bluuebunny/crossref_metadata_2025 huggingface dataset:
Drag Calculations for Vehicles in Very Long Tubes From Turbulent Flow Theory
Authors: Sud I. , Chaddock J. B.
Published: October 2009

Fundamental turbulent flow techniques are used to examine the annular fluid flow occurring in an idealized model of a high speed ground transportation system. The model consists of a smooth cylindrical train moving in an infinitely long tunnel, creating an annular gap with one wall in motion. The developing, and the fully developed, flow regions are separately analyzed by using fundamental relations of turbulent flow and Von Karman’s similarity hypothesis. The relevant equations are developed and numerical solution procedures presented. Limited sample calculations show good agreement with existing empirical and experimental results.
Instantaneous Pressure Distribution Around a Sphere in Unsteady Flow
Authors: Kovasznay L. S. G. , Tani I. , Kawamura M. , Fujita H.
Published: October 2009

Pressure fluctuations on a small sphere in a periodically pulsating jet are measured in relation to the study of measurements of instantaneous static pressure in unsteady flows, where the wavelength of unsteadiness is much longer than the probe dimensions and the amplitude of the velocity fluctuation is small. Both the instantaneous pressure on the sphere and the instantaneous velocity of the flow field in the absence of the sphere are measured by means of periodic sampling and averaging techniques. The measured surface pressure is expressed in terms of the measured velocity and acceleration of the flow. A simple inviscid theory is developed and compared with the experimental results. An application of the present results to the correct determination of instantaneous static pressure in unsteady flows is discussed.
Review—Basic Research Needs in Fluid Mechanics
Authors: Jones O. C. , Kreith F. , White F. M.
Published: October 2009

A small segment of the engineering community was surveyed to obtain their judgment regarding the long-range needs for basic research in fluid mechanics. This segment consisted of approximately 600 persons active in heat transfer and fluid mechanics committees within The American Society of Mechanical Engineers. Close to 200 persons responded giving useful information relating to needed research. Of the many topics identified, six generic areas stood out: turbulence; multiphase flows; fluid structure interactions; boundary layer effects; biological, geological, and environmental fluid flow; and the need for new facilities and improved instrumentation. These six areas were summarized and an initial estimate of the research priorities presented to the DOE-ESCOE workshop on Fluid Dynamics and Thermal Processes held at the University of Kentucky on February 1–2, 1979. The priorities were modified and the final results of the workshop included herein.
Correlations of Thermodynamic Effects for Developed Cavitation
Authors: Billet M. L. , Holl J. W. , Weir D. S.
Published: October 2009

The net positive suction head (NPSH) requirements for a pump are determined by the combined effects of cavitation, fluid properties, pump geometry, and pump operating point. An important part of this determination is the temperature depression (ΔT) defined as the difference between ambient liquid temperature and cavity temperature. Correlations are presented of the temperature depression for various degrees of developed cavitation on venturis and ogives. These correlations, based on a semiempirical entrainment theory, express ΔT in terms of the dimensionless numbers of Nusselt, Reynolds, Froude, Weber, and Pe´cle´t, and dimensionless cavity length (L/D). The ΔT data were obtained in Freon 114, hydrogen, and nitrogen for the venturis and in Freon 113 and water for the ogives.
Phase Distribution Mechanisms in Turbulent Two-Phase Flow in Channels of Arbitrary Cross Section
Authors: Drew D. A. , Lahey R. T.
Published: October 2009

An analytical model for the phase distribution mechanisms in fully developed turbulent two-phase flow in channels of arbitrary cross sections has been derived. The model has been applied to the special case of cylindrical pipe flow, and compared with existing data. It has been found that, for bubbly flow, it is the distribution of the liquid phase turbulence which determines the void distribution. Furthermore, the void distribution depends on the anisotropic nature of the turbulent two-phase flow.
A Four Hole Pressure Probe for Fluid Flow Measurements in Three Dimensions
Authors: Shepherd I. C.
Published: October 2009

A pressure probe which facilitates measurement of mean flow quantities in three dimensions simultaneously is described. Its main feature is a tip shaped like the frustrum of a pyramid, with three-side holes equispaced around a central hole. Flow quantities are related to the hole pressures by calibration, so that the tedious procedure of nulling or pressure balancing can be avoided. The advantages of this configuration over five-hole probes are that a simpler probe with a smaller head results, fewer pressures need to be recorded and because no redundant information is collected, determination of the dependent flow quantities is simpler and unambiguous.
A New Instrument in Cavitation Research: The Cavitation Susceptibility Meter
Authors: Oldenziel D. M.
Published: October 2009

The rate of cavitation in liquid flow appears to be linked to the concentration and size distribution of gas bubbles and “weak” nuclei in the liquid used, as well as to the dissolved gas content. Consequently, the onset of cavitation is related to the tensile strength of the liquid, rather than the vapor pressure. The tensile strength of the liquid depends on the amount of gas in gas pockets (i.e., gas bubbles and gas absorbed at solid particles) suspended in the liquid and the shape of these gas pockets. An instrument will be described, which measures the tensile strength in a direct way. In this method a sample of liquid is made to pass through a pressure well, the minimum pressure of which can be adjusted.
Equilibrium Parameters for Two-Dimensional Turbulent Wakes
Authors: Sreenivasan K. R. , Narasimha R.
Published: October 2009

