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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenSat, 13 Apr 2024 00:48:14 +0000A Note on Partial Cavitation of Flat Plate Hydrofoils
https://resolver.caltech.edu/CaltechAUTHORS:ACOhydrolabE19-9
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1955
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/p5ya1-44321Flow in Hydraulic Machinery
https://resolver.caltech.edu/CaltechAUTHORS:ACOhydrolabE19-11
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1956
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/m9nt3-e3817Effect of the Volute on Performance of a Centrifugal-Pump Impeller
https://resolver.caltech.edu/CaltechAUTHORS:20140808-115339300
Authors: {'items': [{'id': 'Bowerman-R-D', 'name': {'family': 'Bowerman', 'given': 'R. D.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1957
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 an
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 resulting from the presence of the
volutes. Large real fluid effects, coupled with a 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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vhvmh-m3z91An Experimental Study of Centrifugal-Pump Impellers
https://resolver.caltech.edu/CaltechAUTHORS:20140723-100139088
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Bowerman-R-D', 'name': {'family': 'Bowerman', 'given': 'R. D.'}}]}
Year: 1957
Experimental investigations were made on four two-dimensional impellers and on a well-designed commercial three-dimensional Francis impeller. The over-all performance of each of these impellers was measured and internal-energy loss and pressure-distribution data were also obtained for several impellers. The exit angle of the two-dimensional impellers was fixed and the inlet angle was systematically varied. However, the hydraulic characteristics of these impellers were all found to differ, the source of the variation being in the various loss distributions and hence internal flow patterns in the impellers. The two-dimensional and three-dimensional impeller-loss distributions were also different. The Francis-impeller performance agreed better with potential theory than that of the two-dimensional impellers, and it is included that the different loss distributions of the two types are responsible.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/sarzn-73h53The Effect of a Longitudinal Gravity Field on the Supercavitating Flow Over a Wedge
https://resolver.caltech.edu/CaltechAUTHORS:ACOhydrolabE79-1
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1958
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/2k2fd-ztz40An Experimental Study of Cavitating Inducers
https://resolver.caltech.edu/CaltechAUTHORS:20140722-160825878
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1958
The user of a turbo machine is mainly interested only in the overall hydrodynamic performance of the device. However, the designer is almost always confronted with
the problem of achieving the intended performance in the face of many conflicting hydrodynamic and system requirements. In certain areas it may happen that a
formerly deleterious effect (such as the occurrence of cavitation) can be turned to good advantage as in the case of the supercavitating hydrofoil or propeller. Unfortunately, this happy circumstance is not the lot of the designer of a liquid pumping system when the effects of cavitation are predominant. That this is so, follows from
the fact that the dissipation effects in production of lift by a hydrofoil are relatively unimportant whereas dissipation is important in the decrease of energy of a fluid stream as in the case of a pump.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/8bw81-cbn71Cavitating Flow Past a Cascade of Circular Arc Hydrofoils
https://resolver.caltech.edu/CaltechAUTHORS:ACOhydrolabE79-2
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1960
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qypec-y5m96The Effect of a Longitudinal Gravitational Field on the Supercavitating Flow Over a Wedge
https://resolver.caltech.edu/CaltechAUTHORS:20140722-151924349
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1961
DOI: 10.1115/1.3641650
The free-streamline flow past a symmetrical wedge in the presence of a longitudinal
gravitational field is determined with a linearized theory. The proportions of the cavity
depend upon the cavitation number and Froude number. The drag coefficient is likewise
affected by gravity, though to a smaller extent.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9eneh-jyy26Note on Observations of Cavitation in Different Fluids
https://resolver.caltech.edu/CaltechAUTHORS:20140826-112659690
Authors: {'items': [{'id': 'Sarósdy-L-R', 'name': {'family': 'Sarósdy', 'given': 'L. R.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1961
DOI: 10.1115/1.3658979
Many observations [1, 2, 3] have shown that the
performance of a centrifugal pump with different fluids or with the same fluid at different temperatures is not the same at the same cavitation number when the latter is based upon the vapor pressure of the bulk fluid. Various similarity rules have been put forward in these works to account for the observed effect; namely, that lower net positive suction heads are achievable in
most cases compared to those observed in cold tap water. This difference is ascribed to the thermal effect associated with evaporating a certain fraction of the bulk fluid and the attendant decrease of vapor pressure. Scaling rules of the vapor-pressure decrease are made by assuming the process static and that all of the fluid in the inlet of the pump is at the same pressure. The measurements
of Salemann [4] show that such a simple concept is
inadequate, and he offers further speculations about the nature of the cavitation process as do Acosta and Hollander [5]. The purpose of this note is to describe an experiment intended to show the types of cavitation that occur and, where possible, to measure directly the reduction of vapor pressure or net positive suction head observed in pump experiments.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/kqrch-vxz94Simulated Wave-Riding Dolphins
https://resolver.caltech.edu/CaltechAUTHORS:20140902-163757910
Authors: {'items': [{'id': 'Perry-B', 'name': {'family': 'Perry', 'given': 'Byrne'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Kiceniuk-T', 'name': {'family': 'Kiceniuk', 'given': 'Taras'}}]}
Year: 1961
DOI: 10.1038/192148a0
The explanation of the mechanism by which
dolphins are able to ride bow waves of ships, or
natural surf and wind-generated waves, has stimulated
much discussion and controversy. Since an
excellent summary of previous research on the wave-riding
problem has been given by Fejer and Backus,
only a few remarks by way of review will be given
here.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rg49y-jha90Cavitation in Turbopumps -- Part 1
https://resolver.caltech.edu/CaltechAUTHORS:20140807-160450346
Authors: {'items': [{'id': 'Stripling-L-B', 'name': {'family': 'Stripling', 'given': 'L. B.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1962
DOI: 10.1115/1.3657314
A free-streamline flow through a cascade of semi-infinite flat plates is taken as a simplified model of the cavitation process in a helical inducer pump. The length and thickness of the resulting cavity is determined as a function of blade geometry and cavitation parameter. Loss coefficients resulting from the cavitation are estimated and representative cavity shapes are calculated to aid in designing the leading edge shape of the blades.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rwhkh-7kg58Measurements on fully wetted and ventilated ring wing hydrofoils
https://resolver.caltech.edu/CaltechAUTHORS:ACOhydrolabrptE-138-1
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Bate-E-R-Jr', 'name': {'family': 'Bate', 'given': 'E. R., Jr.'}}, {'id': 'Kiceniuk-T', 'name': {'family': 'Kiceniuk', 'given': 'T.'}}]}
Year: 1965
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9s63k-ha937Some New Measurements On the Drag of Cavitating Disks
https://resolver.caltech.edu/CaltechAUTHORS:20140902-153543380
Authors: {'items': [{'id': 'Klose-G-J', 'name': {'family': 'Klose', 'given': 'G. J.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1965
As part of an experiment on unsteady flow past a cavitating circular disk, it was necessary to make calibrating measurements of the drag on disks in steady flow. The measurements were made for greater cavitation numbers than have been previously recorded, and show that the drag coefficient is essentially linearly dependent upon cavitation number up to values of this parameter as high as 1.3.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/10js0-d3111Observations on the Performance of Centrifugal Pumps at Low Reynolds Numbers
https://resolver.caltech.edu/CaltechAUTHORS:20140722-162608189
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Hollander-A', 'name': {'family': 'Hollander', 'given': 'A.'}}]}
Year: 1966
From the results presented herein it is clear that
the viscous flow in the centrifugal pump impeller is
very complicated, but we see that the internal flow itself
is not necessarily too inefficient and further that
the hydraulic torque does not necessarily increase with
lower Reynolds numbers. These results mean that the
effect of external disc friction and its interaction in
the volute are as important as the impeller design itself
for such viscous flows. The present tests suggest that
a pump which works well at high Reynolds numbers, as for
water application, will not necessarily be the best pump
for the low Reynolds number application. These internal
flows are certainly very complicated and the authors hope
that some of the techniques and suggestions made herein
will be used for such work by others in the future.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/cqm60-9n284Experimental Observations on the Flow Past a Plano-Convex Hydrofoil
https://resolver.caltech.edu/CaltechAUTHORS:20140820-094641740
Authors: {'items': [{'id': 'Wade-R-B', 'name': {'family': 'Wade', 'given': 'R. B.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1966
DOI: 10.1115/1.3645828
Some new measurements and observations on the noncavitating and cavitating flow past a plano-convex hydrofoil are presented. Under some conditions of partial cavitation, strong, periodic oscillations both in the cavity length and forces exerted on the hydrofoil are observed. The reduced frequency of oscillation depends upon the cavitation number and angle of attack; it also depends somewhat on tunnel speed for the lower angles of attack but becomes substantially independent of speed for the highest angle. The peak-to-peak magnitude of the force oscillation can amount to about 20 percent of the average force.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/x0fpa-4p663Experiments On Gravity Effects in Supercavitating Flow
https://resolver.caltech.edu/CaltechAUTHORS:20140820-103603055
Authors: {'items': [{'id': 'Kiceniuk-T', 'name': {'family': 'Kiceniuk', 'given': 'T.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1966
Experiments on the effect of a transverse gravitational field on the supercavitating flow past a wedge tend to confirm predictions based on linearized free-streamline theory. A small though systematic dependence upon Froude number not accounted for by the existing theory is revealed, however.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0s3dr-nm559Measurements on Fully Wetted and Ventilated Ring Wing Hydrofoils
https://resolver.caltech.edu/CaltechAUTHORS:20140723-093249667
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Kiceniuk-T', 'name': {'family': 'Kiceniuk', 'given': 'T.'}}, {'id': 'Bate-E-R-Jr', 'name': {'family': 'Bate', 'given': 'E. R., Jr.'}}]}
Year: 1967
DOI: 10.1115/1.3610082
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, at a fixed total included cone angle of 12 deg. The fully welted flows all exhibited separation from the
leading edge except for the largest diameter-chord ratio, a result which has been attributed to excessive cone angle. 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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/7s24r-5xz59Investigation of Cavitating Cascades
https://resolver.caltech.edu/CaltechAUTHORS:20140820-140422046
Authors: {'items': [{'id': 'Wade-R-B', 'name': {'family': 'Wade', 'given': 'R. B.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1967
DOI: 10.1115/1.3609687
Experiments on cavitating and noncavitating cascades were carried out in a conventional water tunnel modified for this purpose. The comparison of the experimental results with theory, in both the fully wetted and fully cavitating conditions, was found to be satisfactory.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/3m2yq-phr65Unsteady Force Measurements On Fully Wetted Hydrofoils in Heaving Motion
https://resolver.caltech.edu/CaltechAUTHORS:20140902-114603469
Authors: {'items': [{'id': 'Klose-G-J', 'name': {'family': 'Klose', 'given': 'G. J.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1968
An experimental investigation is reported of the unsteady forces due to heaving motion of fully wetted hydrofoils of unity aspect ratio and also in two-dimensional flow. The tests covered a broad range of reduced frequency and determined the effects of variation in submergence depth, angle of attack, oscillation amplitude, and flow velocity. In general, the findings agree well with available theoretical calculations, but some unexpected variations were found for the case of a wedge-shaped foil and for changes in angle of attack.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/p1bnk-spj73Quasi Two-Dimensional Flows Through a Cascade
https://resolver.caltech.edu/CaltechAUTHORS:20140829-144332902
Authors: {'items': [{'id': 'Mani-R', 'name': {'family': 'Mani', 'given': 'R.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1968
DOI: 10.1115/1.3609146
A thin airfoil theory is developed for airfoils spanning a slowly diverging or converging channel, the motivation being to predict, theoretically, the effect of varying axial velocity on the cascade performance of axial flow compressor rows.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/1qqjn-qes59Note on an Airfoil in a Slightly Non-uniform Stream
https://resolver.caltech.edu/CaltechAUTHORS:20140715-100418164
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Mani-R', 'name': {'family': 'Mani', 'given': 'R.'}}]}
Year: 1968
DOI: 10.1007/BF00382331
An investigation is presented of the modifications that must be made to
two-dimensional calculations of the flow past an airfoil when the flow takes
place in a symmetric channel with slightly non-parallel walls.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/46yee-8qk57A Note on Turbopump Blade Cavitation Compliance for the POGO Instability
https://resolver.caltech.edu/CaltechAUTHORS:BREpff72
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1972
During the first or booster stage of flight many liquid-propellant rockets have experienced severe longitudinal vibrations caused by a closed loop interaction between the first longitudinal structural mode and the dynamics of the propulsion system. This, "POGO" instability, reviewed in Reference 1, has been the subject of intensive research since it was first encountered. One of the most important transients in the dynamic modelling of the propulsion system is the "cavitation compliance" of the turbopumps [3] defined as the negative of the derivative of the cavity and bubble volume in the pump and its suction line with respect to the section pressure. Thus, it describes the oscillatory source/sink behavior of the pump due to changes in the cavity volume. Past analyses [1, 2] have suggested dividing this compliance into two components corresponding to the two major types of pump cavitation, namely blade cavitation and back-flow cavitation.
