bluuebunny/crossref_metadata_2025 huggingface dataset:
The Form Drag of Three-Dimensional Bluff Bodies Immersed in Turbulent Boundary Layers
Authors: Sakamoto H. , Moriya M. , Taniguchi S. , Arie M.
Published: October 2009

Measurements of the pressure distributions on the three-dimensional bluff bodies are correlated with the characteristics of the smooth-wall turbulent boundary layers in which the bodies are immersed. The bluff bodies selected for measurement were a cube and a vertical circular cylinder which can be considered as typical examples of three-dimensional bluff bodies. Experimental data were collected to investigate the effects of (1) the variation of the height of bluff bodies h, (2) the characteristics of the smooth-wall boundary layers in which they are immersed, on the form drag acting on the three-dimensional bluff bodies. For flow with zero-pressure gradient, the form drag coefficients of the cube and the vertical circular cylinder defined by CDτ=D/(1/2ρuτ2h2) are found to be expressed as a power-law function of huτ/ν in the range of h/δ less than about 1.0, where D is the form drag, uτ the shear velocity, ν the kinematic viscosity and δ the thickness of the undisturbed boundary layer at the location of the bluff bodies. For h/δ>1.0, the drag coefficients are independent of the parameter uτ/U0, being uniquely related to h/δ. Further, the pressure distributions along the front centerline of each bluff body can be expressed by a single curve irrespective of both the height of the bluff body and the boundary layer characteristics and show a good agreement with the dynamic pressure in an undisturbed boundary layer at the location of the bluff bodies in the range of about 0.2<y/h<0.7, where y is the distance from the wall.
Transient Response of Fluid Viscoelastic Lines
Authors: Rieutord E.
Published: October 2009

Basic relations and method of solution are given for laminar transient flows in linear viscoelastic circular fluid transmission lines. Using a numerical method to invert the Laplace-Carson transforms, basic step response plots are given for semi-infinite liquid-lines. The method can be immediately applied to any practical problem with linear or explicitly time dependent boundary conditions. Analytical expressions are given for the behavior at the wave front and for large values of time. Also derived are classical parameters characterizing the frequency response.
Drag-Characterization Method for Arbitrarily Rough Surfaces by Means of Rotating Disks
Authors: Granville P. S.
Published: October 2009

An indirect similarity-law characterization method is presented for any arbitrary irregular roughness covering a circular disk. Formulas are presented for converting the measured torques and rotary speeds of this rough rotating disk into appropriate local values at the disk edge required for the characterization.
A Study of Shock Waves in Three-Dimensional Transonic Flow
Authors: Dawes W. N. , Squire L. C.
Published: October 2009

Although a number of inviscid numerical methods have been developed for the calculation of three-dimensional transonic flow in turbomachinery blade passages it is often difficult to compare the results of these calculations directly with experiment. For instance in real machines the overall flow is very complex and it is usually impossible to model the full geometry of the machine, thus it is difficult to trace the sources of the discrepancies which inevitably arise between the measured and calculated results. Even in simpler test cases the experimental results are often strongly affected by viscous effects and flow separations. This paper presents the results of an experimental investigation which generates three-dimensional transonic flow with shock waves using relatively simple geometries and where the influence of viscous effects has been reduced as far as possible. Comparisons with the output of various calculation methods show that even with these simple geometries it is essential to use fully three-dimensional methods to predict the flow development.
Modification of Vortex Shedding in the Synchronization Range
Authors: Zdravkovich M. M.
Published: October 2009

One aspect of the synchronization phenomenon, which has attracted little attention so far, is the timing of vortex shedding in relation to the displacement of a bluff body. Systematic analysis of flow visualization within the synchronization range revealed that the jump in fluctuating forces had a simple fluid mechanics origin. The oscillating cylinder imposed not only its frequency to the wake behind it but also the timing of the vortex shedding. In the lower region of the synchronization range, the vortex formed on one side of the cylinder was shed when the cylinder was near to the maximum amplitude on the opposite side. This timing changed suddenly in the upper synchronization range where the vortex of the same circulation as before was shed when the cylinder reached the maximum amplitude on the same side.
On the Mechanism of Flashing Injection of Initially Subcooled Fuels
Authors: Oza R. D.
Published: October 2009

The mechanisms responsible for flash-boiling injection were investigated. Using an electromagnetic injector developed for this study, propane, methanol and Indolene were heated and injected into a constant-volume vessel. Two regimes of flash-boiling injection were identified. In the first regime, flash-boiling occurs within the injector nozzle without an increase in spray-cone angle. In the second regime, the nozzle exit pressure is sufficiently low that the two-phase compressible mixture created by flash-boiling within the injector nozzle is underexpanded at the nozzle exit and expands externally to increase the spray-cone angle.
Flow Structure and Pressure Loss for Two Phase Flow in Return Bends
Authors: Hoang K. , Davis M. R.
Published: October 2009