The parameters characterizing a plane turbulent wake in its equilibrium state of development are determined through careful experiment and analysis.
An Analysis of Unsteady Torque on a Two-Dimensional Radial Impeller
Authors: Imaichi K. , Tsujimoto Y. , Yoshida Y.
Published: October 2009

Unsteady flows around radial impellers are analyzed by the use of singularity methods. Unsteady torque is given for transient and/or sinusoidal flow rate and/or angular velocity fluctuation. It is shown that the unsteady torque can be divided into three components—quasisteady, apparent mass and wake—and the nature of each component is discussed. As a result of separating the torque into these three components, it is shown that the wake component is usually smaller than the others. A gross estimate of torque fluctuation can be made easily by using the apparent mass coefficient given in the paper for logarithmic impellers covering a wide range of blade angles, blade numbers and impeller diameter ratios.
Compressor Stability Analysis
Authors: Baghdadi S. , Lueke J. E.
Published: October 2009

A Dynamic Compressor Analysis (DCA) applicable to axial flow compressors operating with a wide variety of inlet or exhaust conditions (steady-state or dynamic, and with total pressure and/or total temperature inlet distortion patterns) has been developed as part of the Air Force/DDA Contract “Effects of Inlet Temperature Distortion on Gas Turbine Engine Stability.” The analysis is described and analytical results are compared to data obtained during the test phase of the program. Included are clean inlet data, circumferential pressure and temperature inlet distortion data, combined circumferential temperature and pressure distortion data, and radial temperature distortion data. Both the analytically predicted interstage flow distributions and the compressor’s stability limits are compared to the test results, and are shown to be in close agreement.
Two-Way Coupling Effects in Dilute Gas-Particle Flows
Authors: Di Giacinto M. , Sabetta F. , Piva R.
Published: October 2009

A general analysis of gas-particle flows, under the hypotheses of number of particles large enough to consider the solid phase as a continuum and of volume fraction small enough to consider the suspension as dilute, is presented. The Stokes number Sk and the particle loading ratio β are shown to be the basic parameters governing the flow. Depending on the values of these two parameters, in one case the reciprocal interaction of the fluid and solid phases must be considered (two-way coupling), in the second case only the effect of the fluid field on the particle motion is relevant (one-way coupling). In the more general case of two-way coupling, the flow is governed by two sets of Navier-Stokes equations, one for each phase, which are coupled together through the particle volume fraction and the momentum interchange forces. The two systems of equations, expressed in the variables velocity, pressure, and particle volume fraction, are solved numerically by a finite difference scheme. The model has been applied to a duct with a sudden restriction, simulating a flow metering device. The coupling effect both on fluid and solid phase fields, the increase of pressure drop, and the energy dissipated in the fluid-solid interaction have been determined as functions of the governing parameters, Sk and β. The parametric study also indicates the ranges of β and Sk in which simplified formulations may be assumed.
The Structure of Turbulent Plane Couette Flow
Authors: El Telbany M. M. M. , Reynolds A. J.
Published: October 2009

Measurements of time-mean velocity, of longitudinal, normal and lateral velocity fluctuation intensities (u′, v′, w′) and of shear stress have been made for four cases of pure shear flow in a flat channel, one of whose walls is stationary while the second moves. Both walls are effectively smooth. General expressions for the mean velocity profile and a prediction of the friction coefficient are developed. Comparisons of the experimental results with existing data are made. The profiles of v′, w′, turbulence kinetic energy and production of turbulence energy across the channel are the first to be published.
On the Prediction of Swirling Flowfields Found in Axisymmetric Combustor Geometries
Authors: Rhode D. L. , Lilley D. G. , McLaughlin D. K.
Published: October 2009

Combustor modeling has reached the stage where the most useful research activities are likely to be on specific sub-problems of the general three-dimensional turbulent reacting flow problem. The present study is concerned with a timely fluid dynamic research task of interest to the combustor modeling community. Numerical computations have been undertaken for a basic two-dimensional axisymmetric flowfield which is similar to that found in a conventional gas turbine combustor. A swirling nonreacting flow enters a larger chamber via a sudden or gradual expansion. The calculation method includes a stairstep boundary representation of the expansion flow, a conventional k-ε turbulence model and realistic accommodation of swirl effects. The results include recirculation zone characterization and predicted mean streamline patterns. In addition, an experimental evaluation using flow visualization of neutrally-buoyant helium-filled soap bubbles is yielding very promising results. Successful outcomes of the work can be incorporated into the more combustion- and hardware-oriented activities of gas turbine engine manufacturers, including incorporating the modeling aspects into already existing comprehensive numerical solution procedures.
Discharge Coefficient for Venturi Flowmeter With Short Laying Length
Authors: Inoue Masahiro
Published: October 2009

