bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer Aided Design of Mixed Flow Turbines for Turbochargers
Authors: Baines N. C. , Wallace F. J. , Whitfield A.
Published: November 2010

The paper describes a comprehensive computer aided design procedure and its use to investigate mixed flow turbines for automotive turbocharger applications. The outside dimensions of rotor and casing as well as blade angles are determined from one-dimensional design and off design calculations, the detailed blade shape from quasi-three-dimensional analysis and mechanical stressing and vibration programs, and geometric data are presented as outside views and sections of the rotor by a graphics subroutine. The procedure consists of a series of separate programs rather than a single program, so that the designer’s intervention at each stage of the process can be applied. Two mixed flow rotors were designed, manufactured and tested in a specially designed high speed dynamometer. The first was intended to achieve a substantial increase in mass flow over the reference radial rotor without loss of efficiency, while the latter was intended as a direct replacement of the reference radial rotor, but should give more favorable pulse performance when operating in conjunction with an engine due to changes in the operating map viz: a) lower tip speeds for best efficiency, and b) flatter mass flow characteristics. Both effects were predicted by analysis and confirmed by tests.
A Cumulative Fatigue Damage Model for Gas Turbine Engine Disks Subjected to Complex Mission Loading
Authors: Cruse T. A. , Meyer T. G.
Published: November 2010

The objective of a continuing research program is to develop a low cycle fatigue (LCF) damage model which accurately evaluates the life exhaustion of military gas turbine engine disks subjected to complex loading spectra. This paper reports the results of the first phase of the effort and specifically concerns “cold region” disk bolt holes. A simple cycle LCF model is developed which accounts for nonlinear material behavior and the presence of local surface residual stresses due to machining. Nonlinear cumulative damage is clearly observed in specimen and component testing and is successfully modeled by a “double damage” principle in which an initial crack length need not be known explicitly. Testing of full-scale components under complex loading is used to verify the models.
Trace Element Emissions from Coal-Fired Power Plants
Authors: Meserole F. B. , Schwitzgebel K. , Magee R. A. , Mann R. M.
Published: November 2010

The emission rates for 27 major, minor and trace elements from four coal-fired electrical generating stations are presented. The flow rates of each element in each process stream entering and leaving the power plant are given for three of the stations. The exit streams include bottom ash, collected ash and fly ash and vapors in the exhausted flue gases. Elemental material balances were calculated to assess the reliability of the results. The elemental compositions of the particulates in the flue gas were determined as a function of particle size for two stations, one of which was included in the previous material balance study. The two stations studied during this phase used hot-side and cold-side electrostatic precipitators, respectively, to collect fly ash. The concentration effects were evaluated to determine whether the gas temperature during particulate collection affects the distribution characteristics of the elements enriched at the fly ash surfaces.
A Study of the Influence of Reynolds Number on the Performance of Centrifugal Fans
Authors: Phelan J. J. , Russell S. H. , Zeluff W. C.
Published: November 2010

Five types of centrifugal fans were tested at a number of speeds. Included were several geometrically similar fans of different sizes. Dimensionless total pressure and efficiency were plotted against dimensionless flow for each of the Reynolds numbers tested. It was found that for most fan types there exists a threshold Reynolds number. Above this threshold value fan performance is essentially independent of Reynolds number. Below this threshold value fan performance varies with Reynolds number. It is thus shown that a relationship among three dimensionless groups is a more general description of fan performance than the commonly used relationships between two dimensionless groups.
Minimum Spacing of Thermally Induced Cracks in Brittle Solids
Authors: Nemat-Nasser S. , Oranratnachai A.
Published: November 2010

When the temperature at the free surface of a linearly elastic brittle half-plane, which is initially uniform throughout the solid, is suddenly reduced by a large amount and then kept constant thereafter, a thermal boundary layer whose thickness increases with time, forms close to the free surface. Because of the consequent thermal contraction, edge cracks may form within the thermal boundary layer. For a system of equally spaced straight-edge cracks, growing collinearly with increasing thickness of the thermal boundary layer, the average minimum crack spacing is estimated on the basis of: (a) energy consideration, (b) stress consideration, and (c) consideration of stability of the growth of interacting cracks. It is shown that for a given temperature profile, one can develop a general stability chart which, in particular, gives a complete growth regime of the interacting cracks (no crack branching is included).
Design, Fabrication and Field Test Performance of Slug-Type Diamond Compacts Oil Bits
Authors: Daniels W. H. , Thompson D. A.
Published: November 2010

