Research Committee.

ID: CaltechAUTHORS:20150721-142904643

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Abstract: The purpose of the tests reported herein was to determine the effect upon hydrodynamic characteristics of two suspension bands of the same design when placed on the Mk 13-1 Torpedo with band centers spaced 14 and 30 inches and symmetrical about the center of gravity. Particular interest was in the effect upon torpedo running speed. The tests indicated that the bands would cause a reduction of approximately 2 knots from the normal speed of 33 knots. Cavitation measurements indicated that both of the top and bottom protrusions would cavitate at normal running speeds and depths. The effect of the bands on moment, lift, and cross force coefficients is, generally, of a minor nature.

ID: CaltechAUTHORS:20150721-160514639

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Abstract: This report covers the tests of a 2" diameter model of the 4. 5" H. E. Rocket, T38E3, to determine the force and moment coefficients and the location of the center of pressure. The tests were made in the 14" diameter working section of the High Speed Water Tunnel at the California Institute of Technology. The work was authorized by a letter of January 31, 1944, from Dr. E. H. Colpitts, Chief of Section 6.1, National Defense Research Committee, New York City.

ID: CaltechAUTHORS:20150721-141518044

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Abstract: This report covers tests made on models of the Mk 25 Torpedo to determine the effect of gas discharged in the vicinity of a power-driven propeller. It also covers, briefly, tests made on a double exhaust pipe and a single exhaust pipe, both with the vertical rudder set at 10° port but without propeller. All of the above was authorized by Dr E. H. Colpitts, Chief of Section 6.1, NDRC, in a letter dated May 4, 1944. This report is the fourth supplement to the report, Section No. 6.1-sr207-1275. Memorandum Reports dated June 22, 1944, July 15, 1944, and September 29, 1944 have been issued giving preliminary results on the tests reported herein. Tests were made on models having a scale ratio of 11:21. However, all dimensions and data refer to the prototype unless otherwise noted. Gas discharges are expressed in per cent. These figures have been calculated with reference to the amount of gas discharged from the prototype when running at 40.5 knots. Allowances for temperature and composition of the exhaust gases have been made by calculating the exit velocity when the torpedo is running at 40.5 knots and 15 feet submergence, computing the ratio of this velocity to that of the torpedo, and then calculating the amount of air required by the model to obtain this velocity ratio when operating at the equivalent submergence. This criterion requires that a different rate of air flow be taken as the 100% amount for each torpedo velocity investigated. However, as in the prototype the mass rate of gas flow in the model is constant for any given water velocity, independent of the changes in the tunnel pressure (i.e. submergence). With this torpedo operating at the normal speed of 40.5 knots and a submergence of 15 feet, the cavitation parameter is calculated to be 0.67. The appendix to this report gives definitions of terms and other pertinent data.

ID: CaltechAUTHORS:20151016-094648360

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Abstract: The High Speed Water Tunnel is operated by the California Institute of Technology under Contract OEMsr-207 with the OSRD and is sponsored by Division 6, Section 6.1 of the NDRC. The tests reported in this memorandum were made at the request of the U. S. Navy Department, Bureau of Ordnance as a part of Navy Project ND-141. The report covers water tunnel tests of a 2" diameter model of the 15" AN-MIC. 41 Bomb (Model Scale Ratio 7.5 to 1), and several modifications of this bomb. The hydrodynamic forces, the drag, crosswind force, and the moment, acting on the projectiles were measured and the locations of the center-of-pressure were calculated for various velocities and yaw angles.

ID: CaltechAUTHORS:20151014-105644593

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Abstract: This report describes measurements of high frequency noise produced by projectiles cavitating in a high velocity stream of water. Spherical and ellipsoidal focusing reflectors were used in conjunction with a Brush CC-11A hydrophone to locate the noise source.

ID: CaltechAUTHORS:20151014-170726215

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Abstract: This report covers model tests of the MK 13-1 Torpedo without shroud ring tail, conducted at the Hydraulic Machinery Laboratory of the California Institute of Technology. These tests were made at the request of Dr. E . H. Colpitts, Chief of Section 6.1, National Defense Research Committee, in a letter dated October 8, 1943, and were for the purpose of determining the performance of the torpedo with seven different types of nose design.