Experimental observations of flow structure and pressure loss have been made for froth flow within 180 deg circular pipe bends. Within the bend the distributions of pressure observed reflected the onset of rotation and phase separation effects, whilst secondary flow effects were apparent in the voidage distributions at outlet. Significant components of the overall pressure drop were found both within the bend itself and in the pipe immediately downstream of the bend. Velocity slip between gas and liquid was found to increase observed loss coefficients by approximately 10 percent. The overall loss coefficients were substantially larger than in single phase flow, particularly for bends with larger radius of centerline curvature where they increased by as much as five times the single phase value. The overall pressure loss coefficients were highest for the sharper radius bends, and it was deduced that flow separation and remixing contributed mainly to the increase over single phase loss coefficients.
Experiment on Laminar Flow in a Rotating, Curved Duct of Rectangular Cross Section
Authors: Hoover Mark D. , Sto¨ber Werner , Morawietz Gerd
Published: October 2009

Experimental results are presented here for laminar flow in a rotating, curved duct of rectangular cross section. The duct geometry is that of the spiral duct aerosol centrifuge designed by Sto¨ber and Flachsbart (1969). Primary velocity was measured by laser Doppler anemometry. Secondary flow velocity was characterized by dye injection. The experiment was done in a dynamically similar Plexiglas mock-up of the centrifuge. Water flow in the mock-up simulated air flow in the aerosol centrifuge. The Reynolds number based on hydraulic diameter was 500. The Rossby number was 0.16. The duct aspect ratio was 3.3. Results are compared for flow in a straight stationary duct, the curved duct with no rotation, the curved duct with rotation in the direction of flow and the curved duct with rotation in the direction opposite of flow. There is agreement between the observed flow and the boundary layer theory of Ludwieg (1951).
Radial and Axial Variations in Transient Pressure Waves Transmitted Through Liquid Transmission Lines
Authors: Mitra A. K. , Rouleau W. T.
Published: October 2009

An implicit factorization method has been developed for solving numerically the complete two-dimensional Navier-Stokes and continuity equations for pressure transients in a slightly compressible viscous liquid contained in a rigid pipe. Two problems have been analyzed: (1) The stopping of a steady Poiseuille flow by closure of a valve, and (2), the initiation of a nearly rectangular pressure pulse at the end of the pipe. In problem (1), radial as well as axial pressure variations were found; nearly periodic damped waves exist at the centerline and at the wall, and are approximately 180 deg out of phase. Essentially plane waves are found for problem (2), regardless of whether the fluid is flowing or not, provided that the initial pulse magnitude is not too large; the results show that the viscous effects are concentrated in a thin boundary layer.
Calculated Turbulent-Flow Meter Factors for Nondiametral Paths Used in Ultrasonic Flowmeters
Authors: Lynnworth A. M. , Lynnworth L. C.
Published: October 2009

In applying the ultrasonic contrapropagation method to the measurement of flow in highly attenuating fluids, or to fluids in conduits having only limited access, it is sometimes necessary to interrogate along a path other than the conventional tilted diameter or midradius chordal paths. The meter factor K, which relates the path average to the area-averaged flow velocity, is derived from Nikuradse profiles for several new paths. The results enable one to locate transducers so that for the chosen type of path, K will be (a) minimally dependent on Re, and/or (b) approximately equal to unity, or (c) represented by a simple function of Re. For smooth-wall steady flow conditions, the error in the calculated K’s is estimated as ±2 percent ± the effect due to the disturbance of Nikuradse profiles by the transducers.
Review—Computational Methods for Internal Flows With Emphasis on Turbomachinery
Authors: McNally William D. , Sockol Peter M.
Published: October 2009

A review is given of current computational methods for analyzing flows in turbomachinery and other related internal propulsion components. The methods are divided primarily into two classes, inviscid and viscous. The inviscid methods deal specifically with turbomachinery applications. Viscous methods, on the other hand, due to the state-of-the-art, deal with generalized duct flows as well as flows in turbomachinery passages. Inviscid methods are categorized into the potential, stream function, and Euler approaches. Viscous methods are treated in terms of parabolic, partially parabolic, and elliptic procedures.
Numerical Solution of Laminar Boundary Layer Flow About a Rotating Sphere in an Axial Stream
Authors: El-Shaarawi M. A. I. , El-Refaie M. F. , El-Bedeawi S. A.
Published: October 2009

A finite-difference scheme is developed for solving the boundary layer equations governing the laminar flow about a rotating sphere which is subjected to a uniform stream in the direction of the axis of rotation. Numerical results are presented for the meridional and azimuthal velocities and for the wall-shear-stress components. Also, the angle at which the meridional velocity gradient normal to the wall vanishes is given at values of the parameter Ta/Re2 ranged from zero (the stationary sphere case) to 10000. As compared with the momentum integral technique of Schlichting [8], the present scheme succeeded in obtaining solutions for very considerably larger values of the parameter Ta/Re2.
ASME Measurement Uncertainty
Authors: Abernethy R. B. , Benedict R. P. , Dowdell R. B.
Published: October 2009