As part of the General Electric Company’s efforts to obtain design and application data for oil and gas well drill bits using the STRATAPAX(T) blank product, a series of slug-type bits were fabricated and tested in both the laboratory and field. This paper describes the design and fabrication techniques employed. Field test data and results are presented and a summary of design modifications and improvements incorporated in the newest bit is included.
Capabilities to Determine Rock Properties at Simulated Geothermal Conditions
Authors: Enniss D. O. , Butters S. W. , McFarland C. B. , Jones A. H.
Published: November 2010

To date, a very limited amount of rock property research has been conducted under conditions simulating actual geothermal resource conditions. Consequently, limitations exist in the definition and modeling of potential goethermal resources. A test machine was, therefore, constructed specifically to meet the geothermal community data requirements in the areas of surface exploration and subsurface evaluation, drilling, reservoir engineering, stimulation, and subsidence prediction. The machine is capable of testing up to 10.2-cm-(4-in-) dia rock cores at confining pressures up to 200 MPa and 538 C (1000 F) temperature. Mechanical and thermal response tests at conditions simulating downhole pressures and temperatures have been conducted thus far.
Geotechnical Issues and Answers During Construction of the Trans-Alaska Pipeline
Authors: Luscher Ulrich , Thomas Howard P.
Published: November 2010

The Trans-Alaska Oil Pipeline completed in 1977 was an unprecedented construction project. Some of the most challenging problems faced were in the geotechnical field. In the format of issues and answers, this paper highlights the activities and decision-making functions of the field engineering organization which was developed. This organization was responsive to the identified need for field confirmation of geotechnical conditions during construction and for assurance of adequacy of as-built construction. Appropriate procedures and lines of communication were established to satisfy these needs.
Impact Motion of a Buoyant Cylinder Released Underwater on a Surface Body
Authors: Chung J. S. , Butler R. G.
Published: November 2010

Surface impact velocities and accelerations of a buoyant module released underwater have been analyzed. The associated equations of motion are presented. The analyses include the effects of cavitation inception possibility, free surface and surface wave action. Velocities and accelerations of rising trajectories are computed as a function of buoyancy, body shape and release depth, with a special application to buoyant modules encasing a deepwater riser. The released module reaches terminal velocity shortly after release. The results and analyses can serve as a practical guide for the operational safety of handling buoyant modules in deep water. The present method of analyses can be applied to other similar bodies.
Semisubmersible Rig Motion Studies Offshore of Alaska and Southern California
Authors: Forristall G. Z. , Kreider J. R. , Reece A. M.
Published: November 2010

Wave and heave measurements were made from the Sedco 706 drilling in the Gulf of Alaska in the winter of 1976-77 and from the Odeco Ocean Prospector drilling offshore of Southern California in the first half of 1977. Wavestaff measurements from the moving semisubmersibles were corrected by adding the heave measured by accelerometers. This wave staff compensation was checked by spectral comparison with data from a Waverider buoy moored off of the Sedco 706 and was found to give excellent results. In addition to increasing the climatological data base for offshore California and Alaska, the measurements were useful for verification of rig motion model tests and computer programs. Prototype data during storm seas has rarely been available for this type of comparison, which is increasingly important since similar methods are being used in the design of tension leg structures. The simultaneous wave profile and heave measurements were analyzed by cross-spectral methods to give the amplitude and phase of the transfer function and the coherence between the signals. The coherences were very high in the energetic part of the spectrum, demonstrating that the heave may be adequately described by a linear transfer function. The measured transfer functions were correctly predicted by the model tests and computer programs.
Finite Cavity Cascades With Low-Drag Pressure Distributions
Authors: Yim B.
Published: November 2010

A method of calculation is presented for the flow characteristics of a two-dimensional supercavitating cascade with finite-length cavities and with an arbitrary pressure distribution. The principle of hydrofoil-airfoil correspondence of the infinite-cavity cascade is utilized. Simplified formulas for the drag and the cavity and foil shapes are derived, and several sample calculations are made. A nonlinear approximation for a thick leading-edge shape is also considered.
Analysis of Unsteady Laminar Boundary Layer Flow by an Integral Method
Authors: Miller R. W. , Han L. S.
Published: November 2010