The purpose of this paper is to present some preliminary results of theoretical calculations of blade cavitation compliance. The most satisfactory starting point would be a theory for unsteady cavitating flow in a cascade. Whilst work on this is in progress at the present time, the low frequency or quasistatic approach based on existing steady flow theory is much simpler and in itself yields interesting results.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/bt893-vwf43Hydrofoils and hydrofoil craft
https://resolver.caltech.edu/CaltechAUTHORS:ACOarfm73
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1973
DOI: 10.1146/annurev.fl.05.010173.001113
At the present time several hundred hydrofoilcraft are in service throughout the world. The upsurge in the use of these craft did not really begin until the late 1950s,
although fascination with the idea of supporting small boats with underwater wings dates well back into the nineteenth century. About the turn of the century, hydrofoil flight was achieved, to be followed in a few years by Bell and Baldwin who, at the close of World War I, achieved the modern hydrofoil speed of 60 knots in a very novel craft. Progress and interest in this form of transportation then waned for many years. There were some interesting developments just prior to and through World War II in Europe, and after the war interest quickened in several countries. Current thinking at this time may be judged by Gabdelli & von Karman (1950), who note that the drag of surface vessels may be decreased by lifting the floating structure with hydrofoils. But they go on to add that they "... do not attempt to estimate the effect of such a radical innovation; whether the trials until now appear promising is a question of individual judgment." As subsequent events have proven, the trials were indeed promising. The many hydrofoil craft now in service are of several different types and a number of more advanced concepts are being developed swiftly.
Greater speed in all forms of transportation has always been sought, provided the price is not too great. The air-sea surface is a particularly inhospitable environment for major advances in operating speed, yet it is partly this advance that is the stimulus for hydrofoil craft as well as that for conventional marine craft and the newer hover craft. Silverleaf (1970) and Silverleaf & Cook (1970) review all these recent developments from technical and economic standpoints. High speeds at sea are now possible, they observe, but may not be attained for lack of naval or commercial demands.
The successful achievements of hydrofoil craft to date and the possibility of high speeds at sea are due to the greatly increased understanding in recent years of the flow past hydrofoils and also to the development of foil configurations and control systems for coping with the roughness of the sea surface. It seems appropriate, therefore, in this review to link the discussion of hydrofoils with that of progress in the craft, for the two are very interdependent. This interaction has been the source of a great deal of research in applied fluid mechanics in recent years. The methods of analysis, experiment, and design in this field follow closely those in aeronautics, yet there are some important differences because of the medium itself. These include the phenomena due to the free surface (an ever-present boundary in naval hydrodynamics) and the possibility of a phase change through cavitation or ventilation with consequent important modification of the flow; because the liquid density is so much greater than in equivalent aeronautical applications, the dynamic response to motions must be treated very carefully. Hydrofoils, in addition, find application as control surfaces and structural members in marine craft generally, and serve also as elements of propulsion devices.
In what follows, the general characteristics of hydrofoil craft are briefly reviewed together with some representative modern examples. Some physical aspects of the flow past hydrofoils are then described, followed by a resume of some of the recent methods used in design and analysis of hydrofoils. In this short account several important topics have of necessity been omitted; these include propulsion, hydroelastic problems, and ship motions, each of which could serve as the topic of a separate article.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/jpen9-1tj68Theoretical, Quasi-Static Analysis of Cavitation Compliance in Turbopumps
https://resolver.caltech.edu/CaltechAUTHORS:BREjsr73
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1973
The serious POGO instability experienced by many liquid propellant rockets results from a closed loop interaction between the first longitudianl structural mode of vibration and the dynamics of the propulsion system. One of the most important features in the latter is the cavitation compliance of the turbopumps. This report presents calculations of the blade cavitation compliance obtained from free streamline cascade theory and demonstrates the various influences of angle of attack, blade angle, blade thickness and cavitation number. Discrepancies between calculated and experimentally derived values are discussed.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/nhny9-p4y89A Note on the Calculation of Supercavitating Hydrfoils with Rounded Noses
https://resolver.caltech.edu/CaltechAUTHORS:FURjfe73
Authors: {'items': [{'id': 'Furuya-O', 'name': {'family': 'Furuya', 'given': 'O.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1973
Practical supercavitating hydrfoils have rounded leading edges for mechanical strength. The prediction of pressures near the leading edge of such hydrofoils by linearized free streamline theory fails because singularities are usually required there by the theory. A simple method based on singular perturbations of avoiding these difficulties for hydrofoils which have parabolic noses but an arbitrary profile downstream of the leading edge is presented. The results of such a computation on a hydrofoil with a parabolic profile and with fixed cavity separation near the leading edge radius are shown and are compared with an exact free-streamline theory. The agreement is excellent.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/bq5bb-zxm56Viscous Effects in the Inception of Cavitation on Axisymmetric Bodies
https://resolver.caltech.edu/CaltechAUTHORS:ARAjfe73
Authors: {'items': [{'id': 'Arakeri-V-H', 'name': {'family': 'Arakeri', 'given': 'V. H.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1973
Cavitation inception and development on two axisymmetric bodies was studied with the aid of a Schlieren flow visualization method developed for that purpose. Both bodies were found to exhibit a laminar boundary layer separation; cavitation inception was observed to occur within this region of separated flow. The incipient cavitation index was found to be closely correlated with the magnitude of the pressure coefficient at the location of flow separation on one of the bodies. There is also experimental evidence that events at the site of turbulent reattachment of the separated flow may also greatly influence cavitation inception.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/djgj3-7xn33A Note on the Unsteady Cavity Flow in a Tunnel
https://resolver.caltech.edu/CaltechAUTHORS:KIMjfe74
Authors: {'items': [{'id': 'Kim-J-H', 'name': {'family': 'Kim', 'given': 'J. H.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1974
The unsteady internal cavitating flow such as the one observed in a pump or a turbine is studied for a simple two-dimensional model of a base-cavitating wedge in an infinite tunnel and it is shown how the cavitation compliance can be calculated using the linearized free streamline theory. Numerical values are obtained for the limiting case of a free jet. Two important features are: First, the cavitation compliance is found to be of complex form, having additional resistive and reactive terms beyond the purely inertial oscillation of the whole channel in "slug flow." Second, the compliance has a strong dependence on frequency.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/dyg8t-bqe22The Dynamic Performance of Cavitating Turbopumps
https://resolver.caltech.edu/CaltechAUTHORS:CEBcfm75
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}]}
Year: 1975
Knowledge of the dynamic performance of turbopumps is essential for the prediction of instabilities in hydraulic systems; the necessary information is in the form of a transfer function relating the instantaneous pressures and mass flow rates at inlet and discharge. Cavitation has a significant effect on this transfer function since dynamical changes in the volume of cavitation contribute to the difference in the instantaneous flow rates. The present paper synthesizes the transfer matrix for cavitating inducers at moderately low frequencies and shows that the numerical results are consistent with observations on rocket engine turbopumps.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vf0we-yrf16Some transition and cavitation inception observations on a 1.5 cal ogive
https://resolver.caltech.edu/CaltechAUTHORS:20150410-103711329
Authors: {'items': [{'id': 'Arakeri-V-H', 'name': {'family': 'Arakeri', 'given': 'V. H.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1975
Transition observation on a 1. 5 cal ogive were carried out by Schlieren technique of flow visualization up to Re_D of 1.26 x 10^6. Good agreement is found between computed position of transition by Smith method and those observed by Schlieren technique for tunnel velocities greater than 50 fps (Re_D> 7.85 x 10^5). Cavitation under desinent conditions at tunnel velocities of 30 fps and 40 fps was found to occur within the transition region of the boundary layer. At 50 fps good agreement is found between the present value of inception cavitation index, the value of desinent cavitation index measured by Parkin and the negative value of the pressure coefficient at both predicted and observed positions of transition. These observations strongly suggest that cavitation inception is closely related to transition on smooth bodies at supercritical Reynolds numbers.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0kgy6-7de38Cavitation inception
https://resolver.caltech.edu/CaltechAUTHORS:20150413-101139951
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Parkin-B-R', 'name': {'family': 'Parkin', 'given': 'B. R.'}}]}
Year: 1975
We are sure that the delegates to the present conference do not need to be reminded that cavitation inception in the pervasive role it occupies in Naval Architectural hydrodynamics remains as a basic problem bedevilling the worker in the laboratory and field alike. One of the more perplexing aspects of this phenomenon has been its lack of repeatability between experiments carried out on similar test bodies in different test facilities or even on different types of bodies in the same test facility. In addition, in sea trials, the conditions under which it occurs are seldom well defined. There is the further problem of accounting properly for the effects of modifying the test fluid itself either by a change in state point or by the addition of an additional liquid solute such as a long chain polymeric molecule or finely divided particulate matter. Underlying all these considerations is the ultimate goal of extrapolating laboratory findings to representative field conditions; in the present context, these are the various conditions of the marine environment. This specific point was addressed briefly in the concluding discussion on cavitation inception of the 16th conference in which the onus of reporting progress towards this goal was laid upon the present authors. It would indeed be gratifying to report to the present conference that our experimental techniques are now sufficiently advanced to simulate properly all of the important prototype conditions even if we had precise knowledge of them. This is, regrettably, not yet the case, but there have been nevertheless solid advances in certain areas of cavitation inception research which make one hopeful for the future. We have selected three such areas to report on to the present conference; viz, surface inception, vortex cavitation and scaling, and the effects of polymer additive on inception. In addition, we refer briefly to current methods of observation/measurement of cavitation nuclei as this is a subject of paramount importance to the cavitation process itself and also because we suspect such measurement will become an important part of laboratory testing in the near future.