ID: CaltechAUTHORS:20150720-154152692

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Abstract: This report covers the progress made to date on an investigation of cavitation on various projectile nose shapes. It is closely allied with and supplements the report by Dr. R. T. Knapp, entitled "Entrance and Cavitation Bubbles " No 6.1-sr207-i900, dated December 27, 1944. All work reported herein was conducted at the Hydraulic Machinery Laboratory of the California Institute of Technology and was authorized by a letter dated January 17, 1944 from Dr. E. H. Colpitts, Chief of Section 61, National Defense Research Committee. As this investigation has developed, it is apparent that a very extensive series of tests will have to be made in order to cover the ground in a satisfactory manner. It was, therefore, thought best to prepare this progress report without further delay so that the results so far obtained might be made available. Other progress reports will be issued from time to time as additional tests are completed. In this report only the tests of ogive and spherogive noses will be described. A total of about 50 models of these two types of nose shape have been tested, and, it is believed some interesting and valuable information has been obtained. However, all data in this report must be considered as preliminary only and subject to corrections based on future tests. The work so far done has furnished a fairly comprehensive overall picture of the performance of these two types of nose even though the test data are rather meager. In order to obtain consistent results it has been found necessary to make the models to very close tolerances. All linear dimensions are held within + or - 0.001". Especial care is exercised to be certain that the curves forming the nose are truly tangent and match within 0.0001" or less. The angle of the spherical segment forming the tip of a spherogive nose must be held to within a quarter of a degree as in some cases a variation of 1° will cause a change of 15% in the value of the cavitation parameter.

ID: CaltechAUTHORS:20150701-142221201

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Abstract: This report is a supplement to a previous report of this laboratory entitled "Pressure distribution. Measurements on the MK 13-1, 13-2. and 13-2A Torpedoes", file marked Section No 6.1-sr207-1643, and dated June 23, 1944. It is a part of the program of investigation requested and authorized by Dr. E. H. Colpitts, Chief of Section 6.1 of the National Defense Research Committee, in a letter dated October 8 1943. The preceding report, referred to hereafter as Report 1643, included measurements of the pressure distribution about the bare hull and about the hull with fins but without shroud ring tail. The tests reported herein cover pressure distribution measurements on the torpedo with fins and shroud ring tail. The main objective of these investigations was to determine whether or not the depth control mechanism is actuated by true hydrostatic pressure.This is of interest because the immersion mechanism can keep the torpedo at set depth only if it is actuated by true hydrostatic pressure of the water at the running depth, and if this pressure is unaffected by variations in speed and in yaw or pitch angles.

ID: CaltechAUTHORS:20150722-141905237

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Abstract: The purpose of this report is to correlate the subject matter of Memorandum Reports M-24 and M-24.1. The purpose of the Memorandum Report M-24 December 8, 1944 was to obtain the drag coefficients for the model with a correctly proportioned tail. The purpose of Memorandum Report M-24.1, December 11, 1944, was to determine the drag coefficients of a true model of the current production type, with a new nose, at high K values, that is, at high pressures.

ID: CaltechAUTHORS:20150717-170111076

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Abstract: This report is a supplement to Report Section No. 6.1-sr207-1270, dated April 21, 1944, and coves tests conducted at the High Speed Water Tunnel at the California Institute of Technology. This work was authorized by a letter of January 31, 1944, from Dr. E. H. Colpitts, Chief of Section 6.1, National Defense Research Committee, New York City. The purpose of these tests was to determine the effect, on performance, of several different types of afterbodies. The first tests of this rocket showed that there was a slight stabilizing moment at very small yaw angles. this stabilizing moment had an undesirable effect on performance, and it was hoped that minor changes in the afterbody might overcome this difficulty. The Appendix gives definitions of the terms used in this report, as well as a brief discussion of the required conditions for stability in a nonrotating projectile. This report deals on with static stability of a projectile without rotation.

ID: CaltechAUTHORS:20151020-164727996

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Abstract: The purpose of this memorandum is to present a general discussion of the physical nature of two phenomena : (a) cavitation on underwater projectiles, and (b) the enveloping bubble formed when a projectile enters the water at moderate or high velocities. In this discussion an effort is made to demonstrate a close relationship between the two phenomena. In attempting to explain their various aspects, several hypotheses are advanced concerning the physical mechanisms involved. Although these hypotheses are founded on laboratory measurements and observations, the experimental work is far from complete. Therefore, the explanations and conclusions contained herein are very tentative, and must undoubtedly be revised extensively as the fund of experimental and analytical knowledge increases. However, it was felt that a discussion of these subjects at this time, even though it represents only a transient viewpoint, would be of value if it could serve as a stimulus for discussion and a basis for interchange of experimental information and working hypotheses.