An approximate integral method of analysis is developed for unsteady laminar boundary layer flows. The case of a flat plate in a free stream with small harmonic velocity oscillations about a steady mean is used to formulate the method. Results are compared with the available experimental data. The essence of the method is to: First obtain asymptotic solutions for limiting cases of the flow under consideration. Then, assume velocity profiles with sufficient generality to include the asymptotic solutions. The profile form functions are determined by applying integral relations (velocity weighted averages of the momentum equation) and compatibility conditions (normal derivatives of the momentum equation evaluated at the boundary). As an example of the method, the second-order mean flow correction is determined for oscillating flow over a flat plate.
Effect of an Oscillating Free Stream on the Unsteady Pressure on a Circular Cylinder
Authors: Hatfield H. M. , Morkovin M. V.
Published: November 2010

An experimental investigation was made of the unsteady pressure on a circular cylinder in a free stream of constant and oscillating velocity. Consideration of possible resonant coupling mechanisms between the Karman vortex street fluctuations and free-stream velocity oscillations showed such coupling to, be insignificant. The frequency of the vortex street fluctuations scales with the mean velocity for high frequency (30 to 50 Hz at mean velocity of 40 fps) oscillation of the free stream.
Status of Fluid Transients in Western Europe and the United Kingdom. Report on Laboratory Visits by Freeman Scholar
Authors: Martin C. S.
Published: November 2010

A report is given of a recent visit to 25 university, governmental, and industrial laboratories, state power boards, and consulting firms in Western Europe and the United Kingdom. A critique of the status and activity of research and development in the area of fluid transients constitutes the report, which also comprises 128 references. Dominant areas of current research effort are apparently cavitation and column separation in pumping mains and condensers of water cooling systems, the effect of the presence of dissolved and entrained gas on pressure surges, and hydraulic resonance in hydraulic machinery and pipelines.
Time-Dependent Pipe Forces Caused by Blowdown and Flow Stoppage
Authors: Moody F. J.
Published: November 2010

Formulations are developed in this study for rapid estimates of time-and-space-dependent pipe reaction forces caused by either sudden blowdown or flow stoppage in a fluid piping system. The analytical model is a uniform pipe with arbitrary bends and friction, a pressure source at one end, and a sudden opening or closing value at the other end. A homogeneous mixture of liquid and ideal gas flows in the system. The method of characteristics is used to obtain fluid-mechanical properties, which then are employed to predict associated pipe loads. A graphical summary of results includes initial and steady blowdown forces, wave propagation forces, and local force-time behavior. The formulations presented are expected to provide a basis for confident, efficient, and economical design of pipe system layout and motion restraints.
An Experimental Investigation of the Transitory Stall Regime in Two-Dimensional Diffusers
Authors: Smith C. R. , Kline S. J.
Published: November 2010

A study of flow behavior of transitory stall in two-dimensional diffusers at low Mach numbers is reported. The changes in flow patterns from stall inception to full-stall are described; the geometries for maximum fluctuations are located. The mean times and distribution of stall build-up and wash-out periods are given for a series of units of varying total angle. The mean times are found to scale on total stall volume, and a nondimensional correlation of stall period is given. The distribution of stall periods, for random inlet fluctuations, is found to be broad and strongly skewed toward lower periods. Comparable results are found in water for R∼104 and in air at R∼105. A further series of tests with periodic inlet disturbances indicates that the stall behavior is modified strongly when the pulsing period is 0.5 to 1.0 times the natuarl mean period, but not otherwise. Details of flow patterns and blockage are summarized.
Similarity Solutions for the Interaction of a Potential Vortex With Free Stream Sink Flow and a Stationary Surface
Authors: Hoffmann J. A.
Published: November 2010

Similarity equations, using an assumed transformation which reduces the partial differential equations to sets of ordinary differential equations, are obtained from the boundary layer and the complete Navier-Stokes equations for the interaction of vortex flows with free stream sink flows and a stationary surface. Solutions to the boundary layer equations for the case of the potential vortex that satisfy the prescribed boundary conditions are shown to be nonexistent using the assumed transformation. Direct numerical integration is used to obtain solutions to the complete Navier-Stokes equations under a potential vortex with equal values of tangential and radial free stream velocities. Solutions are found for Reynolds numbers up to 2.0.
Turbulent Flow in the Entry Region of a Rough Pipe
Authors: Wang Jeng-Song , Tullis J. P.
Published: November 2010