In the material to follow we have tried to emphasize the phenomena and techniques themselves leaving to a future occasion a full assessment of inception scaling theories. We have not attempted to be encyclopedic in coverage as there are recent excellent texts and survey articles, e.g. Arndt (1971), Eisenberg (1969), Eisenberg and Tulin (1961), Knapp et al (1970), Robertson and Wislicenus (1969) Grein (1973) which cover the field, and we should also state that in so doing any serious omissions we may have made are not intentional!https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/whf8e-k4e29Unsteady Flow in Cavitating Turbopumps
https://resolver.caltech.edu/CaltechAUTHORS:KIMjfe75
Authors: {'items': [{'id': 'Kim-J-H', 'name': {'family': 'Kim', 'given': 'J. H.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1975
Unsteady flow in a cavitating axial inducer pump is analyzed with the help of a simple two-dimensional cascade model. This problem was motivated by a desire to study the effect of unsteady cavitation on the so-called POGO instability in the operation of liquid rocket engines. Here, an important feature is a closed loop coupling between several different modes of oscillation, one of which is due to the basic unsteady characterisitcs of the cavitation itself. The approaching and leaving flow velocities up- and downstream of the inducer oscillate, and the cavity-blade system participates dynamically with the basic pulsating flow. In the present work, attention is focused on finding a transfer matrix that relates the set of upstream variables to those downstream. This quantity, which is essentially equivalent to cavitation compliance in the quasistatic analyses, is found to be complex and frequency dependent. It represents the primary effect of the fluctuating cavity in the system. The analysis is based on a linearized free streamline theory.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qenvv-q8d13Cavitation Inception - A Selective Review
https://resolver.caltech.edu/CaltechAUTHORS:ACOjsr75
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Parkin-B-R', 'name': {'family': 'Parkin', 'given': 'B. R.'}}]}
Year: 1975
This paper reviews recent developments in selected cavitation research areas which have been active mainly within the past two years. The new understanding resulting from this work is summarized. Research topics discussed are cavitation inception on smooth surfaces, on vortex cavitation and scaling, on the measurement of cavitation nuclei, and on the effects of polymer additives. Because of the selective nature of the review, a fairly comprehensive listing of recent contributions to the literature on these and related aspects of cavitation research is an essential part of the exposition.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9jmyt-qrf21The Dynamic Transfer Function for a Cavitating Inducer
https://resolver.caltech.edu/CaltechAUTHORS:BREjfe76
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1976
Knowledge of the dynamic performance of pumps is essential for the prediction of transient behavior and instabilities in hydraulic systems; the necessary information is in the form of a transfer function which relates the instantaneous or fluctuating pressure and mass flow rate at inlet to the same quantities in the discharge from the pump. The presence of cavitation within the pump can have a major effect on this transfer function since dynamical changes in the volume of cavitation contribute to the difference in the instantaneous inlet and discharge mass flow rates. The present paper utilizes results from free streamline cascade theory to evaluate the elements in the transfer function for a cavitating inducer and shows that the numerical results are consistent with the characteristics observed in some dynamic tests on rocket engine turbopumps.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ync46-h9953Unsteady Effects in Flow Rate Measurement at the Entrance of a Pipe
https://resolver.caltech.edu/CaltechAUTHORS:ACOjfe76
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1976
Unsteady flow in pipes and nozzles occur frequently in engineering applications and they pose special problems of measurement and calibration. When the Reynolds number is high the entrance region of a pipe (following a smooth contraction) is characterized by a thin boundary layer and the unsteady effects are then bound up in the unsteady behavior of the boundary layer. Woblesse and Farrell [1]2 have recently considered unsteady effects in laminar pipe entrance flows that start from rest by an integral method. Periodic disturbances also arise which require a different treatment. The primary interest of the present work is for thin entrance boundary layers subject to peridodic disturbances. In either case the ratio of the average velocity to the velocity in the potential core is
V[sub]avg/V[sub]core = 1- 2[delta]*/R [equation 1]
where [delta]* is the usual displacement thickness and R is the pipe radius. In steady flow this ratio is just the "discharge coefficient", c[sub]d. In unsteady flow it is very desirable to know how this ratio changes with time because many of the presently available experimental methods enable one to measure V[sub]core but not V[sub]avg readily. In this brief note we will estimate the unsteady effects of a periodic, fluctuating main flow on the displacement thickness of a laminar, flat plate boundary layer. It is assumed that the boundary layer is sufficiently thin compared to the radius of a pipe so that the pressure gradient caused by this effect in a pipe can be neglected; the results should then be directly applicable to equation (I).https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/8fp2k-74809A Brief Note on Linearized, Unsteady, Supercavitating Flows
https://resolver.caltech.edu/CaltechAUTHORS:ACOjsr79
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Furuya-O', 'name': {'family': 'Furuya', 'given': 'O.'}}]}
Year: 1979
Three different models for the unsteady fluctuations of a slender cavity in the limit of small reduced frequency are compard with the results of quasi-steady calculations. Tullin's kinematically closed model in unsteady flow in soon to tend smoothly to a limiting quasi-steady motion having the same value for the compliance of the cavitating flow, unlike other models that have been used in the past.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/abf38-myd50A Test Program to Measure Fluid Mechanical Whirl-Excitation Forces in Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:BREriphpt80
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1980
Much speculation has surrounded the possible unsteady hydrodynamic forces which could be responsible for the excitation of whirl instabilities in turbomachines. However there exist very few measurements of these forces which would permit one to evaluate the merits of the existing fluid mechanical analyses. In keeping with the informal nature of this workshop we will present details of a proposed test program for the measurement of the unsteady forces on centrifugal impellers caused by either (i) azimuthal asymmetry in the volute geometry or (ii) an externally imposed whirl motion of the impeller. In the second case the forces resulting from the imposed whirl motions with frequencies ranging from zero to synchronous will be measured by means of a force balance upon which the impeller is mounted. This work is presently being carried out under contract with the NASA George Marshall Space Flight Center, Huntsville, Alabama (Contract NAS 8-33108).https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/jjytr-3n908A Brief Note on the Interaction of an Actuator Cascade with a Singularity
https://resolver.caltech.edu/CaltechAUTHORS:CHAriphpt80
Authors: {'items': [{'id': 'Chamieh-D-S', 'name': {'family': 'Chamieh', 'given': 'D.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1980
We have recently become concerned with making estimates of steady forces that may be exerted between moving blade rows and stationary blade rows or volutes. Our present interest is with time averaged forces for estimation of shaft loads and flow asymmetry forces rather than with transient processes. For this purpose we have adopted the well-known "actuator" model for the blade row in which the flow leaving the row or cascade is assumed to have a constant leaving angle. The disturbances external to this row such as a volute may be represented by distributions of vortex elements as was done for example by Domm and Hergt [1].https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/r1tac-56m66Synfuel systems. A review of letdown devices and other multiphase flow problems
https://resolver.caltech.edu/CaltechAUTHORS:CHA048
Authors: {'items': [{'id': 'Charles-A-L', 'name': {'family': 'Charles', 'given': 'A. L.'}}, {'id': 'Chelvakumar-Kasivisvanathan', 'name': {'family': 'Chelvakumar', 'given': 'K.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1981
In an effort to develop domestic sources of energy, a number of processes to convert coal to clean fuels have been investigated. Products of these processes span the range from clean coal substitutes, to synthetic crude oil, to synthetic natural gas. Some of these processes, after successful operation in the laboratory, are now operating on a pilot plant scale to determine the feasibility of further scale up. These pilot plants range in capacity from 1/1000 to 1/10 of that projected for commercial operation [1]. At the pilot plant scale, problem areas which are generic to the conversion process have come to light. These problem areas include: handling of highly abrasive slurries, three phase heat transfer, high temperatures, high pressure, and high pressure slurry letdown.
In this report the problems associated with high pressure slurry letdown from the reactor/dissolver to the fractionating section will be discussed. The operating experience and the current state of the art for high pressure letdown valves in the coal conversion industry and the process industry will be examined. Also, the commonly used valve sizing techniques will be examined in relation to the problem of sizing for high pressure letdown. A summary of the instrumentation needed to monitor the letdown process for valve development, and ultimately for process control, is also included.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/a63x2-z8p81Observations of nuclei in cavitating flows
https://resolver.caltech.edu/CaltechAUTHORS:20201120-120817537
Authors: {'items': [{'id': 'Katz-Joseph', 'name': {'family': 'Katz', 'given': 'Joseph'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan'}}]}
Year: 1982
DOI: 10.1007/978-94-009-7532-3_11
The present report focuses on the source of the large difference between the theoretical strength of pure liquid and the actual tension that is required to initiate cavitation in technical fluids such as test facilities and natural waters. This discrepancy is commonly explained by the existence of nuclei, either solid particles or vapor and gas bubbles that permit phase transition to take place near equilibrium. The existence of these nuclei, their source and lifetimes have occupied much space in the technical literature for decades. Yet, direct observations of tests in applications to naval hydrodynamics and hydraulic machinery flows has not provided much information about these nuclei. Their existence, however, and their effect on cavitation is in no doubt as is demonstrated by the series of photographs of a propeller that were taken in the 'Vacu-Tank' of NSMB shown in Figure 1. There, addition of 'nucleating' sources to the water by electrolysis clearly increases the number of visible cavitating bubbles on the blade surfaces.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/js1zv-4f915Observations of Nuclei in Cavitating Flows
https://resolver.caltech.edu/CaltechAUTHORS:KATasr82
Authors: {'items': [{'id': 'Katz-J', 'name': {'family': 'Katz', 'given': 'Joseph'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan'}}]}
Year: 1982
The present report focuses on the source of the large difference between the theoretical strength of pure liquid [12] and the actual tension that is required to initiate cavitation in technical fluids such as test facilities and natural waters. This discrepancy is commonly explained by the existence of nuclei, either solid particles or vapor and gas bubbles that permit phase transition to take place near equilibrium. The existence of these nuclei, their source and lifetimes have occupied much space in the technical literature for decades [1, 2, 3, 8]. Yet, direct observations of tests in applications to naval hydrodynamics and hydraulic machinery flows has not provided much information about these nuclei. Their existence, however, and their effect on cavitation is in no doubt as is demonstrated by the series of photographs of a propeller that were taken in the 'Vacu-Tank' of NSMB [9] shown in Figure 1. There, addition of 'nucleating' sources to the water by electrolysis clearly increases the number of visible cavitating bubbles on the blade surfaces.
The importance of these nuclei has led to the development of several detection and observation techniques [4, 6, 10, 11]. These include the microscopic observation of water samples, the 'coulter counter', 'single particle light scattering', the 'acoustic' techniques for detection of gas bubbles, holograms with microscopic observation of the reconstructed image, and finally the venturi 'liquid quality' meter [11].