ID: CaltechAUTHORS:20150630-124238452

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Abstract: This report covers the underwater performance characteristics of a torpedo shape of the 61 series, designated as Model 61.04 This shape is a modification of Model 61.01, the original form of the 6i series, the tail fin span being reduced and short runners added to the forward part of the cylindrical section and on the fins. All tests were made on models without propellers. The characteristics of Projectile 61.04 are compared with those of Projectile 61.01, for yaw (or pitch) angles up to i2 degrees, and for rudder settings up to 20 degrees. Tests were made, at neutral rudder only, on Projectile 61.04 with the short runners removed from the body and tail fins, to measure the effect of the runners. These tests were authorized by Dr E H Colpitts, Chief of Section 6.1, NDRC, in his letter of October 8 , 1943.

ID: CaltechAUTHORS:20151013-152658208

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Abstract: This memorandum report covers a series of Water Tunnel tests of the Mk 13-2A Torpedo equipped with three different devices designed to facilitate the suspension of the torpedo in standard aircraft bomb racks The suspension fittings tested were: (1) Torpedo Suspension Band Mk 11 (2) Suspension Beam for Mk 13 Air Flask, 30" Centers (3) Suspension Beam for Mk 13 Air Flask, 14" Centers The objective of these tests was to determine what effect the addition of each of these suspension devices would have on the hydrodynamic characteristics of the torpedo. The tests were made on 2-inch diameter models (model scale ratio of 1 to 11.21) in the High Speed Water Tunnel at the California Institute of Technology. The results of these tests are given in Table 1 and in the section on cavitation on Page 10 of this report.

ID: CaltechAUTHORS:20150722-143301660

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Abstract: This report includes measurements of the pressure distribution on the body of the Mk 13 torpedo, Modifications 1, 2, and 2A, and shows the effects of variations in yaw and pitch angle, velocity, and static pressure (i.e., submergence). The measurements were made without propellers. The main objective of the investigation was to determine whether or not the depth control mechanism is actuated by true hydrostatic pressure and to determine, if possible, the cause of the erratic depth-keeping behavior of these torpedoes. In addition, the pressure data is applied to discussing the depth and roll recorder performance, to checking cavitation characteristics, and to evaluating forces and moments acting on the projectile. The important observations and conclusions are presented in the following summary: 1. The pressure on the surface of the torpedo equals the static pressure of the undisturbed water (P = P_0) at two positions, one on the nose and one on the afterbody (Figure 8). Between these two stations (approximately 82% of the body length), the pressure is below static. 2. The position for P = P_0 on the afterbody depends on the proximity of the fins, being slightly farther forward near the fins (Figure 22, Station 19). 3. The position for P = P_0 on the afterbody is only slightly affected by yaw or pitch angles up to 3° (Figures 17 and 18). 4. The measure pressure distributions are unaffected by changes in velocity or static pressure (Figure 23). 5. The existing location of the pressure intake for the immersion gear gives a pressure lower than hydrostatic and causes the torpedo to ride below set depth. 6. True hydrostatic pressure, independent of velocity and small yaw or pitch angles, will be obtained if the immersion gear hydrostat is connect to points midway between the tail fins and about 23" ahead of the tip of the tail. 7. The depth and roll recorder is so located in the exercise head that it is subject to a pressure lower than true hydrostatic and too shallow a depth is recorded. Unfortunately, it is possible for the recorder to indicate the depth to be the set depth when the torpedo rides low, as described in Item 5 above. 8. Since there is no satisfactory location in the exercise head where a pressure connection will give P = = P_0, it is recommended that the included pressure data base used to estimate corrections for application to the recorder in its existing location. 9. Form drag and moment coefficients calculated from pressure distribution data are about 15% higher than given by Water Tunnel measurements while the calculated cross force is 27% lower than measured. 10. The K values for the inception of cavitation on the projectile nose as obtained by actual observation and by prediction from the pressure measurements are in good agreement. It should be noted that these tests were made with the standard fin tail without a shroud ring and some of the above conclusions (particularly Item 6), cannot be expected to apply when the ring is added. Additional measurements with a ring tail are being made.