This paper presents a method for predicting the discharge coeffcient for a venturi flowmeter with a short laying length where the static pressure is not uniform at the throat due to streamline curvature. The discharge coefficient is determined by combining potential flow calculations and one-dimensional viscous flow considerations. For the potential flow, an accurate computational technique proposed by the author is used to calculate the pressure at the throat tap by assuming that the total pressure is equal to the average one at the throat. The average total pressure is related to the inlet pressure by use of a generalized empirical equation based on one-dimensional considerations. Validity of the method is verified by comparison with published experimental data for short venturi flowmeters.
Development of Secondary Flow and Vorticity in Curved Ducts, Cascades, and Rotors, Including Effects of Viscosity and Rotation
Authors: Pouagare M. , Lakshminarayana B.
Published: October 2009

This paper is concerned with the numerical solution of the secondary vorticity equations in curved ducts, cascades, and rotors. The classical approach of splitting the flow into primary and secondary flow fields is employed and extended to include effects of viscosity, rotation, and density stratification. All elliptical effects are neglected and the Crank-Nicolson method is used to solve the secondary vorticity equation. The secondary flow field is obtained by solving a Poisson equation using a successive over-relaxation method. The results are compared with theoretical and experimental data from stationary ducts, compressor and turbine cascades. The agreement is good for most of the cases.
Interference Between Two Circular Cylinders of Finite Height Vertically Immersed in a Turbulent Boundary Layer
Authors: Taniguchi S. , Sakamoto H. , Arie M.
Published: October 2009

Measurements were made of the circumferential pressure distributions around two cylinders of finite height h and diameter d, spaced a distance s apart and vertically immersed in a turbulent boundary layer. The angle of attack φ and the dimensionless spacing s/d were varied. Drag and lift characteristics of both cylinders were classified into three regions divided by two zero-lift lines, namely 0 ≲ φ ≲ 30 deg, 30 ≲ φ ≲ 120 deg, and 120 ≲ φ ≲ 180 deg, in which interference between the two cylinders was found to be almost negligible for s/d ≳ 4.0, except for an influence in the wake region of the upstream cylinder.
New Skin Friction and Entrainment Correlations for Turbulent Boundary Layers
Authors: Ferziger J. H. , Lyrio A. A. , Bardina J. G.
Published: October 2009

A new correlation for the skin friction and two new correlations for the entrainment rate in turbulent boundary layers are presented. Relative to previous correlations, the new ones are at least as accurate, simpler to use, and applicable to separated flows.
Visualization Studies of a Shear Driven Three-Dimensional Recirculating Flow
Authors: Koseff J. R. , Street R. L.
Published: October 2009

A facility has been constructed to study shear-driven, recirculating flows. In this particular study, the circulation cell structure in the lid-driven cavity is studied as a function of the speed of the lid which provides the shearing force to a constant and uniform density fluid. The flow is three-dimensional and exhibits regions where Taylor-type instabilities and Taylor-Go¨rtler-like vortices are present. One main circulation cell and three secondary cells are present for the Reynolds number (based on cavity width and lid speed) range considered, viz., 1000–10000. The flows becomes turbulent at Reynolds numbers between 6000 to 8000. The transverse fluid motions (in the direction perpendicular to the lid motion) are significant. In spite of this, some key results from two-dimensional numerical simulations agree well with the results of the present cavity experiments.
Dynamics of Vertical Annular Liquid Jets
Authors: Esser P. D. , Abdel-Khalik S. I.
Published: October 2009

A theoretical model is developed to determine the flow characteristics for vertical liquid jets of annular cross section. The fully implicit numerical marching integration procedure is based on the parabolic flow theory of Patankar and Spalding. The method is more accurate and general than previous analytical models, since it accounts for all significant forces acting upon the jet and for complex boundary conditions, such as an ambient pressure difference across the jet or a non-uniform velocity profile at the inlet. Comparison of the results with existing experimental data indicates reasonable agreement, and the predictions correspond closely to those of the earlier theories for simplified flow cases.
Experiments on the Buckling of Thin Fluid Layers Undergoing End-Compression
Authors: Blake K. R. , Bejan A.
Published: October 2009

This paper reports a series of experiments concerning the buckling of a slender fluid layer in a state of longitudinal compression. The experiments consist of floating a layer of highly viscous oil on a pool of water and, manually, compressing the layer from the side. Photographs of the buckled layer show conclusively that the buckling wavelength is largely insensitive to either the rate of compression or the viscosity of the fluid layer. The observations suggest that the buckling wavelength is actually a characteristic length scale (a property) of the fluid layer, in contrast with the buckling theory of purely viscous layers (Buckmaster, Nachman, and Ting, [7]) where the buckling wavelength remains to be determined randomly by initial disturbances.
Theoretical Study on the Flow About Savonius Rotor
Authors: Ogawa Takenori
Published: October 2009

A method for the two-dimensional analysis of the separated flow about Savonius rotors is presented. Calculations are performed by combining the singularity method and the discrete vortex method. The method is applied to the simulation of flows about a stationary rotor and a rotating rotor. Moreover, torque and power coefficients are computed and compared with the experimental results presented by Sheldahl et al. Theoretical and experimental results agree well qualitatively.
Cavitation Damage in Polymer Aqueous Solutions
Authors: Shima A. , Tsujino T. , Nanjo H. , Miura N.
Published: October 2009

