Article records
https://feeds.library.caltech.edu/people/Acosta-A-J/article.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenTue, 16 Apr 2024 13:15:24 +0000Effect 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.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.edu/records/sarzn-73h53The 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.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.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.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.edu/records/rwhkh-7kg58Some 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.edu/records/10js0-d3111Experimental 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.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.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.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.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.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.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.edu/records/46yee-8qk57Hydrofoils 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.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.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.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.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.edu/records/dyg8t-bqe22Unsteady 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.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.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.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.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.edu/records/abf38-myd50Observations 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.edu/records/yjtpj-gjn20The 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.edu/records/vscq1-1mj67Experimental 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.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.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.edu/records/fw2g3-rj918Linearized 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.edu/records/knghh-q2q23Theoretical 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.edu/records/jff4r-nk048Rotor-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.edu/records/cqdnd-e7820Experimental 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.edu/records/tfa1z-5d972The 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.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.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.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.edu/records/0nyn4-htb29The 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.edu/records/qeykk-0dd18Experimental 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.edu/records/dweye-m5w71The 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.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.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.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.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.edu/records/14nwq-zph10