The purpose of this paper is to introduce the new ASME measurement uncertainty methodology which is the basis for two new ASME/ANSI standards and the ASME short course of the same name. Some background and history that led to the selection of this methodology are discussed as well as its application in current SAE, ISA, JANNAF, NRC, USAF, NATO, and ISO Standards documents and short courses. This ASME methodology is rapidly becoming the national and international standard.
Correlation and Prediction of Rotating Stall Inception by Divergence Method
Authors: Zika V. J.
Published: October 2009

An empirical correlation of rotating stall inception points of elementary compressors (isolated rotors, stages without prerotation, complete single stages, and multi-stage machines with repeating stages), modeled as equivalent diffusers, is presented. From it, two inception criteria for self-induced rotating stall are derived. Compressor blade rows are classified according to a geometric form parameter, (L/A∞)cor, into two groups, subcritical and supercritical. The subcritical geometries stall at a constant kinematic area ratio AE/A∞, in what appears to be a pure rotating stall mode, which occurs before the airfoil stalls. In supercritical geometries, the rotating stall is delayed until it is triggered by the airfoil stall. Thus, for the latter geometries, the airfoil stall and rotating stall are coincident. In contrast to other diffuser-analog methods, the divergence method determines the stall angle and the stalled flow coefficient rather than the stalled pressure rise.
Performance of Small High Speed Cryogenic Pumps
Authors: Kamijo Kenjiro , Hirata Kunio
Published: October 2009

Several small cryogenic pumps for a liquid rocket engine have been made and tested. These pumps have a small impeller and are characterized by high speed and high head. The main design characteristics of these pumps are as follows: stage specific speeds of from 0.0319 to 0.0766, flow rates from 0.016 to 0.0525 m3/s, pressure rises from 4.9 to 26 MPa, rotational speeds from 16,500 to 80,000 rpm, and impeller diameters from 0.083 to 0.146 m. These pumps, when tested, showed higher efficiency even in the range of small stage specific speeds than any previously reported data on other pumps. This tendency was particularly striking with the two-stage pumps. With regard to pump efficiency measurement, it was made clear that adiabatic efficiency was utilizable for the present cryogenic pumps. The relationship between the adiabatic efficiency and ordinary efficiency was also confirmed by a brief calculation and test results.
Inviscid Shear Flow Analysis of Corner Eddies Ahead of a Channel Flow Contraction
Authors: Meroney R. N.
Published: October 2009

The steady rotational flow of an inviscid fluid in a two-dimensional channel toward a sink or a contraction is treated. The velocity distribution at upstream infinity is approximated by a linear combination of uniform flow, linear shear flow, and a cosine curve. The combinations were adjusted to simulate flows ranging from laminar to turbulent. Vorticity is assumed conserved on streamlines. The resulting linear equations of motion are solved exactly. The solution show the dependence of the corner eddy separation and reattachment on flow geometry and approach flow vorticity and velocity distribution typified by a shape factor.
Turbulent Flow of Incompressible Mixtures
Authors: Roco M. C. , Shook C. A.
Published: October 2009

The spatial nonuniformities and the interactions between the components determine the flow behavior of multicomponent systems. A space/time averaging approach of the governing equations modeling these factors is presented in this paper. It is defined for a weighted averaging volume whose size is related to the local scale of turbulence. Numerical solutions for concentration and velocity distributions are obtained using integral finite volume techniques. The predictions are comapred with good results to multi-species particle slurry flows in pipelines.
Cycle Resolved LDV Measurements in a Motored IC Engine
Authors: Liou T-M. , Santavicca D. A.
Published: October 2009

LDV measurements have been made in an IC engine motored at 1200 rpm. The data rates were sufficiently high to allow the bulk velocity to be characterized in individual cycles. The relative cyclic fluctuation of the bulk velocity was found to be as large as 200 percent. The turbulence intensity was calculated using both the velocity fluctuation with respect to the ensemble average velocity and the velocity fluctuation with respect to the cycle resolved bulk velocity. The former includes both the cyclic fluctuation of the bulk velocity and the turbulence, and therefore gave estimates of the ensemble averaged turbulence intensity which were from 50 to 100 percent greater than that obtained using the in-cycle fluctuation with respect to the bulk velocity. The relative cyclic fluctuation of the time averaged turbulence intensity, calculated over a 64-degree interval in each cycle, was found to be small, i.e., less than 20 percent. The high data rates also made it possible to determine the ensemble averaged temporal autocorrelation function from which the spectral energy distribution and the integral time scale were calculated.
Modeling Criteria for Scaled LNG Sloshing Experiments
Authors: Bass R. L. , Bowles E. B. , Trudell R. W. , Navickas J. , Peck J. C. , Yoshimura N. , Endo S. , Pots B. F. M.
Published: October 2009

This paper presents an overview of the current state-of-the-art in scale modeling of liquefied natural gas sloshing in ship tanks. The numerous potentially significant scaling parameters are discussed in detail and laboratory test data illustrating the effects of the important scaling parameters are presented. In view of current knowledge, an indication of appropriate scaling criteria is presented and recommendations for additional research efforts are outlined.
Experimental Measurements of Hydrodynamic Radial Forces and Stiffness Matrices for a Centrifugal Pump-Impeller
Authors: Chamieh Dimitri S. , Acosta Allan J. , Brennen Christopher E. , Caughey Thomas K.
Published: October 2009