Cavitation damage tests in polymer solutions are made with a vibratory cavitation apparatus. It is possible for this device to suppress the degradation of polymer by ultrasonic cavitation. Polymer solutions used are 100 wppm, 500 wppm, and 1000 wppm solutions of Polyox. The weight loss in 100 wppm Polyox solution is larger than that in water, but in 500 wppm and 1000 wppm Polyox solutions the weight losses after 60 min exposure to cavitation are relatively small. It is indicated that the cavitation damage in polymer solutions is subject to the effective influence of elastic properties of liquids.
An Analytical Model for Prediction of Two-Phase (Noncondensable) Flow Pump Performance
Authors: Furuya Okitsugu
Published: October 2009

During operational transients or a hypothetical LOCA (loss of coolant accident) condition, the recirculating coolant of PWR (pressurized water reactor) may flash into steam due to a loss of line pressure. Under such two-phase flow conditions, it is well known that the recirculation pump becomes unable to generate the same head as that of the single-phase flow case. Similar situations also exist in oil well submersible pumps where a fair amount of gas is contained in oil. Based on the one dimensional control volume method, an analytical method has been developed to determine the performance of pumps operating under two-phase flow conditions. The analytical method has incorporated pump geometry, void fraction, flow slippage and flow regime into the basic formula, but neglected the compressibility and condensation effects. During the course of model development, it has been found that the head degradation is mainly caused by higher acceleration on liquid phase and deceleration on gas phase than in the case of single-phase flows. The numerical results for head degradations and torques obtained with the model favorably compared with the air/water two-phase flow test data of Babcock and Wilcox (1/3 scale) and Creare (1/20 scale) pumps.
An Investigation of High Performance, Short Thrust Augmenting Ejectors
Authors: Yang Tah-teh , Ntone Francois , Jiang Tong , Pitts D. R.
Published: October 2009

The design of air-to-air, thrust augmenting ejectors having short curved wall diffuses utilizing boundary layer control is discussed. The design is achieved by an inverse method which uses the vorticity at the diffuser inlet as a flow parameter in the analysis. Three diffusers having ejector length-to-mixing chamber diameter ratios of approximately 6:1 and mixing chamber inlet area-to-primary nozzle area ratios of 20:1 and 40:1 were designed and tested. A new high level of performance was analytically predicted and achieved experimentally. Comparisons between predicted and observed performances, velocity distributions and pressure distributions are presented.
Prediction of Turbulent Rough-Wall Skin Friction Using a Discrete Element Approach
Authors: Taylor R. P. , Coleman H. W. , Hodge B. K.
Published: October 2009

A discrete element model for turbulent flow over rough surfaces has been derived from basic principles. This formulation includes surface roughness form drag and blockage effects as a constituent part of the partial differential equations and does not rely on a single-length-scale concept such as equivalent sandgrain roughness. The roughness model includes the necessary empirical information on the interaction between three-dimensional roughness elements and the flow in a general way which does not require experimental data on each specific surface. This empirical input was determined using data from well-accepted experiments. Predictions using the model are compared with additional data for fully-developed and boundary layer flows. The predictions are shown to compare equally well with both transitionally rough and fully rough turbulent flows without modification of the roughness model.
The Fluid Dynamics of Safety Valve Vent Stacks
Authors: Samimy M. , Addy A. L.
Published: October 2009

The flow through a safety valve vent stack system has been modeled and analyzed theoretically and experimentally. The theoretical analysis is based on the well known Chapman-Korst base flow theory. The base flow model is augmented with an empirically determined recompression factor to improve agreement between the theoretical analysis and experimental results. A computer program has been developed to solve the equations and provide necessary information to designers.
Numerical Solution of Two-Dimensional Turbulent Separated Flows Using a Reynolds Stress Closure Model
Authors: Celenligil M. C. , Mellor G. L.
Published: October 2009

Turbulent boundary layer separation is studied using the turbulence closure model suggested by Mellor and Yamada. An explicit central finite-differencing scheme is used to solve the governing transport equations. Three flow problems are considered: separation on a flat surface, separation and reattachment over a backward-facing step, and turbulent free shear layer with streamwise curvature. In the problem of separation behind a backward-facing step, nearly cyclic vortex shedding is obtained whereas the other two problems are stationary. The computed results for both mean and turbulence quantities are in fairly good agreement with experimental data.
Unsteady Flow in a Porous Medium Between Two Infinite Parallel Plates in Relative Motion
Authors: Soundalgekar V. M. , Takhar H. S. , Singh M.
Published: October 2009

An approximate solution to the unsteady flow of a viscous incompressible fluid through a porous medium bounded by two infinite parallel plates, the lower one stationary and the upper one oscillating in its own plane, is presented here. Expressions for the transient velocity, the amplitude, the phase angle α and the skin-friction are derived and numerically calculated. It is observed that the amplitude increases with increasing σ, the permeability parameter, and ω, the frequency. Also, there is always a phase lead, and the phase angle α decreases with increasing σ.
On the Fragmentation of Drops
Authors: Tan M. J. , Bankoff S. G.
Published: October 2009