ID: CaltechAUTHORS:20150722-145341491

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Abstract: This report covers tests made on the Mk 25 torpedo to determine the effect of gas discharged through a horizontal expanding exhaust pipe, being the second supplement to the report, Section No. 6.1-sr207-1275. This testing was requested by Dr. E. H. Colpitts , Chief of Section 6.1 , NDRC , in a letter dated May 4, 1944. As in the two former series of tests, the object was to determine the feasibility of discharging the turbine exhaust gases through the fin structure instead of through the propeller shafts. Several different lengths of exhaust pipe were tested; also runs were made for various values of velocity, submergence, and quantity of gas discharged. Photographs were taken to show the exhaust cavities under the different conditions.

ID: CaltechAUTHORS:20150723-172422354

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Abstract: This report covers Water Tunnel measurements of the infinite aspect ratio characteristics and cavitation characteristics of a hydrofoil section. The profile tested is identical to the 4412 airfoil section of the National Advisory Committee for Aeronautics and is called the NACA 4412 hydrofoil in this report. Measurements and observations include lift, drag, and pitching moment and the inception and development of cavitation as functions of the angle of attack, velocity, and pressure of the flow. The purpose of this report is to present these measurements of the characteristics of this section in water, to compare the results with other available information on this shape, and to evaluate the Water Tunnel method for obtaining the complte hydrodynamic characteristics of hydrofoils.

ID: CaltechAUTHORS:KNAhydrolabrptND-19

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Abstract: This report covers tests made on the MK 25 torpedo to determine the effect of gas discharged through a horizontal exhaust pipe. This report is supplemental to the report, Section No. 6.1-sr207-1275, which described teats with the gas discharged through a vertical fin. It was requested by Dr. E. H. Colpitts, Chief of Section 6.1 NDRC, in a letter dated May 4, 1944. The objective of both this and the former report is to examine the effects of discharging the turbine exhaust gases through the fin structure instead of through the propeller shafts. Since the feasibility of this new method of exhaust discharge is greatly dependent on the effect of the gas flow on the afterbody fin structure and propeller zone, both studies have been restricted to the observation and analysis of this flow. Determination of the effects of the discharge passages and gas stream on the hydrodynamic stability, rudder control, and propeller efficiency have been deferred. Pending the development of an exhaust passage having discharge characteristics that are not visibly unsatisfactory. Several different lengths of exhaust pipe were tested; also, runs were made for various values of velocity and submergence and different amounts of gas discharged. Photographs were taken to show the exhaust cavities created under the different conditions.

ID: CaltechAUTHORS:20150723-171711248

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Abstract: [no abstract]

ID: CaltechAUTHORS:20151013-162305543

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Abstract: This report covers Water Tunnel tests of a 2" diameter model of the hydrobomb, conducted at the Hydraulic Machinery Laboratory at the California Institute of Technology. This work was authorized by Dr. E. H. Colpitts, Chief of Section 6.1, NDRC, as a part of Project OD-99. The purpose of the tests was to determine the drag, cross force, moment, and center-of-pressure eccentricity for various settings of the vertical and horizontal rudders, and also the extent to which these rudders are effective in controlling the torpedo. Runs were also made to determine the cavitation effects produced under the specified operating conditions, namely, a velocity of 70 miles per hour and a submergence of 15 feet. Photographs were taken showing a wide range of cavitation effects. The report includes curves giving the performance characteristics as well as flow line drawings made by observing the model in the Polarized Light Flume. Appendix A gives definitions of the terms used in this report as well as a brief discussion of the required conditions for stability in a projectile.

ID: CaltechAUTHORS:20151020-163912742

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Abstract: This report covers tests of a 2" diameter model of the Mk 25 Torpedo conducted at the Hydraulic Machinery Laboratory of the California Institute of Technology. This work was undertaken as a part of Project NO-176. The purpose of the tests was to determine the effect of the discharge of exhaust through an orifice in the top edge of the vertical fin. Tests were made with and without a shroud ring fitted over the outside of the fins. The model was mounted in the High Speed Water Tunnel with suitable arrangements to pass a measured quantity of gas through the orifice in the fin. Runs were made with varying water velocities, water pressures, and gas quantities. Photographs were taken to show the behaviour of the exhaust gas under these varying conditions.

ID: CaltechAUTHORS:20151020-160717756

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Abstract: This booklet is presented with the compliments of the California Institute of Technology to those attending the meetings of the Soil Conservation Service held on the campus at Pasadena, February 14 to 19, 1944. Its purpose is two-fold : (i) To acquaint our guests with the Cooperative Hydraulics Laboratory and the work of its staff, and (2) to provide notes on the discussions presented by members of the staff at these meetings.