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 constructed 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 displacement 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 skew-symmetric 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.
A Schwarz-Christoffel Method for Generating Two-Dimensional Flow Grids
Authors: Sridhar K. P. , Davis R. T.
Published: October 2009

A new coordinate generation technique, developed by Davis for external flows, is extended to allow for accurate grid generation for a variety of complex internal flow configurations. The approach is based on numerical integration of the Schwarz-Christoffel transformation for polygonal surfaces. It is shown to be second-order accurate with mesh size due to analytic treatment of boundary singularities. The method is flexible enough to allow for treatment of severe internal geometries, for a high degree of control of mesh spacing, and for generation of either orthogonal or nonorthogonal grids. In addition, this technique directly provides the two-dimensional incompressible potential flow solution for internal flows, as well as a simple expression for calculating the grid metric coefficients. Sample cases include symmetric and asymmetric channel, diffuser, and cascade flows.
The Formation of Stratified Combustible Mixtures in Closed Tubes by Molecular and Convective Diffusions
Authors: Badr O.
Published: October 2009

This paper describes a theoretical study on the formation of stratified combustible mixtures in closed long vertical flame tubes. The concentration profiles of the fuel (methane) in air, just before ignition took place, were predicted using a one-dimensional model involving molecular and convective diffusional processes. Phenomenological and experimental justification of the one-dimensional assumption was given and some of the predicted data were compared with experiment for different test conditions. The model appears to have successfully predicted the concentration profiles in some situations where other models failed.
A Flow Visualization Study of a Square Array of Tubes in Water Crossflow
Authors: Weaver D. S. , Abd-Rabbo A.
Published: October 2009

A flow visualization technique has been developed to study the flow behavior in tube arrays in water crossflow. The technique is used to examine flow development in a square array with a pitch ratio of 1.5. Results are presented for turbulence, vortex shedding and fluid-elastic instability including visualization photographs and associated frequency spectra and response curves.
Higher Velocity Resonance of Circular Cylinder in Crossflow
Authors: Shirakashi Masataka , Ishida Yasuhiro , Wakiya Shoichi
Published: October 2009

This report concerns the oscillation of an elastically supported circular cylinder in a uniform crossflow. Several investigators have observed an unexpected subharmonic-like resonance at fv/fn = 3 in addition to the normal one at fv/fn = 1, where fv is the Ka´rma´n vortex shedding frequency and fn is the natural frequency for the cylinder oscillation. Durgin, et al., proposed an explanation of the mechanism for the abnormal resonance at a higher velocity, which he called the Lower Mode Response. In this work comprehensive experiments on the higher velocity resonance were carried out and two alternative mechanisms are proposed for the phenomenon. It is concluded that, as long as the amplitude of the cylinder oscillation is not too large, the description of Durgin, et al., cannot be applied, and that the end effect at the side wall of the measuring channel or the rotation mode oscillation can be attributed to the local maximum amplitude at a higher velocity.
The Effect of Elbow Restraint on Pressure Transients
Authors: Wiggert D. C. , Otwell R. S. , Hatfield F. J.
Published: October 2009

Transient pressure in piped liquid is a function of structural restraint at elbows. If supported rigidly, an elbow causes no appreciable alteration of the pressure transient generated by rapid valve closure. However, if the support is relaxed, significant alteration is observed. Motion of the elbow, driven by axial stresses in the pipe and by the liquid pressure, causes the alteration. Experimental data are presented to support these contentions. Two mechanisms are proposed as causes of the observed interaction of transient pressure and pipe motion. Verification that the mechanisms have been identified correctly is given by comparison of the experimental data to predictions of an analytical model that incorporates the mechanisms.
The Unsteady Potential Flow in an Axially Variable Annulus and Its Effect on the Dynamics of the Oscillating Rigid Center-Body
Authors: Mateescu Dan , Paidoussis Michael P.
Published: October 2009

This paper presents an analytical investigation of the unsteady potential flow in a narrow annular passage formed by a motionless rigid duct and an oscillating rigid center-body, both of axially variable cross section, in order to determine the fluid-dynamic forces exerted on the center-body. Based on this theory, a first-approximation solution as well as a more accurate solution are derived for the unsteady incompressible fluid flow. The stability of the center-body is investigated, in terms of the aerodynamic (or hydrodynamic) coefficients of damping, stiffness and inertia (virtual mass), as determined by this theory. The influence of various system parameters on stability is discussed.
Application of a Reynolds Stress Model to Engine-Like Flow Calculations
Authors: El Tahry Sherif
Published: October 2009