Fragmentation of mercury drops falling through a bubbly aqueous liquid by a pressure shock wave was investigated by means of a shock tube capable of operating at driver pressures up to 3 MPa. The responses to moderately strong shock waves (up to 1.7 MPa) were photographed by a high-speed camera at rates of up to 4400 frames per second. The results show the existence of a critical Weber number, (We)cr = 17, for drop fragmentation. Qualitative characterization of the shock-drop interactions for single mercury drops is provided.
Measurements of Turbulence Generated by 60 Percent Solid Perforated Plates
Authors: Checkel M. D.
Published: October 2009

Combustion experiments simulating spark-ignition engine conditions require generation and measurement of high intensity, rapidly decaying turbulence in a combustion test cell. Turbulence is generated by drawing various perforated plates across the test cell and is measured by hot-wire anemometry in the test cell and behind the same perforated plates in a steadily flowing wind tunnel. To correlate test cell and wind tunnel turbulence measurements, a simple statistical model of hot-wire anemometer response in turbulence with negligible mean flow is used. Good agreement between the two measurements tends to confirm the model for this case and demonstrates the value of perforated plate turbulence generators in producing controllable, measurable turbulence for confined combustion research.
Computation of Gas Flowfields in Supersonic Particle Probes
Authors: Forney L. J. , McGregor W. K. , Van Dyke D. B.
Published: October 2009

The results of computations to predict the properties of gas flowfields in supersonic particle probe inlets are presented. In particular, a supersonic gas impinging on a thin walled cylindrical probe aligned parallel to the freestream has been analyzed. Inviscid solutions are obtained by a slight variant to MacCormack’s time-dependent finite difference method. Imposing outflow boundary conditions of fixed static pressure at the probe outlet, linear extrapolation of remaining gas properties, and a reflection technique on the probe wall including the tip, reasonable agreement is demonstrated for the shock detachment distance, stagnation pressure loss and gas ingestion rate. With some spacial smoothing and initial conditions characteristic of gas properties back of the shock, the numerical method converged in reasonable computation times, yielding a shock thickness of 2.5 grid spacings with no oscillations near the shock front.
Mean Flow Characteristics of a Turbulent Offset Jet
Authors: Pelfrey J. R. R. , Liburdy J. A.
Published: October 2009

A detailed study of the mean flow characteristics of a turbulent offset jet is presented. The flow is characterized by a longitudinal variation of curvature, skewed impingement onto a flat surface, a recirculating region, and the development of a wall jet region. Flow structure is described in the preimpingement, recirculation and impingement regions. An interdependence is shown among the pressure differential across the jet, jet curvature and entrainment. The magnitude of the curvature strain rate is found to be significant and implies that this flow cannot be accurately modelled as a thin shear layer. The jet decay and spread rates are similar to those of a plane jet if appropriate curved coordinates are used. The extent of the impingement region is approximately 20 nozzle widths downstream, in agreement with previous studies.
The Functional Role of Wing Corrugations in Living Systems
Authors: Buckholz R. H.
Published: October 2009

Questions concerning the functional role of spanwise wing corrugation in living systems are experimentally investigated. Attention was initially directed to this problem by observation of the irregular shape of many insect wings as well as other studies indicating higher lift on these wings. First, a flow visualization scheme was used to observe and photograph streamlines around two different wing sections. One of these, a sheet metal model with geometry matching that of a butterfly wing, was studied at a chord Reynolds number of 1500 and at a Reynolds number of 80 based on corrugation depth. A steady-state recirculation region near the model leading edge was found, and the separated flow region above this recirculation zone formed a laminar reattachment to the model. A second thicker wing was corrugated on the upper surface. Closed streamlines inside these upper surface corrugations were photographed at Reynolds numbers of 8000 and 3800 based on chord length, and 200 and 90 based on corrugation depth. Reductions in pressures on the corrugated upper wing surface relative to a smooth upper wing surface were then measured.
Flow Around Two Elliptic Cylinders in Tandem Arrangement
Authors: Ota Terukazu , Nishiyama Hideya
Published: October 2009

Flow around two elliptic cylinders in tandem arrangement was experimentally investigated through measurements of the surface static pressure distribution and estimations of the flow parameters such as the drag, lift and moment coefficients. The elliptic cylinders examined had an axis ratio of 1:3 and they were aranged in tandem with an identical angle of attack. The angle of attack ranged from 0 to 90 deg and the nondimensional cylinder spacing l/c from 1.03 to 4.0, where l denotes the distance between the cylinder centers and c is the major axis. It has been found that the flow characteristics vary drastically with the angle of attack and also the cylinder spacing.
Analysis of Turbulent Flow Past a Class of Semi-Infinite Bodies
Authors: Abdelhalim A. M. , Ghia U. , Ghia K. N.
Published: October 2009