Some results of the nuclei number density distribution function N(R) that were accumulated from various sources [6] in different experimental facilities and some open sea measurements are presented in Figure 2. The results include holographic observation in the Caltech HSWT which are found to be mostly solid particles and the Caltech LTWT which are found to be mostly bubbles. This difference in the type of nuclei may explain why is it easier to cavitate the same body in the LTWT (provided that the flow is non-separating) while the liquid in the HSWT can support a certain tension [6]. Note the several orders of magnitude difference in the populations shown and the correspondence between the oceanic acoustic measurements of Medwin [10] that display the population of bubbles and the holographic observations of plankton [5, 13]. It is interesting that some of these facilities are well above the 'natural' levels and it may be inferred that the Vacu-Tank may be well below. Thus, significant 'scaling' errors may occur while applying laboratory results to field cavitation phenomena [1, 2, 3].https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/yjtpj-gjn20Experimental Measurements of Hydrodynamic Stiffness Matrices for a Centrifugal Pump Impeller
https://resolver.caltech.edu/CaltechAUTHORS:CHAriphpt82
Authors: {'items': [{'id': 'Chamieh-D-S', 'name': {'family': 'Chamieh', 'given': 'D. S.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}, {'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R.'}}]}
Year: 1982
The objective of the Rotor Force Test Facility at the California Institute of Technology is to artificially orbit the center of rotation of an impeller enclosed within a volute over a range of frequencies from zero to synchronous and to measure the resulting forces on the impeller. This paper reports preliminary data from the first stage experiments in which the shaft is orbited at low frequency. Steady volute forces along with stiffness matrices due to the change in position of the rotor center are measured. Static pressure taps around the volute are used to obtain volute pressure distributions for various fixed positions of the impeller center and for various flow rates. Static pressure forces are calculated from these pressure distributions allowing a more complete analysis of the components of the impeller forces. Comparison is made with various existing theoretical and experimental results.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/x3tzr-6gw30On the linearized dynamics of two-dimensional bubbly flows over wave-shaped surfaces
https://resolver.caltech.edu/CaltechAUTHORS:20130725-163717360
Authors: {'items': [{'id': "d'Agostino-L", 'name': {'family': "d'Agostino", 'given': 'L.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1984
In the last decades the technological importance or bubbly
flows has generated considerable efforts to achieve a
better understanding of their properties, [1],[2]. However,
the presence or two interacting phases so much increases
the complexity or the problem that a satisfactory
mathematical model of these flows has been possible only in
special cases under fairly restrictive simplifying assumptions.
The main purpose of the present note is to investigate
the effects due to the inclusion or bubble dynamic response
in two-dimensional flows over wave-shaped surfaces.
The earlier studies of bubbly flows based on space averaged
equations for the mixture in the absence or relative
motion between the two phases, [5], [6], do not consider
bubble dynamic effects. This approach simply leads to an
equivalent compressible homogeneous medium and has
been used to analyze the behaviour or one-dimensional bubbly
flows through converging-diverging nozzles.
In order to account for bubble dynamic response, in a
classical paper by Foldy, [7], each individual bubble is
described as a randomly distributed point scatterer. Assuming
that the system is ergodic, the collective effect of bubble
dynamic response on the flow is then obtained by taking the
ensemble average over all possible configurations. An alternative
way to account for bubble dynamic effects would be
to include the Rayleigh-Plesset equation in the space averaged
equations. Both methods have been successfully
applied to describe the propagation or one-dimensional perturbances
through liquids containing small gas bubbles, [8],
[9], [10], [11].
However, because of their complexity, there are not many
reported examples of the application to specific flow
geometries of the space averaged equations which include
the effects of bubble response, [12]. In an earlier note, [13],
we considered the one-dimensional time dependent linearized
dynamics or a spherical cloud of bubbles. The results
clearly show that the motion of the cloud is critically controlled
by bubble dynamic effects. Specifically, the dominating
phenomenon consists of the combined response of the
bubbles to the pressure in the surrounding liquid, which
results in volume changes leading to a global accelerating
velocity field. Associated with this velocity field is a pressure
gradient which in turn determines the pressure encountered
by each individual bubble in the mixture.
Furthermore, it can be shown that such global interactions
usually dominate any pressure perturbations experienced
by one bubble due to the growth or collapse or a neighbor
(see section 5).
In the present note the same approach is applied to the
two-dimensional case or steady flows over wave-shaped surfaces
(for which there exist well established solutions for
compressible and incompressible flow), With the aim, as previously
stated, of assessing the effects due to the introduction
or bubble dynamic response. Despite its intrinsic limitations,
the following linear analysis indicates some of the
fundamental phenomena involved in such flows and provides
a useful basis for the study of the same flows with
non-linear bubble dynamics, which we intend to discuss in a
later publication. The present extention to the case of bubbly
flows over arbitrarily shaped surfaces also constitutes
the starting point for the investigation or such flows, a problem
of considerable technical interest, for example in cavitating
flows past lifting surfaces.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9ndb4-60d20Two-Dimensional Unsteady Analysis of Fluid Forces on a Whirling Centrifugal Impeller in a Volute
https://resolver.caltech.edu/CaltechAUTHORS:TSUriphpt84
Authors: {'items': [{'id': 'Tsujimoto-Y', 'name': {'family': 'Tsujimoto', 'given': 'Y.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}]}
Year: 1984
Destabilizing fluid forces on a whirling centrifugal impeller rotating in a volute have been observed (Ref. 1). A quasisteady analysis neglecting shed vorticity (Ref. 2) or an unsteady analysis without a volute (Ref. 3) does not predict the existence of such destabilizing fluid forces on a whirling impeller.
The present report is intended to take into account the effects of a volute and the shed vorticity. We treat cases when an impeller with an infinite number of vanes rotates with a constant velocity [omega] and its center whirls with a constant eccentric radius {epsilon] and a constant whirling velocity [omega].https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/tgy38-7hz78Hydrodynamic Impeller Stiffness, Damping, and Inertia in the Rotordynamics of Centrifugal Flow Pumps
https://resolver.caltech.edu/CaltechAUTHORS:JERriphpt84
Authors: {'items': [{'id': 'Jery-B', 'name': {'family': 'Jery', 'given': 'B.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1984
Measurements were made of the lateral hydrodynamic forces experienced by a centrifugal pump impeller performing circular whirl motions within several volute geometries. Experiments were conducted for various flow coefficients, [phi], impeller rotating speeds or angular frequencies, w, and the angular frequency of the whirl motion, [omega], was varied from zero to nearly synchronous (equation) and to nearly antisynchronous (equation). The lateral forces were decomposed into (i) time averaged lateral forces and (ii) hydrodynamic force matrices representing the variation of the lateral forces with position of the impeller center. No assumptions concerning the form of these matrices need to be made. The latter can be further decomposed according to the variation with whirl frequency, the result being "stiffness", "damping", and "fluid inertial" rotordynamic force matrices. It was found that these force matrices essentially consist of equal diagonal terms and skew-symmetric off-diagonal terms. One consequence of this is that during its whirl motion the impeller experiences forces acting normal and tangential to the locus of whirl. Data on these normal and tangential forces are presented; in particular it is shown that there exists a region of positive reduced whirl frequencies, [omega/w], within which the hydrodynamic forces can be destabilizing with respect to whirl.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/98ds9-3jw38The Utilization of Specially Tailored Air Bubbles as Static Pressure Sensors in a Jet
https://resolver.caltech.edu/CaltechAUTHORS:OOIjfe84
Authors: {'items': [{'id': 'Ooi-K-K', 'name': {'family': 'Ooi', 'given': 'K. K.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1984
It is shown that air bubbles of a certain size may be used to measure the fluctuating pressure in a liquid jet. The conditions under which these bubbles accurately reflect the local static pressures are described in detail; the volume shape of the bubbles was determined by holography for a 3.17mm jet and the change in volume is interpreted as a result of the fluctuating pressure. The experimental results revealed that at any one instant, a wide spectrum of static pressure fluctuation intensities exist in the jet. It was also found that the probability distribution of these intensities has a slightly skewed bell shape distribution and that the fluctuating static pressure peaked at a higher positive value than a negative one.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vscq1-1mj67Forces on Centrifugal Pump Impellers
https://resolver.caltech.edu/CaltechAUTHORS:JERsips85
Authors: {'items': [{'id': 'Jery-B', 'name': {'family': 'Jery', 'given': 'Belgacem'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan'}}]}
Year: 1985
Forces are exerted on a centrifugal pump impeller, due to the asymmetry of the flow caused by the volute of diffuser, and to the motion of the center of the impeller whenever the shaft whirls. Recent work in the measurement of these forces as a function of the whirl speed to shaft speed ratio, and the influence of the volute, is reviewed. These forces may be decomposed into a steady force, a static stiffness matrix, a damping matrix and an inertia matrix. It is shown that for centrifugal pumps of the moderate specific speed typical of boiler feed stages, there is a region of potential shaft vibration excitation from the hydrodynamic forces if the operating speed is well above the first flexural critical speed.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/zexfq-97r37Experimental Measurements of Hydrodynamic Radial Forces and Stiffness Matrices for a Centrifugal Pump-Impeller
https://resolver.caltech.edu/CaltechAUTHORS:CHAjfe85
Authors: {'items': [{'id': 'Chamieh-D-S', 'name': {'family': 'Chamieh', 'given': 'Dmitri S.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1985
The present work is an experimental investigation of the possible forces of fluid dynamic origin that can act on a turbomachine rotor particularly when it is situated off its normal center position. An experimental facility, the Rotor Force Test Facility, has been designed and contructed in order to measure these kinds of forces acting on a centrifugal pump impeller when the latter is made to whirl in a slightly eccentric circular orbit. The scope of the present experimental work consists of measuring quasi-steady forces on the impeller as it whirls slowly about the axis of the pump rotation. These forces are due to interaction between the impeller and volute; they are decomposed into force components relative to the geometric center of the volute and to those proportional to displacent from this center. These latter are interpreted as stiffness matrices. Such matrices were obtained for two different volutes and both were found to be the sum of a diagonal and a skewsymmetric matrix. It can be shown that a stiffness matrix of this type can lead to dynamic instability of impeller shaft system in certain circumstances. This new experimental finding may explain some operational problems of "high-speed" hydraulic machinery. Comparison is made with various existing theoretical and experimental results.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/r8bv7-jtv92Analyses of the Characteristics of a Centrifugal Impeller with Leading Edge Cavitation by Mapping Methods
https://resolver.caltech.edu/CaltechAUTHORS:TSUjjmes86b
Authors: {'items': [{'id': 'Tsujimoto-Y', 'name': {'family': 'Tsujimoto', 'given': 'Yoshinobu'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}]}
Year: 1986