ID: CaltechAUTHORS:20140530-105429366

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Abstract: The High Speed Water Tunnel is operated by the California Institute of Technology under Contract OEMsr-207 with the Office of Scientific Research and Development, and is sponsored by Division Six, Section 6.1, of the National Defense Research Committee. The report covers Water Tunnel tests of 1 - 1/2 " and 2" diameter models of the 2-1/4" AA Rocket Projectile. The drag, cross force, and moment acting on the models were measured and the position of the center of pressure relative to the center of gravity was calculated for various yaw angles. These results were compared with prototype field test data. The main findings are summarized as follows: i. The rocket is statically stable as indicated by a stabilizing moment coefficient and a center-of-pressure eccentricity of more than 0.26. Furthermore, the large area of 1he tail fins will probably provide sufficient damping to make it dynamically stable also. 2. The tail fins cause very large cross force coefficients compared to values for other cylindrical projectiles with folding fin or ring tails. Consequently, unless the rocket is rotated in flight, small misalignments of the tail fins can cause drifting and increase the dispersion seriously . 3. Both the cross force and moment coefficients increase with yaw at a greater than linear rate. 4. Comparison of Water Tunnel and field test data shows good agreement for the moment coefficient 5. The drag coefficient from Water Tunnel tests is 9% lower than the value of 0.46 measured during field tests in air. Scale effects, oscillation of the projectile during free flight tests, and compressibility effects on the drag in air are factors that could account for this difference. 6. The drag is nearly independent of yaw for small angles and increases rapidly for angles greater than about 4°. 7. The high drag coefficient for this projectile is caused by skin friction on the relatively large area of the body and fins and by pressure drag due primarily to a large eddying wake behind the blunt body.

ID: CaltechAUTHORS:20150625-153021146

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Abstract: This report covers tests of a 2" diameter model of the 7.2" Chemical Rocket to determine its performance and possible means of increasing stability and reducing dispersion. The rocket was tested with the two original tails, the ring tail designated herein as No. 61 and the ring tail with extended fins designated No. 62. Three other tail designs were tested designated No. 63, No. 67, and No. 68. Of these, No. 67 was the only one that produced results superior to the No. 61 and No. 62 designs. This No. 67 Tail has extended fins similar to Tail No. 62 and projects beyond the nozzle about one diameter. Details of these tails are given in Figure 12. Tail No. 62 gave a restoring moment 50% greater than Tail No. 61, and Tail No. 67 gave a restoring moment 45% greater than Tail No. 62, both values being for 5° yaw. It is believed that Tail No. 67 represents about the best that can be done in redesigning the tail, as it produced a fairly high moment, a very large center-of-pressure eccentricity, and only one of the five tails tested has a lower drag coefficient. In this connection it should be noted that all the tails tested gave, without exception, adequate stability to the projectile to insure satisfactory flight after burning is completed. Therefore, the only benefit to be obtained from an increase in the stability above that produced by the original ring tail (No. 61) must come from whatever reduction it might effect in the dispersion occurring during the burning of the propellent. Calculation of the period of oscillation of the projectile in flight, and the equivalent wave length, makes possible a comparison of projectile performance from the standpoint of dynamic stability It can be shown that, for rockets with long burning times, the shorter the wave length for a given projectile, the less will be the dispersion. Using this measure of dispersion, Tail No. 67 would be expected to produce 1S% less dispersion than Tail No. 62, and Tail No. 62, i8% less than Tail No 61. This investigation leads to the conclusion that the No. 61, No. 62, and No. 67 Tails will give a high degree of static stability and it is improbable that much more can be accomplished by a redesign of the tail. It is also a fact that the dynamic stability of the projectile cannot be materially improved if its present physical dimensions are to be retained. The conclusion must, therefore, be reached that the most effective means of lowering the dispersion of this rocket is by reducing the malalignment of the jet with the axis of the projectile and eliminating as far as possible asymmetry in the tail assembly.