This study was undertaken with the primary purpose of developing an analysis for flow past a class of two-dimensional and axisymmetric semi-infinite bodies. The time-averaged Navier-Stokes equations for these flows are derived in surface-oriented conformal coordinates (ξ, η) in terms of similarity-type vorticity and stream-function variables. Turbulence closure is achieved by means of a two-equation turbulence model utilizing the kinetic energy k and its dissipation rate ε which enable determination of the isotropic eddy viscosity. The coupled vorticity and stream-function equations are solved simultaneously using an incremental formulation of the factored alternating-direction implicit scheme. The turbulence equations for k and ε are solved by the standard ADI method. Numerical solutions are obtained for the thin flat plate and compared with available experimental and analytical data. Also, results are obtained for flow over a parabola and compared with the flat-plate results in order to assess the effects of longitudinal curvature on the flow results. Finally, solutions are obtained for flow past a two-dimensional semi-infinite body with a shoulder, at Red = 24,000. The computed results have the same general trend as the experimental data; possible causes for the differences within the separated-flow region are cited.
Measurements of Wall Shear Stress in Axial Flow in a Square Lattice Rectangular Rod Bundle
Authors: Abdelghany M. , Eichhorn R.
Published: October 2009

Hot film probe measurements of the distribution of the wall shear stress were made for axial flow along a rectangular 3 × 6 array of rods with a pitch to diameter ratio, P/D = 4/3, and a wall to diameter ratio, W/D = 2/3. Measurements were performed on rods at several locations and on two duct side walls at a position 62 hydraulic diameters from the entrance. Local shear stress maxima occur near the largest subchannel flow areas with the lowest maximum local shear stress on rods nearest the sidewalls. Maximum to the minimum shear stress ratio on an individual rod is largest for the corner rod. Side wall maximum local shear stress occurs in the first wall subchannel. Overall friction factors calculated from the wall shear stress measurements agree with those calculated from pressure drop data.
Effect of a Vibrating Upstream Cylinder on a Stationary Downstream Cylinder
Authors: Moriya M. , Sakamoto H.
Published: October 2009

The flow around two circular cylinders in tandem arrangement in uniform flow where the upstream cylinder is forcibly vibrated in direction normal to the approach flow was experimentally studied at Reynolds number of 6.54 × 104. The spacing ratio 1/d (1: distance between centers of cylinders, d: diameter of circular cylinders) and the ratio of amplitude to cylinder diameter a/d (a: amplitude of transverse vibration of cylinder) were varied from 2 to 6 and 0 to 0.029 respectively. The effects of the vibration of the upstream cylinder on the downstream cylinder were discussed. In particular, two distinct “lock-in” regions were observed when the upstream cylinder was vibrated with a spacing ratio of 1/d = 3.0. The cylinder vibration was so effective even for a/d as small as 0.017 to cause two different flow patterns.
The Effects of Turbulence Stimulators on Cavitation Inception of Axisymmetric Headforms
Authors: Huang T. T.
Published: October 2009

Cavitation inception observations were made in the DTNSRDC 36-inch water tunnel on three axisymmetric headforms with and without various turbulence stimulators installed. Direct transition measurements, made on two of the headforms with and without distributed surface roughness, were found to correlate reasonably well with the computed spatial amplification factors, eN, at the separation locations. The computed eN factors were then used to estimate transition at other test conditions (without direct transition measurements). The predicted transition locations on all three smooth headforms occur at positions considerably aft of the minimum pressure locations. The three smooth headforms have different types of incipient cavitation—small band, transient spot, traveling bubble, and attached spot. The measured cavitation inception numbers for those cases are all significantly smaller than the computed negative values of the minimum pressure coefficient, −Cpmin. The predicted transition locations on the three headforms with densely and loosely packed 60-μm distributed roughness occur at a considerable distance upstream of the minimum pressure locations. Therefore, the flows over all three headforms with distributed roughness are turbulent at the Cpmin locations for the Reynolds numbers tested. Under this condition, the measured cavitation inception numbers are found to approximate well with the values of −Cpmin. The incipient cavitation is in the form of attached small bubble lines evenly distributed around the minimum pressure locations. The measured cavitation inception numbers for the three headforms with an isolated roughness band located upstream of the minimum pressure locations are found to approximate the computed values of −Cpmin when the roughness Reynolds number (Rk = ukK/ν) is equal to 600 and to be smaller than the values of −Cpmin when the value of Rk is less than 600. The incipient cavitation observed is attached patch type cavitation occurring in the vicinity of the minimum pressure location. The uncertainty of the measured cavitation inception numbers, in terms of the maximum deviations form the mean values of repeated measurements, is generally less than 0.02.
A Review of Holography Applications in Multiphase Flow Visualization Study
Authors: Lee Y. J. , Kim J. H.
Published: October 2009