The characteristics of a centrifugal impeller under a condition with leading edge cavitation are analyzed by using conformal mapping methods. It is assumed that the thickness of the cavity is small, and linear cavity models are used. Concerning the treatment of the Bernoulli equation, two different models are considered. The first one is based on a full Bernoulli equation in a rotating frame. In the second model, the Bernoulli equation is linearized on the assumption that the disturbance due to cavity is small. The second model predicts shorter cavity, but the differences in the pressure distribution and in the head coefficient are small for the conditions with the same cavity length. The results of the first model are in general agreement with those by a singularity method and experiments.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ch642-gxn40A Theoretical Study of Impeller and/or Vaneless Diffuser Attributed Rotating Stalls and their Effects on the Whirling Instability of a Centrifugal Impeller
https://resolver.caltech.edu/CaltechAUTHORS:TSUjjmes86
Authors: {'items': [{'id': 'Tsujimoto-Y', 'name': {'family': 'Tsujimoto', 'given': 'Yoshinobu'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}]}
Year: 1986
Fluid forces on a centrifugal impeller rotating and whirling in a vaneless diffuser are analysed on the assumption of a two-dimensional inviscid flow. It is assumed that the number of impeller vanes is infinitely large and that the loss in the impeller can be estimated from the steady hydraulic and incidence losses taking into account the delay time of the loss. Further, the pressure at the outlet of the diffuser is assumed to be constant. On these assumptions impeller and/or diffuser attributed rotating stalls are observed, and the effects of parameters affecting the stalls are discussed. It is found that both stalls may cause the whirling instability of a centrifugal impeller.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/fw2g3-rj918Impeller Fluid Forces
https://resolver.caltech.edu/CaltechAUTHORS:BREaeopt86
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1986
This paper addresses the issue of the steady and unsteady forces which may be imparted to a pump impeller by the through flow. The historical trend to increase the power density and speed of turbomachines has inevitably led to an increase in the number of fluid/structure interaction problems because the fluid forces scale like the square of the speed and thus become increasingly important relative to the structural strength. The present paper focuses on the radial forces acting on the impeller of a pump. Under the sponsorship of NASA, the authors have, over the past few years, conducted an extensive investigation of these forces and the associated hydrodynamically induced rotordynamic coefficients. A new facility, called the Rotor Force Test Facility was designed and constructed for the experimental component of this program. Measurements of the forces and rotordynamic coefficients have been made for a range of different impeller and volutes and include tests with the impeller of the high pressure oxygen turbopump (HPOTP) in the Space Shuttle Main Engine. Furthermore, tests have been conducted with different leakage flow geometries and, with different levels of pump cavitation. The paper will summarize these experimental measurements and the results of some theoretical analyses.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/q09wm-syv05On the Effect of Cavitation on the Radial Forces and Hydrodynamic Stiffness of a Centrifugal Pump
https://resolver.caltech.edu/CaltechAUTHORS:FRAriphpt86
Authors: {'items': [{'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1986
The asymmetric flow within a volute exerts a radial force on a centrifugal impeller. The present paper presents experimental measurements of the radial forces on the impeller in the presence of cavitation.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/2n8vk-2gq42Unsteady Diffuser Vane Pressure and Impeller Wake Measurements in a Centrifugal Pump
https://resolver.caltech.edu/CaltechAUTHORS:ARNcfm87
Authors: {'items': [{'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1987
Unsteady surface pressure measurements on a vaned diffuser of a centrifugal pump, and wake measurement of the flow exiting a centrifugal impeller into a vaneless diffuser are presented. Frequency spectra and ensemble averages are given for the unsteady measurements. Two different impellers were used, the pump impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine) and a two-dimensional impeller. The magnitude of the unsteady total pressure measured in the stationary frame at the impeller exit was found to be of the same order of magnitude as the total pressure rise across the pump. The magnitude of the unsteady diffuser vane pressures was observed to be significantly different on suction and pressure side of the vane, attaining its largest value on the suction side near the leading edge while decreasing along the vane.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/s5dc5-x4s59Rotordynamic Forces on Centrifugal Pump Impellers
https://resolver.caltech.edu/CaltechAUTHORS:FRAecfm87
Authors: {'items': [{'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R.'}}, {'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1987
The asymmetric flow around an impeller in a volute exerts a force upon the impeller. To study the rotordynamic force on an impeller which is vibrating around its machine axis of rotation, the impeller, mounted on a dynamometer, is made to whirl in a circular orbit within the volute. The measured force is expressed as the sum of a steady radial force and an unsteady force due to the eccentric motion of the impeller. These forces were measured in separate tests on a centrifugal pump with radically increased shroud clearance, a two-dimensional impeller, and an impeller with an inducer, the impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Enginer). In each case, a destabilizing force was observed over a region of positive whirl.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/pxvhr-7j996Linearized Dynamics of Two-Dimensional Bubbly and Cavitating Flows Over Slender Surfaces
https://resolver.caltech.edu/CaltechAUTHORS:DAGjfm88
Authors: {'items': [{'id': "d'Agostino-L", 'name': {'family': "d'Agostino", 'given': 'Luca'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}]}
Year: 1988
The present work investigates the dynamics of two-dimensional, steady bubbly flows over a surface and inside a symmetric channel with sinusoidal profiles. Bubble dynamics effects are included. The equations of motion for the average flow and the bubble radius are linearized and a closed-form solution is obtained. Energy dissipation due to viscous, thermal and liquid compressibility effects in the dynamics of the bubbles is included, while the relative motion of the two phases and viscous effects at the flow boundaries are neglected. The results are then generalized by means of Fourier synthesis to the case of surfaces with slender profiles of arbitrary shape. The flows display various flow regimes (subsonic, supersonic and superresonant) with different properties according to the value of the relevant flow parameters. Examples are discussed in order to show the effects of the inclusion of the various energy dissipation mechanisms on the flows subject to harmonic excitation. Finally the results for a flow over a surface with a Gaussian-shaped bump are presented and the most important limitations of the theory are briefly discussed.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/knghh-q2q23Rotor-Stator Interaction in a Diffuser Pump
https://resolver.caltech.edu/CaltechAUTHORS:20120105-105138689
Authors: {'items': [{'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1988
The interaction between impeller blades and diffuser vanes in a diffuser
pump was investigated. Steady and unsteady pressure measurements were
taken on the diffuser vanes, and the shroud wall of a vaned and a vane less
diffuser. Steady, unsteady, and ensemble averaged unsteady data, as well as
frequency spectra are presented. The measurements were made for different
flow coefficients, shaft speeds, and radial gaps between impeller blade
trailing and diffuser vane leading edge (1.5% and 4.5% based on impeller
discharge radius). The resulting lift on the vane, both steady and unsteady,
was computed from the pressure measurements at mid vane height. The
magnitude of the fluctuating lift was found to be greater than the steady
lift. The pressure fluctuations were larger on the suction side than on the
pressure side attaining their maximum value, of the same order of magnitude
as the total pressure rise across the pump, near the leading edge. Pressure
fluctuations were also measured across the span of the vane. and those near
the shroud were significantly smaller than those near the hub. The pressure
fluctuations on the shroud wall itself were larger for the vaned diffuser than
a vaneless diffuser. Lift, vane pressure, and shroud wall pressure fluctuations
decreased strongly with increasing radial gap.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/b7b9d-afg79Theoretical Study of Fluid Forces on a Centrifugal Impeller Rotating and Whirling in a Volute
https://resolver.caltech.edu/CaltechAUTHORS:TSUjvasrd88
Authors: {'items': [{'id': 'Tsujimoto-Y', 'name': {'family': 'Tsujimoto', 'given': 'Y.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}]}
Year: 1988
Fluid forces on a rotating and whirling centrifugal impeller in a volute are analyzed with the assumption of a two-dimensional rotational, inviscid flow. For simplicity, the flow is assumed to be perfectly guided by the impeller vanes. The theory predicts the tangential and the radial force on the whirling impeller as functions of impeller geometry, volute spacing, and whirl ratio. A good qualitative agreement with experiment is found.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/jff4r-nk048Experimental Investigation of Rotor-Stator Interaction in a Centrifugal Pump with Several Vaned Diffusers
https://resolver.caltech.edu/CaltechAUTHORS:ARNjt90
Authors: {'items': [{'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1989
DOI: 10.1115/89-GT-62
This paper describes an experimental investigation of rotor-stator interaction in a centrifugal pump with several vaned diffusers. Steady and unsteady diffuser vane pressure measurements were made for a two-dimensional test impeller. Unsteady impeller blade pressure measurements were made for a second two-dimensional impeller with blade number and blade geometry identical to the two-dimensional impeller used for the diffuser vane pressure measurements. The experiments were conducted for different flow coefficients and differeent radial gaps between the impeller blade trailing edge and the diffuser vane leading edge (5 and 8 percent of the impeller discharge radius). The largest pressure fluctuations on the diffuser vanes and the impeller blades were found to be of the same order of magnitude as the total pressure rise across the pump. The largest pressure fluctuations on the diffuser vanes were observed to occur on the suction side of the vane near the vane leading edge, whereas on the impeller blades the largest fluctuations were observed to occur at the blade trailing edge. However, the dependence of the fluctuations on the flow coefficient was found to be different for te diffuser vanes and the impeller blades; on the vane suction side, the fluctuations were largest for the maximum flow coefficient and decreased with decreasing flow coefficient, whereas at the blade trailing edge, the fluctuations were smallest for the maximum flow coefficient and increased with decreasing flow coefficient. Increasing the number of the diffuser vanes resulted in a significant decrease of the impeller blade pressure fluctuations. The resulting lift on the diffuser vanes was computed from the vane pressure measurements; the magnitude of the fluctuating lift was found to be larger than the steady lift.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vgx0t-j5982The Rotordynamic Forces on a Centrifugal Pump Impeller in the Presence of Cavitation
https://resolver.caltech.edu/CaltechAUTHORS:FRAasmespm89
Authors: {'items': [{'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1989
An experiment in forced vibration was conducted to study the fluid-induced rotordynamic force on an impeller whirling along a trajectory eccentric to its undeflected position. The prescribed whirl trajectory of the rotor is a circular orbit of a fixed radius. The force measured is a combination of a steady radial force due to volute asymmetries and an unsteady force due to the eccentric motion of the rotor. These measurements have been conducted over a full range of whirl/impeller speed ratios at different flow coefficients for various turbomachines. A destabilizing force was observed over a region of positive whirl ratio. The range of flow conditions examined for a centrifugal impeller in a spiral volute has been enlarged to include cavitation. Compared to the non-cavitating condition, cavitation corresponding to a head loss of three percent did not have a significant effect upon the unsteady force.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/pgt78-e7933Rotor-Stator Interaction in a Diffuser Pump
https://resolver.caltech.edu/CaltechAUTHORS:ARNjt89
Authors: {'items': [{'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1989