ID: CaltechAUTHORS:20151014-164322028

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Abstract: This report covers tests to determine the performance of the "Squid" with three designs of nose, designated No. 42, No 45, and No 46. Practically the only difference in the three noses is in the diameter of the flat face, these diameters being 7.90", 8.93", and 9.95", respectively

ID: CaltechAUTHORS:20151014-125950473

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Abstract: The High Speed Water Tunnel is operated by the California Institute of Technology under Contract OEMsr-207 with the office of Scientific Research and Development and is sponsored by Division 6, Section 6.1 of the National Defense Research Committee. This report covers a series of preliminary water tunnel tests of a model of the Mk 13-1, 13-2, and 13-2A torpedoes with shroud ring tails added, and is a supplement to a previous report of this laboratory, entitled "Water Tunnel Tests of the Mk 1.3-1, Mk 13-2, and Mk 13-2A Torpedoes," file marked Section No. 6.1-sr-207-936, and dated November 9, 1943. In the course of the investigation covered by the latter report, it was found that the torpedoes of this series are highly unstable and that they are controllable only within an extremely narrow range of angles of attack. The tests reported herein were, therefore, suggested by this laboratory, and were authorized by Dr. W. V. Houston, Director, Special Studies Group, Columbia University, Division of War Research. The objects of these tests were to investigate the possibilities for improving the stability and controllability of these torpedoes by the use of shroud ring tails, and to discover the trends of variation of these characteristics with variations of the several design factors of the shroud rings. Nine different shroud rings were tested with the torpedo model. It was found that marked improvement of the stability and control angle of these torpedoes may be obtained, without appreciable detriment to other characteristics, by the addition of shroud ring tails. The trends of variation of the stability, control angle, rudder effect, and drag of the torpedo with variations of the shroud ring design were clearly brought out. The results of these tests are shown in Figures 11 to 19, 21 and 22, and are summarized on pages 9 and 10 of this report.

ID: CaltechAUTHORS:20150625-160629322

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Abstract: This memorandum covers water Tunnel Tests of the 15 cm. German Spinner Rocket. The tests were made at the request of the Ballistic Research Laboratory of the Aberdeen Proving Ground. A photograph of the 2" diameter model used for the tests is shown in Figure 2. Overall dimensions of the model and dimensions and physical data for the full-scale projectile are shown in Figure 1.

ID: CaltechAUTHORS:20150717-164406981

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Abstract: This report covers tests on the M-6, 2.36" rocket with the conical pointed nose in combination with on experimental shroud ring toil from the Aberdeen Ballistic Research Laboratory, also with a commercially manufactured Ordnance Deportment shroud ring tail, and with three types of specially made model tails on which the shroud length was varied. One of the specially made model tails was mounted on a plain boom with no nozzle. All of the other tails were mounted on a stepped venturi nozzle.

ID: CaltechAUTHORS:20151014-162631419

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Abstract: This report covers Water Tunnel tests on a 2" diameter model of the "Squid" or British Type "C" Projectile. These tests were conducted for the purpose of determining the performance characteristics of the projectile as well as cavitation effects with varying water pressure. The work was done at the joint request of the British Admiralty Delegation and the Bureau of Ordnance.

ID: CaltechAUTHORS:20151014-163848648

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Abstract: 1. The projectile as ·submitted is quite unstable due to the location of the center of gravity so far aft of the nose. This condition could be greatly improved by making the nose of metal instead of plastic. The tests illustrate how intimately the position of the G.G. is related to stability. Only one of the changes tested failed to increase the stability of the projectile. 2. Extending the tail aft by means of a 1-1/2" boom will add greatly to stability without increasing the drag materially. The effect of this on the interior ballistics of the mortar has not been investigated. 3. A 1-5/16" diameter disc at the rear of the fins would give greater stability than the 1-1/2" boom, but the drag would be increased 70%. This increased drag would probably reduce the range from 10% to 25% depending on the velocity. A 1-1/8" diameter disc would increase the drag about 30% and would have a materially stabilizing effect due to the increased moment and greater center of pressure eccentricity but would not be as stable as the 1-5/16" disc. 4. The stability of projectiles that are now on hand could be increased by the addition of a thin disc held in place by the primer assembly. 5. It is suggested that a number of projectiles be equiped with discs as described in paragraph 4 in order to determine performance under actual conditions. Both the plain and notched discs should be tried. 6. All tests show that the center of pressure location is very sensitive to any changes in the projectile with consequent effect on the stability. It is imperative, therefore, that no other changes than these herein recommended can be made in the projectile if the test results are to apply. If additional changes seem desirable, a new series of tests should be made in order to predict performance.