Holographic techniques are used in many fields of science and engineering including flow observation. The purpose of this paper is to review applications of holography to multiphase flow study with emphasis on gas-solid and gas-liquid two-phase flows. The application of holography to multiphase flow has been actively explored in the areas of particle sizing in particulate flows and nuclei population measurements in cavitation study. It is also recognized that holography holds great potential as a means of visualizing dynamic situations inherent in multiphase flows. This potential has been demonstrated by holographic flow visualization studies of coal combustion processes in gas-solid flows, gas-liquid two-phase critical flow measurements, and flashing flows in a nozzle. More effective and refined holographic techniques as well as efficient image processing methods are very much in need to facilitate and enhance the understanding of complex physical phenomena occurring in multiphase flows.
Annular Cascade Testing of Turbine Nozzles at High Exit Mach Numbers
Authors: Williamson R. G. , Moustapha S. H.
Published: October 2009

This paper presents detailed information on the three-dimensional flow field in a realistic low aspect ratio, high turning nozzle vane design which incorporates end-wall contouring and which has been tested over a range of exit Mach number from subsonic up to the design value at mean section of 1.15. The experimental results, in the form of nozzle surface pressure distributions as well as surveys of pressure losses and flow angles at exit, are compared with those calculated by a three-dimensional flow analysis. The effects of exit Mach number on the measured nozzle performance are also presented.
Analysis of Normal Shock Waves in a Carbon Particle-Laden Oxygen Gas
Authors: Elperin I. , Igra O. , Ben-Dor G.
Published: October 2009

The propagation of a normal shock wave into a quiescent oxygen gas seeded with carbon particles is studied. Due to the elevated postshock temperature the carbon particles ignite and burn until they disappear. For evaluating the effect of the burning carbon particles on the postshock-wave flow field, i.e., the relaxation zone, the conservation equations for a steady one-dimensional reactive suspension flow are formulated and solved numerically. The solution was repeated for a similar inert suspension flow. Comparing the two solutions revealed that the carbon burning has a major effect on the suspension properties in the relaxation zone and on the eventually reached postshock equilibrium state. For example, much higher temperatures and velocities are obtained in the reactive suspension while the pressure is lower than in a similar inert case. Longer relaxation zones are obtained for the reactive suspension.
Parameters Affecting the Postshock Wave Relaxation Zone in an Oxygen Carbon Particle Suspension
Authors: Igra O. , Ben-Dor G. , Elperin I.
Published: October 2009

A parametric study was conducted regarding the effects of the initial carbon concentration, the initial carbon particle diameter, the shock wave Mach number and the preshock suspension pressure on the suspension behavior in the relaxation zone. The suspension was composed of oxygen gas seeded with small carbon particles. It was found that changing either the initial carbon concentration or the shock wave Mach number has a marked effect on the suspension behavior in the relaxation zone and on the eventually reached postshock equilibrium state. Changes in the initial carbon particle diameter (at a constant shock wave Mach number and carbon concentration) has no effect on the postshock equilibrium state, but it does affect the way in which the suspension reaches this equilibrium state. Changes in the preshock suspension pressure has only minor effects on the suspension behavior in the relaxation zone.
Contribution of Homogeneous Condensation Inside Cavitation Nuclei to Cavitation Inception
Authors: Matsumoto Y.
Published: October 2009

The response of a small gas bubble, so-called cavitation nucleus, to the reduction of ambient pressure is investigated theoretically and experimentally. Numerical results show that the gas mixture inside the bubble expands adiabatically and the temperature of the mixture decreases rapidly at the first stage, however the temperature recovers soon to the surrounding liquid temperature by homogeneous condensation which forms a mist inside the bubble. Consequently, the bubble grows almost isothermally. Experiments have been performed using a hydro-shock tube. The radius of a small bubble has been measured by a light-scattering method whose time resolving power is one micro-second. The experimental results are found to be in good agreement with the numerical results calculated using the ambient pressure change measured in the test section.
Bubble Dynamics and Cavitation Inception in Cavitation Susceptibility Meters
Authors: Chahine G. L. , Shen Y. T.
Published: October 2009

To improve the understanding of the scaling effects of nuclei on cavitation inception, bubble dynamics, multibubble interaction effects, and bubble-mean flow interaction in a venturi Cavitation Susceptibility Meter are considered theoretically. The results are compared with classical bubble static equilibrium predictions. In a parallel effort, cavitation susceptibility measurements of ocean and laboratory water were carried out using a venturi device. The measured cavitation inception indices were found to relate to the measured microbubble concentration. The relationship between the measured cavitation inception and bubble concentration and distribution can be explained by using the theoretical predictions. A tentative explanation is given for the observation that the number of cavitation bursting events measured by an acoustic device is sometimes an order of magnitude lower than the number of microbubbles measured by the light scattering detector. The questions addressed here add to the fundamental knowledge needed if the cavitation susceptibility meter is to be used effectively for the measurement of microbubble size distributions.
Pressure Recovery of Rotating Diffuser With Distorted Inflows
Authors: Kikuyama Koji , Murakami Mitsukiyo , Oda Shin-ichi , Gomi Ken-ichi
Published: October 2009