A version of a Reynolds stress turbulence model was adopted and applied for calculating turbulence in internal combustion engine flows. Simultaneously, to improve the numerical accuracy of the computations, a skew-upwind differencing scheme was introduced, thereby replacing the less accurate upwind differencing scheme originally present in the computations. With these modifications applied to an existing code, comparisons were made with measured mean and turbulent velocities of a flow field in an axisymmetric piston-cylinder assembly. The results of the computations were generally encouraging particularly for the mean flow. However, discrepancies were observed which are attributed to either (or both) unknown boundary conditions or shortcomings in the Reynolds stress model.
The Flow Pattern in a Scalene Triangular Duct Having Two Rounded Corners
Authors: Obot N. T. , Adu-Wusu K.
Published: October 2009

Experiments were carried out to determine the pressure drop characteristics and mean velocity distributions in a scalene triangualr duct having two rounded corners. The present data for friction factor are adequately represented by the circular pipe line for laminar flow, but fall below the latter for turbulent flow. The mean flow field is highly asymmetric, the degree of asymmetry being more accentuated along lines parallel to the altitude than parallel to the base.
Experimental Measurement of the Magnus Force on a Rotating Sphere at Low Reynolds Numbers
Authors: Tsuji Yutaka , Morikawa Yoshinobu , Mizuno Osamu
Published: October 2009

The Magnus force on a rotating sphere at low Reynolds numbers was obtained from trajectories of the sphere which impinged on an inclined plate and bounced. An empirical expression for the lift coefficient which is proportional to the angular velocity was deduced by comparing measurements of the range of flight with the solutions of the equation of motion.
A Semipotential Flow Theory for the Dynamics of Cylinder Arrays in Cross Flow
Authors: Paidoussis M. P. , Price S. J. , Mavriplis D.
Published: October 2009

This paper presents a semianalytical model, involving the superposition of the empirically determined cross flow about a cylinder in an array and the analytically determined vibration-induced flow field in still fluid, for the purpose of analyzing the stability of cylinder arrays in cross flow and predicting the threshold of fluidelastic instability. The flow field is divided into two regions: a viscous bubble of separated flow, and an inviscid, sinuous duct-flow region elsewhere. The only empirical input required by the model in its simplest form is the pressure distribution about a cylinder in the array. The results obtained are in reasonably good accord with experimental data, only for low values of the mass-damping parameter (e.g., for liquid flows), where fluidelastic instability is predominantly caused by negative fluid-dynamic damping terms. For high mass-damping parameters (e.g., for gaseous flows), where fluidelastic instability is evidently controlled by fluid-dynamic stiffness terms, the model greatly overestimates the threshold of fluidelastic instability. However, once measured fluid-dynamic stiffness terms are included in the model, agreement with experimental data is much improved, yielding the threshold flow velocities for fluidelastic instability to within a factor of 2 or better.
Second-Order Accurate Explicit Finite-Difference Schemes for Waterhammer Analysis
Authors: Chaudhry M. H. , Hussaini M. Y.
Published: October 2009

Three second-order accurate explicit finite-difference schemes—MacCormack’s method, Lambda scheme and Gabutti scheme—are introduced to solve the quasilinear, hyperbolic partial differential equations describing waterhammer phenomenon in closed conduits. The details of these schemes and the treatment of boundary conditions are presented. The results computed by using these schemes for a simple frictionless piping system are compared with the exact solution. It is shown that for the same accuracy, second-order schemes require fewer computational nodes and less computer time as compared to those required by the first-order characteristic method.
Stable Floating Drops of Liquid
Authors: Dransfield Peter , Davis D. C.
Published: October 2009

There are few reported situations in which a drop of liquid will remain intact in ambient conditions for an indefinite period of time. The paper describes a situation where this happens. The phenomenon was noticed during experiments concerned with the development of a novel rotational speed sensor. It proved to be a substantial rather than a passing occurrence.
Mean Flow Effects on the Low-Wavenumber Pressure Spectrum on a Flexible Surface
Authors: Dowling A. P.
Published: October 2009

The Lighthill theory is extended so that it may be used to determine the flow noise induced by a turbulent boundary layer over a plane homogeneous flexible surface. The influence of the surface properties and the mean flow on the sound generation is brought out explicitly through the use of a Green function. The form of the low-wavenumber wall-pressure spectrum on a rigid surface with an arbitrary mean flow profile is determined. The effect of a coating layer is investigated.
A Mathematical Model for the Analysis of Fluid Flow in a Scroll
Authors: Chen Shou-Rue , Lee Samuel S. , Huang Yuan Mao
Published: October 2009

A three-dimensional mathematical model has been developed to simulate the flow condition in a scroll. Coordinate transformations are used as an effective tool to make the model universal, and the final governing equations are solved by the finite difference method. Three cases of scroll geometry have been investigated and the results are compared with one another to show the effects of scroll geometry on the flow condition at the outlet of the scroll.
A Viscous-Inviscid Interaction Procedure—Part 2: Application to Turbulent Flow Over a Rearward-Facing Step
Authors: Kwon O. K. , Pletcher R. H.
Published: October 2009