ID: CaltechAUTHORS:20150630-102542349

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Abstract: The High Speed Water Tunnel is operated by the California Institute of Technology under Contract OEMsr-207 and is sponsored by Division 6, Section 6.1 of the NDRC of the OSRD. The experiments reported in this memorandum were requested by the office of the Chief of Section 6.1. The report presents the results of preliminary measurements of the sound produced in the 20 to 100 kilocycle frequency range by cavitating projectiles in the Water Tunnel working section. Measurements were made of the noise intensity in the 20-100 kilocycle frequency band with three different projectiles. Measurements of the intensity and distribution of the noise within this band were made with one of these projectiles.

ID: CaltechAUTHORS:20151014-110702815

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Abstract: This report covers Water Tunnel tests of a 2.36" rocket projectile with three types of shroud ring tail. Two of the tails are attached by channel section supporting fins to a stepped nozzle, the fins on one of them being stepped to fit the nozzle contour. The third tail has a streamlined nozzle with smooth supporting fins and shroud ring. The results are given of tests with different shroud lengths on the ring tails with the channel section supporting fins.

ID: CaltechAUTHORS:20151014-125552476

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Abstract: This report covers water tunnel tests of a 2.36" rocket projectile with several variations in profile of nose and with two types of tail; a folding fin tail and a fixed shroud ring tail. The hydrodynamic forces, drag, cross wind force, and moment acting on the projectile, were measured and the locations of the center-of- pressure were calculated for the various combinations of noses and tails and at various velocities and yaw angles.

ID: CaltechAUTHORS:20151015-155247079

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Abstract: The High Speed Water Tunnel is operated by the California Institute of Technology under Contract OEMsr-207 and is sponsored by Division 6, Section 6.1 of the NDRC. The tests reported in this memorandum were made at the request of Dr. C. N. Hickman of the NDRC. The report covers water tunnel tests of a 2" diameter model of the 4.5" Rocket Projectile with three different collapsible fin tails and one ring type tail. The drag, crosswind force, and the moment acting on the models were measured and the locations of the center-of-pressure were calculated for various yaw angles.

ID: CaltechAUTHORS:20151020-135945157

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Abstract: This report covers water tunnel tests of a 2" diameter model of a 4.5" rocket projectile (designated in the laboratory as projectile number ND-12) with a fin tail and with the tail replaced by a spinner tube. The purpose of the tests was to determine the magnitude of the hydrodynamic forces acting on the body as functions of its orientation with respect to the direction of motion, and to determine the location of the point of application of those forces.

ID: CaltechAUTHORS:20150623-162955484

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Abstract: [no abstract]

ID: CaltechAUTHORS:20151013-153413665

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Abstract: This report covers water tunnel tests of a full scale 2.37" rocket projectile (designated in the laboratory as projectile number ND-11 Impervium) with four different collapsible tails. The purpose of the tests was to compare the drag coefficients for this projectile using each of the collapsible tails with the drag coefficient for the projectile using its original fixed-fin tail, and to determine the effect of the collapsible type tail on the center-of-pressure location.

ID: CaltechAUTHORS:20151014-112503595

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Abstract: This report covers water tunnel tests of a full scale 21 3/8" long rocket projectile (designed in the laboratory as projectile number ND-11-Impervium). Photographs of the projectile are shown in Figures 1, 2, and 3. The purpose of the tests was to determine the hydrodynamic forces acting on this projectile for different angels of orientation with respect to the flow, and to determine the location of the point of application of the resultant of these forces.

ID: CaltechAUTHORS:20140604-142051766

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Abstract: The high speed water tunnel was established at the California Institute of Technology to study the forces acting upon moving bodies immersed in a fluid. The working section of the tunnel is 14 inches in diameter and 6 feet long and velocities up to 72 feet per second are obtained in it. The model to be tested is mounted on the spindle of a three component balance which measures the drag force, the yaw or lateral force and the moment about the spindle support. The angle of inclination of the model to the flow direction can be adjusted easily. From these measurements are determined the magnitude and location of the resultant forces acting on the model. In order to study cavitation, the pressure in the tunnel is made adjustable and a transparent working section is provided for visual and photographic observations. For qualitative assistance in interpreting the results of the tunnel studies in terms of the effects of the body shapes on the flow pattern, an auxiliary flume is available. The flow is made visible by use of a new technique employing polarized light.

ID: CaltechAUTHORS:20140530-103021693

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Abstract: [No abstract]

ID: CaltechKHR:HydroLabpub167

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