The pressure recovery and velocity distributions in a two-dimensional rotating curved diffuser have been studied experimentally when even and uneven flows, respectively, were introduced to the diffuser. Two types of uneven flow were adopted; one has a linear velocity gradient on the surface of revolution and the other a linear velocity gradient in the meridian plane. The pressure recovery in the diffuser is improved by the unformalizing process of the uneven inlet velocities in the downstream sections if larger velocities are in the suction side region, but it is deteriorated if larger velocities are introduced in the pressure side region. When an uneven flow with a velocity gradient in the meridian plane is introduced to the diffuser, increased rotation speed and the gradient of the inlet velocity profile deteriorate the pressure recovery.
Local Force Measurements on Finite-Span Cylinders in a Cross-Flow
Authors: Sin V. K. , So Ronald M. C.
Published: October 2009

A technique employing a three-axis piezoelectric load cell is developed to measure local unsteady forces induced on cylinders placed in a cross flow. Verification of the technique is carried out with a two-dimensional circular cylinder. All measurements are made at a Reynolds number of ∼4.8 × 104 and a free-stream turbulence of ∼1.5 percent. The local two-dimensional unsteady lift measurement is found to be in excellent agreement with spanwise-averaged data reported in the literature, thereby validating the feasibility of the present technique. Steady and unsteady force measurements on finite-span circular cylinders are reported and compared with available data in the literature.
Mixing of Fluids in Tanks by Gas Bubble Plumes
Authors: Godon A. M. , Milgram J. H.
Published: October 2009

The need to rapidly mix treating agent into the oil of a ruptured ship tank motivated scale model experiments of mixing in square-bottomed tanks by gas bubble plumes, The mixing time is primarily governed by the gas flow rate, the plume length and the tank base dimensions; and is quite insensitive to tank height. An empirical relationship between the degree of mixing and a single dimensionless variable is developed and an explanation of the relationship in terms of the fundamentals of the flow is provided.
Compressor Erosion and Performance Deterioration
Authors: Tabakoff W.
Published: October 2009

Aircraft engines operating in areas where the atmosphere is polluted by small solid particles are typical examples of jet engines operating under hostile atmospheric environment. The particles may be different kinds of sand, volcanic ashes or others. Under these conditions, the gas and particles experience different degrees of turning as they flow through the engine. This is mainly due to the difference in their inertia. This paper presents the results of an investigation of the solid particle dynamics through a helicopter engine with inlet particle separator. The particle trajectories are computed in the inlet separator which is characterized by considerable hub and tip contouring and radial variation in the swirling vane shape. The nonseparated particle trajectories are determined through the deswirling vanes and the five stage axial flow compressor. The results from this study include the frequency of particle impacts and the erosion distribution on the blade surfaces.
Numerical Calculations of the Breakup of Highly Loaded Slurry Jets
Authors: Situ M. , Schetz J. A.
Published: October 2009

A complete numerical calculation procedure for predicting the effects of mass loading and particle diameter on laminar slurry jet breakup in a low velocity, coaxial gas stream has been developed. The method is based on the Volume of Fluid technique for the Navier-Stokes equations. The severe restrictions involved in earlier treatments have been relaxed. The influence of particle loading on liquid phase density and the influence of particle spacing on drag are included. The particular case considered is a slurry with a methanol liquid phase with aluminum oxide beads in order to compare with some related experimental results. The methanol liquid in the slurry is vaporized due to mass transfer in the gas stream. The variation of the instantaneous jet shape of the methanol slurry jet at low loadings is generally similar to that of an all-liquid methanol jet, but the final shapes at breakup are different. In the region of low mass loading (up to 20 percent), the effects of mass loading are to stabilize the interface and increase the breakup time of the slurry jet with increasing mass loading. Above that region of mass loading (more than 20 percent), the effects of mass loading are to destabilize the interface and decrease the breakup time of the slurry jet with increased mass loading. At the same mass loading condition, a slurry jet with large diameter particles has a more stabilizing effect than one with small diameter particles. Therefore, a slurry jet with higher mass loading and smaller diameter particles breaks up faster.
A Calculation Scheme for Three-Dimensional Viscous Incompressible Flows
Authors: Reggio M. , Camarero R.
Published: October 2009

A numerical procedure to solve three-dimensional incompressible flows in arbitrary shapes is presented. The conservative form of the primitive-variable formulation of the time-dependent Navier-Stokes equations written for a general curvilinear coordiante system is adopted. The numerical scheme is based on an overlapping grid combined with opposed differencing for mass and pressure gradients. The pressure and the velocity components are stored at the same location: the center of the computational cell which is used for both mass and the momentum balance. The resulting scheme is stable and no oscillations in the velocity or pressure fields are detected. The method is applied to test cases of ducting and the results are compared with experimental and numerical data.
Numerical Solution of Stratified Flow Into a Sink: A Criterion for Selective Withdrawal
Authors: Ingber M. S. , Mitra A. K.
Published: October 2009

Steady flow of an inviscid, stratified fluid into a line sink is analyzed numerically using a finite difference scheme. A criterion is proposed to determine the critical Froude number below which selective withdrawal is possible for arbitrary sink position and upstream density profile. For the case of selective withdrawal, a method to determine the withdrawal layer thickness is developed.