The viscous-inviscid interaction numerical procedure described in Part 1 is used to predict steady, two-dimensional turbulent flow over a rearward-facing step. The accuracy of predictions is observed to be quite sensitive to the specification of length scale in the turbulence modeling. The best results are observed when the length scale is specified algebraically downstream of the step using parameters characteristic of the step geometry. Predictions of mean flow quantities and reattachment length are shown to be in generally good agreement with measurements obtained over a range of channel expansion ratios.
Interfacial Instability of an Oscillating Shear Layer
Authors: Shyh C. K. , Munson B. R.
Published: October 2009

The oscillating interface between a very viscous fluid layer (which oscillates as a nearly rigid body with the bounding container) and a relatively inviscid layer becomes unstable under certain conditions. The dimensionless experimental stability results are correlated by a modified form of the classical Kelvin-Helmholtz shear layer instability result.
Turbulent Lubrication Flow in an Annular Channel
Authors: Polderman H. G. , Velraeds G. , Knol W.
Published: October 2009

An analytical and experimental study is presented of the lubrication flow in an annular channel with a moving core. Velocity profiles and wall friction were determined over a Reynolds number range up to 3 × 104 and radius ratios of 0.6 and 0.85. The experimental results are shown to be in good agreement with the predictions of a three-layer gradient-diffusion model.
A Single-Flexible-Cylinder Analysis for the Fluidelastic Instability of an Array of Flexible Cylinders in Cross-Flow
Authors: Price S. J. , Paidoussis M. P.
Published: October 2009

A quasi-static fluidelastic analysis is developed for a single flexible cylinder surrounded by rigid cylinders and subject to cross-flow. Although the analysis is quasi-static, it includes a frequency-dependent term which arises because of flow retardation around the front stagnation region of the cylinder. The combined effect of this flow retardation and of the fluid force field is to produce, for some intercylinder patterns of motion, a negative fluid damping, acting in the sense normal to the flow direction. Using this analysis, the effect of array pattern of the adjacent rigid cylinders is investigated, and it is shown that for some geometries a single flexible cylinder will become unstable while for others it will not. For those array patterns which the theory indicates to be potentially unstable, the variation of critical flow velocity with mass-damping parameter is obtained and compared with available experimental data. In general, the comparison is good, indicating the validity of this analysis.
Limitations of the Boundary-Layer Equations for Predicting Laminar Symmetric Sudden Expansion Flows
Authors: Lewis J. P. , Pletcher R. H.
Published: October 2009

A finite-difference solution scheme is used to study the limitations and capabilities of the boundary-layer equation model for flow through abrupt, symmetric expansions. Solutions of the boundary-layer equations are compared with previous numerical predictions and experimental measurements. Some flow parameters are not well predicted for Reynolds numbers below 200. Global iteration over the flow field to include upstream effects does not significantly influence the predictions. Axisymmetric and two-dimensional flows are investigated. The effect of initial conditions is discussed
Analysis of Subsonic Transitory Stalled Flows in Straight-Walled Diffusers
Authors: Wysocki W. , Kazimierski Z.
Published: October 2009

A simple, semi-empirical procedure is presented for computation of subsonic, turbulent, attached, and transitory-stalled flows in straight-walled diffusers with plenum exit. The procedure employs a zonal model while using the concept of a dividing streamline and integral methods for boundary layer calculations on diverging and parallel side walls. The dividing streamline separates the transitory stall zone, having zero mass flow rate, from the effective flow channel. The procedure predicts the pressure as a function of streamwise location with modest computation times, typically a few minutes on a personal computer and can be useful in design calculations.
A Study of the Internal Forces in a Variable-Displacement Vane-Pump—Part I: A Theoretical Analysis
Authors: Karmel A. M.
Published: October 2009

Growing energy costs continue to motivate the use of variable-displacement pumps in hydraulic systems with varying flow requirements. This study presents an analysis of the internal pressure-distribution in variable-displacement vane-pumps, and of the resulting forces and torques applied to their mechanisms and shafts. This analysis is essential to the study of the pump dynamics and control, the pump design, and the selection of the pump bearings. These forces are shown to be a function of the line pressure, the pump eccentricity, the shaft rotational speed, the fluid bulk modulus, the fluid viscosity, and the design geometry. These forces are composed of two periodic components: a continuous component due to the exposure of chambers to the line port, and an intermittent component due to a hydraulic-lock phenomenon. A design criterion is formulated which eliminates magnitude variations in the continuous component of the radial shaft-load.
Computational Study of Turbulent Gas-Particle Flow in a Venturi
Authors: Chung Myung Kyoon , Sung Hyung Jin , Lee Kye Bock
Published: October 2009

A “two-fluid” model has been applied to predict turbulent dilute gas-particle flow through a Venturi tube. Bulk motion of particles is considered as a secondary fluid flow which exchanges mass and momentum with the primary conveying air stream. Closure of the time-averaged equations is achieved by modelling turbulent second-order correlations with an extended mixing-length theory. Proposed closure model is found to aptly simulate the dependency of the static pressure drop on the particle size, flow rate and the loading ratio.
The Influence of Pressure Gradient on Desinent Cavitation From Isolated Surface Protrusions
Authors: Holl J. William , Billet Michael L. , Tada Masaru , Stinebring David R.
Published: October 2009