The general characteristics of mean turbulent flow in the entry region of a rough pipe are discussed. A mathematical model is presented for predicting the development of boundary layer thickness, core velocity, and pressure coefficient. Measurements were made of static pressure and velocity profiles in a 12-in. dia pipe at Reynolds numbers between 7 × 105 and 3.7 × 106. Water was used as the fluid. Data are included on the length required for the wall shear stress to become constant, for the boundary layer to reach the pipe centerline and for the velocity profile to become fully developed.
Taylor Vortices With Short Rotating Cylinders
Authors: Cole J. A.
Published: November 2010

Observations of Taylor vortex formation in a short annular clearance show that the final vortex size varies discontinuously with annulus length, ranging from 75 to 115 percent of the theoretical size, and is apparently determined as vortices spread axially inwards from the ends of the annulus by the minimum survival size of the last-formed vortex pair.
Confined Mixing of Multiple Jets
Authors: Fabris G. , Fejer A. A.
Published: November 2010

This study deals with the transfer of kinetic energy from an array of primary jets to a surrounding secondary stream. It explores the basic features of such flows and examines to what extent the results of single jet research may be applied to multiple jet configurations. It presents an analytical technique for estimating the performance of multiple jets and examines in a special multiple-jet test facility the validity of the assumptions used in the analysis. In addition, performance data are presented for a multiple array of 31 primary jets of 1/2 in. ID in a 12 in. ID mixing chamber covering a range of jet velocities up to 186 ft/sec and primary to secondary flow velocity ratios from 2.8:1 to 5:1.
Vortex Formation in the Wake of a Vibrating, Flexible Cable
Authors: Ramberg S. E. , Griffin O. M.
Published: November 2010

The von Karman vortex streets formed in the wakes of vibrating, flexible cables were studied using a hot-wire anemometer. All the experiments took place in the flow regime where the vibration and vortex-shedding frequencies lock together, or synchronize, to control the wake formation. Detailed measurements were made of the vortex formation flow for Reynolds numbers between 230 and 650. As in the case of vibrating cylinders, the formation-region length is dependent on a shedding parameter St* related to the natural Strouhal number and the vibrational conditions. Furthermore, the near wake configuration is found to be dependent on the local amplitude of vibration suggesting that the vibrating cylinder rseults are directly applicable in that region.
An Efficient Method for Simulating Frequency-Dependent Friction in Transient Liquid Flow
Authors: Trikha A. K.
Published: November 2010

An efficient procedure is developed for simulating frequency-dependent friction in transient laminar liquid flow by the method of characteristics. The procedure consists of determining an approximate expression for frequency-dependent friction such that the use of this expression requires much less computer storage or computation time than the use of the exact expression. The derived expression for frequency-dependent friction approximates the exact expression very well in both time and frequency domains. Calculated results for a test system are compared with the experimental results so show that the approximate expression predicts accurately the surge pressures, pressure wave distortion as well as pressure attenuation in a liquid line.
Application of a General Boundary Layer Analysis to Turbulent Boundary Layers Subjected to Strong Favorable Pressure Gradients
Authors: Kreskovsky J. P. , Shamroth S. J. , McDonald H.
Published: November 2010

Theoretical predictions of turbulent boundary layer development under the influence of strong favorable pressure gradients made using a finite-difference calculation procedure are compared to experimental data. Comparisons are presented for low speed flows with and without wall heat transfer as well as for supersonic flows with adiabatic walls. The turbulence model used is governed by an integral form of the turbulence kinetic energy equation and the results are compared with predictions made using a conventional equilibrium turbulence model based upon Prandtl’s mixing length, a Clauser-type eddy viscosity model used by Cebecci and Mosinskis, and a two-equation turbulence energy model of Launder and Jones.
Pulsatile Blood Flow in a Channel of Small Exponential Divergence—I. The Linear Approximation for Low Mean Reynolds Number
Authors: Schneck D. J. , Ostrach Simon
Published: November 2010