The interatction between impeller blades and diffuser vanes in a diffuser pump was investigated. Steady and unsteady pressure measurements were taken on the diffuser vanes, and the shroud wall of a vaned and a vaneless diffuser. Steady, unsteady, and ensemble-averaged unsteady data, as well as frequency spectra, are presented. The measurements were made for different flow coefficients, shaft speeds, and radial gaps between impeller blade trailing and diffuser vane leading edge (1.5 and 4.5 percent based on impeller discharge radius). The resulting lift on the vane, both steady and unsteady, was computed from the pressure measurements at midvane height. The magnitude of the fluctuating lift was found to be greater than the steady lift. The pressure fluctuations were larger on the suction side than on the pressure side attaining their maximum value, of the same order of magnitude as the total pressure rise across the pump, near the leading edge. Pressure fluctuations were also measured across the span of the vane, and those near the shroud were significantly smaller than those near the hub. The pressure fluctuations on the shroud wall itself were larger for the vaned diffuser than a vaneless diffuser. Lift, vane pressure, and shroud wall pressure fluctuations decreased strongly with increasing radial gap.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/cqdnd-e7820Impeller-Induced Rotor-Dynamic Forces
https://resolver.caltech.edu/CaltechAUTHORS:BREkfe89
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1989
The flow through and around the rotor of a turbomachine exerts a force on the rotor and, hence, rotor shaft and bearing system. In some circumstances this force may lead to excitation of shaft whirl in the direction of impeller rotation. Recent international research of this phenomenon is briefly reviewed; these findings suggest that turbomachines intended to operate well above the first critical speed should take the effect into account.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/whec1-45a43Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:GUIaetopt90
Authors: {'items': [{'id': 'Guinzburg-A', 'name': {'family': 'Guinzburg', 'given': 'A.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1990
This paper reviews the current state of knowledge of rotordynamic forces caused by the discharge-to-suction leakage flows in centrifugal pumps. The indications that these flows could contribute significantly to the rotordynamics motivated the fabrication of an experiment in which measurements of rotordynamic forces would be made on simulated leakage flows in which the flow rate, clearance, eccentricity and other parameters would be exercised in order to understand the phenomena. Sample data is presented and demonstrates substantial rotordynamic effects which could be potentially destabilizing. The rotordynamic forces appear to be inversely propertional to the clearance and change significant with the flow rate.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/p813q-r5738Measurements for the rotordynamic shroud forces for centrifugal pumps
https://resolver.caltech.edu/CaltechAUTHORS:GUI108
Authors: {'items': [{'id': 'Guinzburg-A', 'name': {'family': 'Guinzburg', 'given': 'A.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1990
An experiment was designed to measure the rotordynamic shroud forces on a centrigual pump impeller. The measurements were doen for various whirl/impeller ratios and for different flow rates. A destabilising tangential force was measured for small positive whirl ratios and this force decreased with increasing flow rate.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vffkf-r3c21Experimental Investigation of Rotor-Stator Interaction in a Centrifugal Pump With Several Vaned Diffusers
https://resolver.caltech.edu/CaltechAUTHORS:20190430-071649857
Authors: {'items': [{'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1990
DOI: 10.1115/1.2927428
This paper describes an experimental investigation of rotor-stator interaction in a centrifugal pump with several vaned diffusers. Steady and unsteady diffuser vane pressure measurements were made for a two-dimensional test impeller. Unsteady impeller blade pressure measurements were made for a second two-dimensional impeller with blade number and blade geometry identical to the two-dimensional impeller used for the diffuser vane pressure measurements. The experiments were conducted for different flow coefficients and different radial gaps between the impeller blade trailing edge and the diffuser vane leading edge (5 and 8 percent of the impeller discharge radius). The largest pressure fluctuations on the diffuser vanes and the impeller blades were found to be of the same order of magnitude as the total pressure rise across the pump. The largest pressure fluctuations on the diffuser vanes were observed to occur on the suction side of the vane near the vane leading edge, whereas on the impeller blades the largest fluctuations were observed to occur at the blade trailing edge. However, the dependence of the fluctuations on the flow coefficient was found to be different for the diffuser vanes and the impeller blades; on the vane suction side, the fluctuations were largest for the maximum flow coefficient and decreased with decreasing flow coefficient, whereas at the blade trailing edge, the fluctuations were smallest for the maximum flow coefficient and increased with decreasing flow coefficient. Increasing the number of the diffuser vanes resulted in a significant decrease of the impeller blade pressure fluctuations. The resulting lift on the diffuser vanes was computed from the vane pressure measurements; the magnitude of the fluctuating lift was found to be larger than the steady lift.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/tfa1z-5d972Observations of Cavitation on a Three-Dimensional Oscillating Hydrofoil
https://resolver.caltech.edu/CaltechAUTHORS:HARasmecmff90
Authors: {'items': [{'id': 'Hart-D-P', 'name': {'family': 'Hart', 'given': 'D. P.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1990
A test apparatus was designed and constructed to observe the effect of sinusoidal pitching oscillations on the cavitation of three-dimensional hydrofoils. The apparatus is capable of oscillating hydrofoils at a rate up to 50 Hz and provides for adjustments in oscillation amplitude and mean angle of attack. Observations of the effect of pitching oscillation on cavitation have been made for a NACA 64-309 (modified) hydrofoil operating at its designed mean angle of attack of 7 degrees with an oscillation amplitude of 2 degrees. Photographs illustrating the interaction between natural cavity shedding frequencies and the foil reduced frequency are included.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9snm4-y9p66The Rotordynamic Forces on a Centrifugal Pump Impeller in the Presence of Cavitation
https://resolver.caltech.edu/CaltechAUTHORS:FRAjfe90
Authors: {'items': [{'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1990
An experiment in forced vabration was conducted to study the fluid-induced rotordynamic force on an impeller whirling along a trajectory eccentric to its undeflected position in the presence of cavitation. The prescribed whirl trajectory of the rotor is a circular orbit of a fixed radius. The force measured is a combination of a steady radial force due to volute asymmetries and an unsteady force due to the eccentric motion of the rotor. These measurements have been conducted over a full range of whirl/impeller speed ratios at different flow coefficients without cavitation for various turbomachines. A destabilizing force was observed over a region of positive whirl ratio. The range of flow conditions examined for a centrifugal impeller in a spiral volute has been enlarged to include cavitation. Compared to the non-cavitating condition, cavitation corresponding to a head loss of three percent did not have a significant effect upon the unsteady force. However, a lesser degree of cavitation at the design point increased the destabilizing force for a particular set of whirl ratios.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/y12xr-11e20A Cavitation Susceptibility Meter with Optical Cavitation Monitoring -- Part Two: Experimental Apparatus and Results
https://resolver.caltech.edu/CaltechAUTHORS:DAGjfe91b.839
Authors: {'items': [{'id': "d'Agostino-L", 'name': {'family': "d'Agostino", 'given': 'L.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1991
This work in concerned with the development and operation of a Cavitation Susceptibility Meter based on the use of a venturi tube for the measurement of the active cavitation nuclei concentration in water samples as a function of the applied tension. The pressure at the venturi throat is determined from the upstream pressure and the local flow velocity without corrections for viscous effects because the flow possesses a laminar potential core in all operational conditions. The detection of cavitation and the measurement of the flow velocity are carried out optically by means of a Laser Doppler Velocimeter. A custom-made electronic Signal Processor is used for real time data generation and temporary storage and a computerized system for final data acquisition and reduction. The implementation of the whole system is described and the results of the application of the Cavitation Susceptibility Meter to the measurement of the water quality of tap water samples are presented and critically discussed with reference to the current state of knowledge on cavitation inception.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/m5ws3-whz90A Cavitation Susceptability Meter with Optical Cavitation Monitoring-Part One: Design Concepts
https://resolver.caltech.edu/CaltechAUTHORS:DAGjfe91a.836
Authors: {'items': [{'id': "d'Agostino-L", 'name': {'family': "d'Agostino", 'given': 'L.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1991
This work is concerned with the design of a Cavitation Susceptibility Meter based on the use of a venturi tube for the measurement of the active cavitation nuclei concentration in water samples as a function of the applied tension. The operation of the Cavitation Susceptibility Meter is analyzed and the main considerations leading to the proposed design are illustrated and critically discussed. The results of this analysis indicate that the operational range is mainly limited by nuclei interference, flow separation and saturation (choking), and suggest to develop a Cavitation Susceptibility Meter where; (1) the flow possesses a laminar potential core throughout the venturi throat section in all operational conditions; (b) the pressure at the venturi throat is determined from the upstream pressure and the local flow velocity; (c) the detection of cavitation and the measurement of the flow velocity are carried out optically by means of a Laser Doppler Velocimeter; (d) a custom-made electronic Signal Processor incorporating a frequency counter is used for real time data generation and temporary storage; (e) a computerized system performs the final acquisition and reduction of the data.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/75pcv-few66Separation and Surface Nuclei Effects in a Cavitation Susceptibility Meter
https://resolver.caltech.edu/CaltechAUTHORS:DAGjfe91c.840
Authors: {'items': [{'id': "d'Agostino-L", 'name': {'family': "d'Agostino", 'given': 'L.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1991
This work is concerned with the effects of flow separation and surface nuclei on the operation of a fixed geometry Cavitation Susceptibility Meter (CSM) with laminar flow. Cavitation is induced under controlled conditions at the throat of a glass venturi tube for the measurement of the active nuclei concentration in water samples as a function of the applied tension. Both cavitation and flow velocity are monitored optically by a Laser Doppler Velocimeter. The throat pressure is determined indirectly from the upstream pressure and the local flow velocity. The results show that laminar flow separation and surface nuclei effects are the most stringent operational limitations. Separation in the diffuser increases the minimum attainable throat pressure above the susceptibility of most cavitation nuclei commonly found in technical waters. Surface nuclei can generate extensive sheet or spot cavitation at relatively high tensions even on optically finished glass surfaces. These phenomena are difficult to eliminate and bring therefore into question the practical utility of CSM's with laminar flow and fixed geometry for the measurement of the dependence of the cavitating nuclei concentration over wide ranges of the applied tension, as required for cavitation studies.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0nyn4-htb29The Effect of Inlet Swirl on the Rotordynamic Shroud
Forces in a Centrifugal Pump
https://resolver.caltech.edu/CaltechAUTHORS:20120105-103828941
Authors: {'items': [{'id': 'Guinzburg-A', 'name': {'family': 'Guinzburg', 'given': 'A.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1992
The role played by fluid forces in determining the
rotordynamic stability of a centrifugal pump is gaining
increasing attention. The present research investigates
the contributions to the rotordynamic forces from the
discharge-to-suction leakage flows between the front
shroud of the rotating impeller and the stationary pump