An experimental investigation was conducted to study the desinent cavitation characteristics of various sizes of two-dimensional triangular and circular arc protrusions in a turbulent boundary layer for favorable, zero, and unfavorable pressure gradients. The roughness height (h) varied from 0.025 cm (0.01 in.) to 0.762 cm (0.30 in.) and the relative height (h/δ) varied from 0.026 to 2.53. Desinent cavitation numbers (σd) were obtained visually over a velocity range of 9.1 mps (30 fps) to 18.3 mps (60 fps) at an average total air content of 3.8 ppm (mole basis). The data for zero pressure gradient were in fair agreement with data obtained for the same protrusion shapes by Holl (1958). The cavitation number (σd) was correlated with relative height (h/δ), Reynolds number (Uδ/ν) and Clauser’s (1954) equilibrium boundary layer shape factor (G) which includes the effect of pressure gradient. The data show that σd increases with pressure gradient. This result was not expected since it appears to contradict the trends implied by the so-called characteristic velocity theory developed by Holl (1958).
Studies on Performance and Internal Flow of Twisted S-Shaped Bend Diffuser—The So-Called Coiled Bend Diffuser: 1st Report
Authors: Shimizu Yukimaru , Nagafusa Makoto , Sugino Koichi , Nakamura Fusanobu
Published: October 2009

This paper is the result of our research into the twisted S-shaped bend diffuser—the so-called coiled bend diffuser. It is a diffuser with a centerline in the shape of a twisted “S.” Our studies show that the performance characteristics of this bend diffuser are greatly improved when interaction by the bend elements generates an adequate secondary flow inside the diffuser. Full consideration was given to the influence of the divergent angle of the bend elements, consisting of the diffuser or curvature radius ratio of the bend, on these performance characteristics. The relation between diffuser performance and internal flow also was studied. Some guidelines for designing such a high performance diffuser is given.
Vortex Simulation of Propagating Stall in a Linear Cascade of Airfoils
Authors: Speziale C. G. , Sisto F. , Jonnavithula S.
Published: October 2009

A numerical simulation of propagating stall in a linear cascade of airfoils at high Reynolds numbers is conducted using a vortex method which was first developed by Spalart [7] for this problem. In this approach, the vorticity is discretized into a large collection of vortex blobs whose motion is tracked in time by the use of a well-known vortex tracing algorithm based on the Euler equation. The near-wall effects of viscosity are accounted for by the creation of discrete vortex sheets at the boundaries of the airfoils consistent with the no-slip condition. These boundary vortices are then released into the flow field downstream of the separation points which are obtained from a boundary-layer routine. Calculations are presented for a variety of flow geometries. It is demonstrated that (for a given cascade of airfoils, disturbance wavelength, and stagger angle) several different flow regimes are obtained: Attached flow at lower angles of attack and a chaotic deep stall configuration at larger angles of attack with a narrow intermediate range of such angles where propagating stall occurs. The physical characteristics of this propagating stall are parameterized and a quantitative study of the effects of camber and imposed wavelength is conducted. Comparisons are made with previous theoretical and experimental studies.
Laminarization and Reversion to Turbulence of Low Reynolds Number Flow Through a Converging to Constant Area Duct
Authors: Tanaka Hiroaki , Yabuki Hirotaka
Published: October 2009

Airflow in fully developed turbulent state between two parallel plates was accelerated through a linearly converging section, and then it flowed into a parallel-plate channel again. The Reynolds number 2hum/ν was 10,000 and the acceleration parameter K in the accelerating section was 8 × 10−6. Fluctuations of streamwise velocity as well as time-mean velocity profiles were measured at ten traversing stations located along the test channel by a hot-wire anemometer. It was found that the flow, partly laminarized in the accelerating section, continued to laminarize in the first part of the downstream parallel-plate section and then the reversion to turbulence occurred in the way similar to the case of natural transition in a pipe, where the transition proceeds through a regime of the so-called turbulent slug flow.
Acoustically Induced Enhancement of Widening and Fluctuation Intensity in a Two-Dimensional Turbulent Jet
Authors: Thomas F. O. , Goldschmidt V. W.
Published: October 2009

The enhancement of widening rate and turbulence intensity in a turbulent plane jet, due to an acoustic disturbance are considered. Detailed data at a representative Strouhal number suggest a well organized symmetric structural array in the initial region of the flow. These highly organized flow structures act as efficient agents in the transport of energy to the fine-grained turbulence, leading to greater diffusivity, enhanced turbulence and an increase in widening. The data also suggest significant differences in the underlying structure of the natural and excited jet flows, hence putting in jeopardy any generalization of coherent motions especially excited to facilitate their study.
Cavitation Nuclei Measurements With an Optical System
Authors: Billet M. L.
Published: October 2009