The pulsating flow of a viscous, incompressible fluid through rigid circular channels having walls which diverge at a slow exponential rate is examined analytically. Linearized solutions for low mean Reynolds numbers reveal that viscous effects lead to radially dependent phase shifts between different layers of fluid oscillating in the axial direction, and characteristic phase lags between flow and pressure curves. When the Reynolds number and channel divergence are each small, the flow does not separate, but there is a downstream attenuation of both flow and pressure, together with the appearance of a finite radial velocity component. Utilizing data relevant to basal conditions existing in the major blood vessels of the human coronary circulation, it is found (in the absence of any persistent flow anomalies) that the shear stress at the wall is at least one to two orders of magnitude lower than values reported to be damaging to vascular endothelium.
Force and Moment Measurements of Supercavitating Hydrofoils of Finite Span With Comparison to Theory
Authors: Leehey P. , Stellinger T. S.
Published: November 2010

Measurements were made of lift, drag, and moment coefficients, and cavity length for aspect ratio 3 and 5 supercavitating hydrofoils of elliptical planform. These measurements are compared with theoretical predictions obtained from matching asymptotic expansions for large aspect ratio. Good agreement was obtained for lift and drag coefficients for angles of attack from 10 deg to 15 deg and for a wide range of cavity lengths. Theoretical moment coefficients were too large indicating the need for lifting surface corrections.
Measurement of the Propagation of Long-Wavelength Disturbances Through Turbulent Flow in Tubes
Authors: Margolis D. L. , Brown F. T.
Published: November 2010

Phase velocities and attenuation factors for the propagation of small amplitude long wavelength sinusoidal disturbances, measured in a tube with turbulent liquid flow, are reported. Three frequency bands are delineated. A quasi-steady-flow model, based primarily on friction-factor data, is corroborated at low frequencies. An eddy-viscosity model, in which the energy of turbulence fails to respond in quasi-steady fashion to the sinusoidal disturbances, is corroborated at higher frequencies. In a predicted transition band unexpected and dramatic peaks in attenuation and phase velocity were found. A discussion suggests that the phenomenon may be related to deterministic aspects of turbulence production.
The Dynamic Transfer Function for a Cavitating Inducer
Authors: Brennen C. , Acosta A. J.
Published: November 2010

Knowledge of the dynamic performance of pumps is essential for the prediction of transient behavior and instabilities in hydraulic systems; the necessary information is in the form of a transfer function which relates the instantaneous or fluctuating pressure and mass flow rate at inlet to the same quantities in the discharge from the pump. The presence of cavitation within the pump can have a major effect on this transfer function since dynamical changes in the volume of cavitation contribute to the difference in the instantaneous inlet and discharge mass flow rates. The present paper utilizes results from free streamline cascade theory to evaluate the elements in the transfer function for a cavitating inducer and shows that the numerical results are consistent with the characteristics observed in some dynamic tests on rocket engine turbopumps.
An Analysis on the Flow in a Casing Induced by a Rotating Disk Using a Four-Layer Flow Model
Authors: Senoo Y. , Hayami H.
Published: November 2010

An analytical study has been made to clarify the details of the flow between a rotating disk and a stationary casing side-wall with and without an axisymmetric inward through-flow. The flow field between the casing side-wall and the surface of the rotating disk is divided into four layers instead of three in earlier analyses. Proceeding from the casing side-wall to the disk, they are a wall boundary layer, an outward-flow layer, a core and a disk boundary layer. The flow field is determined so that the integrated equations of motion as well as the continuity equation are satisfied for each of the four layers. In the present analysis, least empirical informations relative to a rotating disk are used compared with the theories in the literature. The mechanics of the flow field is explained by the flow model without contradiction, and the predicted radial and axial distributions of velocity and the pressure distribution in the casing agree well with experimental results.
Choking and Mixing of Two Compressible Fluid Streams
Authors: Otis D. R.
Published: November 2010

The mixing of a supersonic with a subsonic stream is treated in a one-dimensional, ideal gas analysis to determine when the mixed flow can be supersonic and to reveal the relationship between certain phenomena described by the terms “forbidden region” of “thermal choking.” A singularity in the equations is shown to divide the mixing process solution curves into two branches: subcritical or supercritical leading, respectively, to subsonic or supersonic mixed states.
Control of Free-Stream Turbulence by Means of Honeycombs: A Balance Between Suppression and Generation
Authors: Loehrke R. I. , Nagib H. M.
Published: November 2010