casing. In particular, the dependency of the rotordynamic
characteristics of leakage flows on the swirl at the inlet to
the leakage path was examined . An inlet guide vane was
designed for the experiment so that swirl could be
introduced at the leakage flow inlet. The data demonstrates
substantial rotordynamic effects and a destabilizing
tangential force for small positive whirl ratios; this force
decreased with increasing flow rate. The effect of swirl on
the rotordynamic forces was found to be destabilizing.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/85v3n-bq611The Influence of Swirl Brakes on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:SIVfed93
Authors: {'items': [{'id': 'Sivo-J-M', 'name': {'family': 'Sivo', 'given': 'Joseph M.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1993
Increasing interest has been give to swirl brakes as a means of reducing destabilizing rotordynamic forces due to leakage flows in new high speed rocket turbopumps. Although swirl brakes have been used successfully in practice (such as with the Space Shuttle HPOTP), no experimental test until now have been performed to demonstrate their beneficial effect over a range of leakage flow rates. The present study investigates the effect of swirl brakes on rotordynamic forces generated by discharge-to-suction leakage flows in the annulus of shrouded centrifugal pumps over a range of subsynchronous whirl ratios and various leakage flow rates. In addition, the effectiveness of swirl brakes in the presence of leakage inlet (pump discharge) swirl is also demonstrated. The experimental data demonstrates that with the addition of swirl brakes a significant reduction in the destabilizing tangential force for lower flow rates is achieved. At higher flow rates, the brakes are detrimental. In the presence of leakage inlet swirl, brakes were effective over all leakage flow rates tested in reducing the range of whirl frequency ratio for which the tangential force is destabilizing.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9a2zk-4np65Observations on Off-Design Flows in Non-Cavitating Axial Flow Inducers
https://resolver.caltech.edu/CaltechAUTHORS:BHAfed93
Authors: {'items': [{'id': 'Bhattacharyya-A', 'name': {'family': 'Bhattacharyya', 'given': 'Abhijit'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1993
This paper describes an investigation of the flows in unshrouded and shrouded inducers which are known to be highly complex, three dimensional flows with real fluid effects. A flow visualization technique using tufts and paint dots was used to study the flows on the blade, hub and housing at off-design flows. It was found that the blade boundary layer flows were attached to the blade surface and that leakage flows were the cause of the upstream swirling backflow in unshrouded inducers. It was also found that shrouded inducers showed flow reversal near the leading edge in addition to the discharge-to-suction leakage flow. The observations provide a better understanding of the internal flows and the occurrence of upstream backflows.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/zev64-8qz94The Influence of Swirl Brakes and a Tip Discharge Orifice on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Shrouded Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:SIVcfdarp93
Authors: {'items': [{'id': 'Sivo-J-M', 'name': {'family': 'Sivo', 'given': 'J. M.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1993
Recent experiments conducted in the Rotor Force Test Facility at the California Institute of Technology have examined the effects of a tip leakage restriction and swirl brakes on the rotordynamic forces due to leakage flows on an impeller undergoing a prescribed circular whirl. The experiments simulate the leakage flow conditions and geometry of the Alternate Turbopump Design (ATD) of the Space Shuttle High Pressure Oxygen Turbopump and are critical to evaluating the pump's rotordynamic instability problems. Previous experimental and analytical results have shown that discharge-to-suction leakage flows in the annulus of a shrouded centrifugal pump contribute substantially to the fluid induced rotordynamic forces. Also, previous experiments have shown that leakage inlet (pump discharge) swirl can increase the cross-coupled stiffness coefficient and hence increase the range of positive whirl for which the tangential force is destabilizing. In recent experimental work, the present authors demonstrated that when the swirl velocity within the leakage path is reduced by the introduction of ribs or swirl brakes, then a substantial decrease in both the destabilizing normal and tangential forces could be achieved. Motivation for the present research is that previous experiments have shown that restrictions such as wear rings or orifices at pump inlets affect the leakage forces. Recent pump designs such as the Space Shuttle Alternate Turbopump Design (ATD) utilize tip orifices at discharge for the purpose of establishing axial thrust balance. The ATD has experienced rotordynamic instability problems and one may surmise that these tip discharge orifices may also have an important effect on the normal and tangential forces in the plane of impeller rotation. The present study determines if such tip leakage restrictions contribute to undesirable rotordynamic forces. Additional motivation for the present study is that the widening of the leakage path annular clearance and the installation of swirl brakes in the ATD has been proposed to solve its instability problems. The present study assesses the effect of such a design modification on the rotordynamic forces. The experimental apparatus consists of a solid or dummy impeller, a housing instrumented for pressure measurements, a rotating dynamometer and an eccentric whirl mechanism. The solid impeller is used so that leakage flow contributions to the forces are measured, but the main throughflow contributions are not experienced. The inner surface of the housing has been modified to accommodate meridional ribs or swirl brakes within the leakage annulus. In addition, the housing has been modified to accommodate a discharge orifice that qualitatively simulates one side of the balance piston orifice of the Space Shuttle ATD. Results indicate the detrimental effects of a discharge orifice and the beneficial effects of brakes. Plots of the tangential and normal forces versus whirl ratio show a substantial increase in these forces along with destabilizing resonances at some positive whirl ratios when a discharge orifice is added. When brakes are added, some of the detrimental effects of the orifice are reduced. For the tangential force, a plot versus whirl ratio shows a significant reduction and a destabilizing resonance appears to be eliminated. For the normal force, although the overall force is not reduced, again a destabilizing resonance appears to be eliminated.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rhnxr-mcz84The Effect of Inlet Swirl on the Rotordynamic Shroud Forces in a Centrifugal Pump
https://resolver.caltech.edu/CaltechAUTHORS:GUIjegtp93
Authors: {'items': [{'id': 'Guinzburg-A', 'name': {'family': 'Guinzburg', 'given': 'A.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1993
The role played by fluid forces in determining the rotordynamic stability of a centrifugal pump is gaining increasing attention. The present research investigates the contributions to the rotordynamic forces from the discharge-to-suction leakage flows between the front shroud of the rotating impeller and the stationary pump casing. In particular, the dependency of the rotordynamic characteristics of leakage flows on the swirl at the inlet to the leakage path was examined. An inlet guide vane was designed for the experiment so that swirl could be introduced at the leakage flow inlet. The data demonstrate substantial rotordynamic effects and a destabilizing tangential force for small positive whirl ratios: this force decreased with increasing flow rate. The effect of swirl on the rotordynamic forces was found to be destabilizing.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qeykk-0dd18Rotordynamic Forces in Cavitating Inducers
https://resolver.caltech.edu/CaltechAUTHORS:BHAfed94
Authors: {'items': [{'id': 'Bhattacharyya-A', 'name': {'family': 'Bhattacharyya', 'given': 'Abhijit'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1994
This paper reports an experimental investigation of the rotordynamic forces that occur in a whirling three bladed inducer under the influence of cavitation. The effect of lowering the flow coefficient (and thus causing reverse flows) on these forces were also investigated. The results show the occurrence of large destabilizing peaks in the force tangential to the whirl orbit for positive whirl frequency ratios. Cavitation caused these forces to become destabilizing at both negative and positive whirl frequency ratios. The magnitude of the destabilizing forces increased with decreasing vacitation numbers and flow coefficient. The rotordynamic data obtained do not exhibit the kind of quadratic functional behavior which is normally ussumed in many rotordynamic models. Consequently the conventional generalized stiffness, damping and interia matrices cannot be determined for the inducer. The results demonstrate the complexity of rotordynamic forces and their consequences on stability of axial flow inducers.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/a9j98-a1r67Laser Velocimeter Measurements in the Leakage Annulus of a Whirling Shrouded Centrifugal Pump
https://resolver.caltech.edu/CaltechAUTHORS:SIVasla94
Authors: {'items': [{'id': 'Sivo-J-M', 'name': {'family': 'Sivo', 'given': 'J. M.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}, {'id': 'Ferguson-T-V', 'name': {'family': 'Ferguson', 'given': 'T. V.'}}, {'id': 'Lee-G-A', 'name': {'family': 'Lee', 'given': 'G. A.'}}]}
Year: 1994
Previous experiments conducted in the Rotor Force Test Facility at the California Institute of Technology have thoroughly examined the effect of leakage flows on the rotordynamic forces on a centrifugal pump impeller undergoing a prescribed circular whirl. These leakage flows have been shown to contribute substantially to the total fluid induced forces acting on a pump. However, to date nothing is known of the flow field in the leakage annulus of shrouded centrifugal pumps. No attempt has been made to qualitatively or quantitatively examine the velocity field in the leakage annulus. Hence the test objective of this experiment is to acquire fluid velocity data for a geometry representative of the leakage annulus of a shrouded centrifugal pump while the rotor is whirling using laser velocimetry. Tests are performed over a range of whirl ratios and a flowrate typical of Space Shuttle Turbopump designs. In addition to a qualitive study of the flow field, the velocity data can be used to anchor flow models.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/fe7w3-44e64Experimental Results for the Rotordynamic Characteristics of Leakage Flows in Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:GUIjfme94
Authors: {'items': [{'id': 'Guinzburg-A', 'name': {'family': 'Guinzburg', 'given': 'A.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1994
In recent years, increasing attention has been give to fluid-structure interaction problems in turbomachines. The present research focuses on just one such fluid-structure interaction problem, namely, the role played by fluid forces in determining the rotordynamic stability and characteristics of a centrifugal pump. The emphasis of this study is to investigate the contributions to the rotordynamic forces from the discharge-to-suction leakage flows between the front shroud of the rotating impeller and the stationary pump casing. An experiment was designed to measure the rotordynamic shroud forces due to simulated leakage flows for different parameters such as flow rate, shroud clearance, face-seal clearance and eccentricity. The data demonstrate substantial rotordynamic effects and a destabilizing tangential force for small positive whirl frequency ratios; this force decreased with increasing flow rate. The rotordynamic forces appear to be inversely proportional to the clearance and change significantly with the flow rate. Two sets of data taken at different eccentricities yielded quite similar nondimensional rotordynamic forces indicating that the experiments lie within the linear regime of eccentricity.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/dweye-m5w71The Influence of Swirl Brakes and a Tip Discharge Orifice on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Shrouded Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:SIVtpdrm94
Authors: {'items': [{'id': 'Sivo-J-M', 'name': {'family': 'Sivo', 'given': 'J. M.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1994
This paper reports on experiments conducted in the Rotor Force Test Facility at the California Institute of Technology to examine the effects of a tip leakage restriction and swirl brakes on the rotordynamic forces due to leakage flows on an impeller undergoing a prescribed circular whirl. The experiments simulate the leakage flow conditions and geometry of the Alternate Turbopump Design (ATD) of the Space Shuttle High Pressure Oxygen Turbopump and are critical to evaluating the pump's instability problems.