Many recent experiments have shown the significance of cavitation nuclei, i.e., gas bubbles and/or particulate; however, progress in making quantitative predictions of cavitation depends upon some knowledge of cavitation nuclei properties such as shape, size distribution and concentration. Thus, research has also been concerned with developing measuring systems that give the statistics of the cavitation nuclei distribution. There are many different systems currently being developed; however, only the accuracy and application of the light-scattering technique initially developed by Keller is addressed in this paper. A model is formulated based on appropriate statistical analysis that defines the accuracy for a given sample size. Very good agreement has been found between microbubble distributions measured with the light-scattering system and with holography. Microbubble distribution data were obtained in the 305 mm water tunnel for different air content levels, tunnel static pressures and several tunnel velocities. These data are compared to nuclei distributions obtained at other facilities.
Cavitation in Large Scale Shear Flows
Authors: Katz J. , O’Hern T. J.
Published: October 2009

Cavitation phenomena were studied in the shear layer behind a two-dimensional sharp-edged plate. Observations were made under stroboscopic light and by flash photography. The first traces of cavitation appear as a series of narrow long axial “strings” suggesting that the major contributor to cavitation inception is the longitudinal (axial) secondary shear layer eddy structure. In a more developed state the cavitation takes the form of a spanwise large eddy structure but the axial “strings” are still evident. The local cavitation inception indices based on the local velocity and pressure scatter between 1.0 and 1.4 when the water is saturated with dissolved air and vary between 0.8 and 1.2 when the air content is reduced to about 30 percent of saturation. These results are in good agreement with a collection of other measurements behind sharp-edged disks that display a consistent increase of the inception index with the Reynolds number.
Optimal Supersonic Ejector Designs
Authors: Dutton J. C. , Carroll B. F.
Published: October 2009

A technique based on a one-dimensional constant area flow model has been developed for solving a large class of supersonic ejector optimization problems. In particular, the method determines the primary nozzle Mach number and ejector area ratio which optimizes either the entrainment ratio, compression ratio, or stagnation pressure ratio given values for the other two variables and the primary and secondary gas properties and stagnation temperatures. Design curves for the common case of diatomic primary and secondary gases of equal molecular weight and stagnation temperature are also presented and discussed.
Critical Condition of Cavitation Occurrence in Various Liquids
Authors: Kamiyama S. , Yamasaki T.
Published: October 2009

An experimental study of cavitation occurrence in benzene, kerosene, gasoline, and Freon 12 was conducted using a square-edged orifice. The experimental results of the desinent cavitation number are compared with the calculated values predicted from two-phase flow analogy. The predicted values show reasonable agreement with experimental data for benzene and gasoline but require some modifications for kerosene and Freon 12.
Stochastic Behavior (Randomness) of Desinent Cavitation
Authors: Oba R. , Ikohagi T. , Ito Y. , Miyakura H. , Sato K.
Published: October 2009

To make clear the stochastic (random) behavior of cavitation desinence, we statistically analyzed the acoustic pressure pulses associated with the cavitation, and defined the desinence by introducing the threshold level selected for the pulse-detection and the control parameters, such as the mean desinent cavitation number, σ¯d, the standard deviation of random variable, σˆd, and those of the time interval between successive pulses. It is shown here that stochastic behavior takes place considerably in desinence, and varies significantly with the random quantities, as well as the air saturation rate of water.
Casing Headloss in Centrifugal Slurry Pumps
Authors: Roco M. C. , Nair P. , Addie G. R.
Published: October 2009

The headlosses in slurry pump casings are caused by the energy dissipation in the flowing liquid-solid mixture, and the particle-casing wall interaction. This paper presents a quasi-three-dimensional flow analysis, in two steps: (1) the casing width-averaged parameters are obtained from the two-dimensional flow simulation in a normal plane to the pump axis, (2) the results are then used for flow computation in the casing radial cross-sections. The governing equations are averaged over the typical time interval for the periodic flow in the casing caused by the finite number of impeller blades. Finite element techniques with linear three-node and quadratic nine-node elements are used in the numerical simulation. The effect of the casing shape on the headlosses is illustrated by comparing the performances of three centrifugal slurry pumps with quasi-spiral, semi-annular and annular casings at various flowrates. The flow recirculated between the casing tongue and impeller shrouds is shown to play a major role in the overall headloss. The flow results may also be used for determining the wear in the casing and thrust on the impeller, as well as for optimizing the casing dimensions.
Automatic Remeshing Scheme for Modeling Hot Forming Process
Authors: Wang H. P. , McLay R. T.
Published: October 2009

Many intrinsic problems associated with the modeling of hot forming processes are described. In the updated Lagrangian finite element technique both the momentum and energy equations are formulated to accommodate moving meshes. Forming processes have several characteristics: no-slip conditions with transient free surfaces; strong thermal and flow coupling; and moving fluid/solid contact points. Due to the no-slip condition at the walls, the Lagrangian mesh is distorted. Two related numerical algorithms, an automatic remeshing scheme and a moving contact point definition, are developed and incorporated into a finite element code for incompressible viscous flow with temperature-sensitive viscosity. The application of this newly developed code for analyzing the glass pressing process demonstrates the capability of this powerful engineering tool.