Results indicate the detrimental effects of a discharge orifice and the beneficial effects of adding swirl brakes. Plots of the tangential and normal forces versus whirl frequency ratio show a substantial increase in these forces along with destabilizing resonances when a discharge orifice is added. When swirl brakes are added, some of the detrimental effects of the orifice are reduced. For the tangential force, a significant reduction occurs and a destabilizing resonance appears to be eliminated. For the normal force, although the overall force is not reduced, once again a destabilizing resonance appears to be eliminated.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/pcvwh-wn644The Influence of Swirl Brakes on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:SIVjfe95
Authors: {'items': [{'id': 'Sivo-J-M', 'name': {'family': 'Sivo', 'given': 'J. M.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1995
Increasing interest has been given to swirl brakes as a means of reducing destabilizing rotordynamic forces due to leakage flows in new high speed rocket turbopumps. Although swirl brakes have been used successfully in practice (such as with the Space Shuttle HPOTP), no experimental tests until now have been performed to demonstrate their beneficial effect over a range of leakage flow rates. The present study investigates the effect of swirl brakes on rotordynamic forces generated by discharge-to-suction leakage flows in the annulus of shrouded centrifugal pumps over a range of subsynchronous whirl rtios and various leakage flow rates. In addition, the effectiveness of swirl brakes in the presence of leakage inlet (pump discharge) swirl is also demonstrated. The experimental data demonstrates that with the addition of swirl brakes a significant reduction in the destabilizing tangential force for lower flow rates is achieved. At higher flow rates, the brakes are detrimental. In the presence of leakage inlet swirl, brakes were effective over all leakage flow rates tested in reducing the range of whirl frequency ratio for which the tangential force is destabilizing.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/7jg15-1xv39Rotordynamic Forces in Cavitating Inducers
https://resolver.caltech.edu/CaltechAUTHORS:BHAjfe97
Authors: {'items': [{'id': 'Bhattacharyya-A', 'name': {'family': 'Bhattacharyya', 'given': 'A.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1997
This paper reports an experimental investigation of rotordynamic forces in a whirling axial flow inducer under the influence of cavitation at various flow coefficients. The results show the occurrence of large destabilizing peaks in the force tagential to the whirl orbit for positive whirl frequency ratios. The magnitude of the destabilizing forces increased with a decrease in cavitation number and flow coefficient. The rotordynamic data obtained do not exhibit quadratic functional behavior normally assumed in many rotordynamic models. Consequently, conventional generalized stiffness, damping, and intertia matrices cannot be determined for the inducer. The results demonstrate the complexity of rotordynamic forces and their consequences on stability of axial flow inducers.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/46m20-qbx89Effects of Leading Edge Sweep on the Cavitating Characteristics of Inducer Pumps
https://resolver.caltech.edu/CaltechAUTHORS:ACOijrm01
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Tsujimoto-Y', 'name': {'family': 'Tsujimoto', 'given': 'Yoshinobu'}}, {'id': 'Yoshida-Y', 'name': {'family': 'Yoshida', 'given': 'Yoshiki'}}, {'id': 'Azuma-S', 'name': {'family': 'Azuma', 'given': 'Seiji'}}, {'id': 'Cooper-P', 'name': {'family': 'Cooper', 'given': 'Paul'}}]}
Year: 2001
DOI: 10.1155/S1023621X01000343
It is well known that leading edge sweep has a favorable effect on the cavitation of turbomachines. However, the mechanisms of the improvement have not been made clear. It has been shown that the lift and the drag on a cavitating swept single hydrofoil can be correlated fairly well based on the velocity component normal to the leading edge. In the present paper, such correlations for swept cascades are derived and the results are examined, neglecting the full geometrical effects of the inducer rotor. It is shown that the correlations can simulate the developments of various types of cavitation, including alternate blade cavitation, rotating cavitation, and cavitation surge. This result is based on the observation that the steady cavity length, as well as the developments of various types of cavitation, is fairly well predicted by the correlation.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/64sz4-nv989Panel Discussion on Inducer Design Criteria
https://resolver.caltech.edu/CaltechAUTHORS:WEGijrm03
Authors: {'items': [{'id': 'Wegner-M', 'name': {'family': 'Wegner', 'given': 'Marc'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Tsujimoto-Y', 'name': {'family': 'Tsujimoto', 'given': 'Yoshinobu'}}]}
Year: 2003
DOI: 10.1155/S1023621X03000204
This article reports a panel discussion titled Inducer Design Criteria presented at the 9th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC-9). The presentations of the panelists and the subsequent discussions are summarized. It is shown that cavitation instabilities are major problems in modern turbopumps and that design criteria to eliminate them are needed. Available design methods for inducers and marine propellers are reviewed, and new criteria to enhance stability are proposed. The current status of CFD is reviewed and an example of successful application is shown. Discussions of several specific topics are reported and future research needs are noted.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/xv56w-k2h84Fluid-induced Rotordynamic Forces and Instabilities
https://resolver.caltech.edu/CaltechAUTHORS:BRE225
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}]}
Year: 2006
DOI: 10.1002/stc.145
In the late 1970s, the authors began a collaboration with our colleague Tom Caughey that helped define a new set of fluid-structure interaction phenomena in turbomachines, namely fluid-induced rotordynamic forces and instabilities. That collaboration and the 31 joint ABC papers it produced epitomized Tom Caughey's genius and we reprise it here in his honor.
The design of the space shuttle main engine (SSME) pushed beyond the boundaries of many known technologies. In particular, the rotating speeds and operating conditions of the high speed liquid oxygen and liquid hydrogen turbopumps were extreme and early testing revealed a whirl instability whose magnitude exceeded expectations and allowable limits. It was suspected and later proven that fluid-induced rotordynamic effects were a contributing factor and yet very little was known of such phenomena. As one of the efforts seeking understanding, we constructed a facility to measure fluid-induced rotordynamic forces. This was subsequently used in a broad range of investigations. Initially, the effort was directed to understanding the source and parametric variations of destabilizing fluid forces. Later various components of the flow in a high speed turbopump were investigated. And finally, some ameliorative measures and their effectiveness were examined. This paper reviews this body of knowledge and the lessons learnt along the way.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/14nwq-zph10Microbubbles and Cavitation
https://resolver.caltech.edu/CaltechAUTHORS:20140509-155647418
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Katz-J', 'name': {'family': 'Katz', 'given': 'J.'}}, {'id': "O'Hern-T-J", 'name': {'family': "O'Hern", 'given': 'T. J.'}}]}
Year: 2014
The present report arose from a joint effort of the California Institute of Technology, The Catholic University of America and the David Taylor Naval Ship Research and Development Center. The initial purpose was to document by
both light-scattering and holographic techniques the distribution of microbubbles in laboratory cavitation test facilities (under different conditions of
cavitation testing), to compare these two different techniques where feasible and then, as the last stage, to make similar observations of nuclei in natural
or oceanic waters. It has been apparent to many workers in the field of cavitation inception that there has not yet been adequate correlation of laboratory and field conditions for cavitation testing - particularly for
cavitation inception testing. Thus the proposed work offered the first real opportunity to explore this important connection. Caltech's role in this work
was to design and build a holographic system that would be suitable for use either in the laboratory or the field. In the first case we anticipated making
laboratory nuclei observations in the Institute's Low Turbulence Water Tunnel (LTWT) jointly with the light-scattering device designed by Professor
S. C. Ling of C.U.A. and developed further by Mr. S. Gowing of DTNSRDC. For the latter case, the field work, it was proposed to install the holographic system in a submersible tank to permit holographic recordings of a suitable
test volume of fluid. As an initial goal a depth of 100 feet was selected for the maximum depth of operation.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/fy512-ax226A laboratory experiment on simulated wave-riding dolphins
https://resolver.caltech.edu/CaltechAUTHORS:20140611-100012389
Authors: {'items': [{'id': 'Perry-B', 'name': {'family': 'Perry', 'given': 'Byrne'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Kiceniuk-T', 'name': {'family': 'Kiceniuk', 'given': 'Taras'}}]}
Year: 2014
[no abstract]https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/34065-n0d14Laboratory Developments for Study of Flow in Rotating Channels
https://resolver.caltech.edu/CaltechAUTHORS:20140822-120905521
Authors: {'items': [{'id': 'Knapp-R-T', 'name': {'family': 'Knapp', 'given': 'R. T.'}}, {'id': 'Hollander-A', 'name': {'family': 'Hollander', 'given': 'A.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Osborne-W-C', 'name': {'family': 'Osborne', 'given': 'W. C.'}}]}
Year: 2014
[no abstract]https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/f1nm9-mxt76Note on the Application of Cascade Theory to Design of Axial-Flow Pumps
https://resolver.caltech.edu/CaltechAUTHORS:20140826-113516141
Authors: {'items': [{'id': 'Linhardt-H-D', 'name': {'family': 'Linhardt', 'given': 'H. D.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 2014
Theoretical and experimental results are presented which reassure the usefulness of two-dimensional cascade theories to the design of axial flow pumps. For this purpose it is necessary to include the effect of the blade thickness upon the impeller flow which has been found to be
responsible for reported discrepancies between predictions of thin airfoil theories and the performance of axial-flow pumps characterized by high stagger angle and low aspect ratio.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/aj78x-14728Experimental Study of Cavitating Hydrofoils in Cascade
https://resolver.caltech.edu/CaltechAUTHORS:20141014-162616524
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Wade-R-B', 'name': {'family': 'Wade', 'given': 'R. B.'}}]}
Year: 2014
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/mxmkf-19n05Report on Design and Construction of the Axial Flow Pump Test Facility
https://resolver.caltech.edu/CaltechAUTHORS:20150506-102839661
Authors: {'items': [{'id': 'Fuller-T-W', 'name': {'family': 'Fuller', 'given': 'T. W.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/8029r-mae79An Experimental Study of Axial Flow Pump Cavitation
https://resolver.caltech.edu/CaltechAUTHORS:20150506-152851465
Authors: {'items': [{'id': 'Guinard-P', 'name': {'family': 'Guinard', 'given': 'P.'}}, {'id': 'Fuller-T', 'name': {'family': 'Fuller', 'given': 'T.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/fxr2s-c1x60Cavitation in Axial Flow Pumps: Termination Report
https://resolver.caltech.edu/CaltechAUTHORS:20150529-142202908
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vdwsz-5qg65An Experimental and Theoretical Investigation of Two-Dimensional Centrifugal Pump Impellers
https://resolver.caltech.edu/CaltechAUTHORS:20150529-140358132
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/x2eed-0f630Selectively Ventilated Ring Wing Hydrofoils
https://resolver.caltech.edu/CaltechAUTHORS:20150603-114116510
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Wade-R-B', 'name': {'family': 'Wade', 'given': 'R. B.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/g98r1-0qm47An Experimental Study of Centrifugal Pump Impellers
https://resolver.caltech.edu/CaltechAUTHORS:20150603-111644987
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Bowerman-R-D', 'name': {'family': 'Bowerman', 'given': 'R. D.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/h33gr-62903Final Report: Hydrodynamics of Turbomachines
https://resolver.caltech.edu/CaltechAUTHORS:20150603-150220933
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/y7sf3-z0s93Linearized Theory of a Two-Dimensional Planing Flat Plate in a Channel of Finite Depth - I
https://resolver.caltech.edu/CaltechAUTHORS:20150604-164105273
Authors: {'items': [{'id': 'Ai-D-K', 'name': {'family': 'Ai', 'given': 'D. K.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Harrison-Z-L', 'name': {'family': 'Harrison', 'given': 'Z. L.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/7m4bb-cc523Cavitation Inception on the I.T.T.C. Standard Head Form
https://resolver.caltech.edu/CaltechAUTHORS:20150604-164453478
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Hamaguchi-H', 'name': {'family': 'Hamaguchi', 'given': 'H.'}}]}
Year: 2015
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.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qzw7f-r8a65Remarks on Cavitation in Turbomachines
https://resolver.caltech.edu/CaltechAUTHORS:20150604-163246659
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Hollander-A', 'name': {'family': 'Hollander', 'given': 'A.'}}]}
Year: 2015
Starting with the occurrence and discussion of the importance of cavitation in turbomachines, the development of the various stages of cavitation in a machine is reviewed, followed by a discussion of the various dimensionless parameters used to describe cavitating performance in a turbomachine. The calculations of optimum inlet diameter are carried out in terms of assumed acceptable cavitation parameters. Various methods of determining the minimum cavitation number before cavitation breakdown are explored, and a free streamline model of the flow in a simplified impeller is used to obtain theoretical estimates of the extent of cavitation as a function of blade geometry and angle of attack. Some recent work of the effect of the thermodynamic properties of the fluid on the cavitation performance is examined and the various assumptions used in these theories are criticized.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/66z01-3hm92