The effects of honeycomb of different lengths on free-stream turbulence are studied in air with hot-wire anemometry and in water using hydrogen bubbles visualization. The honeycombs are viewed as operators which suppress the level of the incoming turbulence and generate, primarily through documented instabilities, new turbulence with scales characteristic of the shear layers present in their near wake. The suppression of the incoming turbulence appears to be mostly due to the inhibition of lateral components of the fluctuating velocity. The level, structure and decay of the generated turbulence depends, in part, on the instabilities of the shear layers and therefore can be modified by passive devices acting on the flow field immediately downstream of the honeycomb. Thus, fixing a fine mesh screen to the back of the honeycombs leads to substantially different characteristics of the generated turbulence. While in all cases a net suppression of the free-stream turbulence was achieved by the honeycombs, the positioning of the chopper screen in the near wake of the honeycomb led to a much reduced turbulence level far downstream.
Detailed Flow Investigations Within a High-Speed Centrifugal Compressor Impeller
Authors: Eckardt D.
Published: November 2010

Detailed accurate measurements of velocities, directions, and fluctuation intensities were performed with a newly developed laser velocimeter in the internal flow field of a radial discharge impeller, running at tip speeds up to 400 m/s. Relative flow distributions are presented in five measurement areas from inducer inlet to impeller discharge. The impeller flow pattern, which coincides largely with potential-theory calculations in the axial inducer, becomes more and more reversed when the flow separates from the blade suction side, developing a rapidly increasing wake in the radial impeller. The observed secondary flow pattern and effects of channel curvature and system rotation on turbulence structure are discussed with respect to separation onset and jet/wake interaction.
A Finite-Element Method for Through Flow Calculations in Turbomachines
Authors: Hirsch Ch. , Warzee G.
Published: November 2010

A new method for the numerical solution of the meridional through-flow equations in an axial flow machine is presented based on the finite-element method. A rigorous derivation of the pitch-averaged flow equations is presented and the assumption of axisymmetric flow leads, with the introduction of a stream function, to the equation to be solved. A description is given of the finite-element technique which is applied in this problem. The method of solution allows the calculation of transonic stages. Numerical results are compared with experimental data and show very satisfactory agreement. This method appears, therefore, to compare very favorably with the other methods used up to now. Although the present results pertain to axial flow machines, the method is easily applicable to radial flow machines as well and the way of solution for this case is indicated.
Pressure Surge Propagation in Thick-Walled Conduits of Rectangular Cross Section
Authors: Thorley A. R. D. , Guymer C.
Published: November 2010

This paper discusses the propagation of pressure surge phenomena in liquids contained in thick-walled pipes and ducts of rectangular cross section. It is shown that the effects of shear forces and side wall elongation should be considered in calculating the velocity of surge propagation in such conduits. Experimental data from three pipelines are included and compared with the theoretical predictions.
Turbulent Wall Jets With Cylindrical Streamwise Surface Curvature
Authors: Wilson D. J. , Goldstein R. J.
Published: November 2010

The effect of surface curvature on the development of a two-dimensional wall jet is investigated experimentally by direct comparison between a wall jet flowing around the convex surface of a circular cylinder, and its plane flow equivalent. Centrifugal force instabilities introduce rapid mixing of the curved wall jet with its surroundings, and cause significant increases in turbulence intensity and Reynolds shear stress in the jet. Large departures from self-preservation of the turbulence velocity field in the curved jet are observed, while the streamwise mean velocity profiles retain similar shapes for downstream development. Models for curvature effects on eddy viscosity are compared with experimentally measured values, and indicate that a simple correction for the effects of curvature is possible.
Channel Flow Over a Smooth-to-Rough Surface Discontinuity With Zero Pressure Gradient
Authors: Islam O. , Logan E.
Published: November 2010

Measurements are given for the combined effects of a change of surface roughness and a simultaneous change of pressure gradient. The latter is negative in a fully developed turbulent, two-dimensional smooth channel flow upstream of the discontinuity, but is artificially held to a value of zero in the rough channel following the surface discontinuity. Measurements of mean velocity, turbulent intensity, and wall shear stress in the current zero pressure gradient apparatus are compared with similar measurements made in the same apparatus with a negative pressure gradient in the rough channel. Results indicate that removal of the pressure gradient in the rough channel does not affect the growth rate of the internal boundary layer nor that of the sublayer; nor does the modified pressure gradient greatly reduce the transitional overshoot of wall shear stress and turbulence intensity previously observed.
Vertically Downward Two-Phase Slug Flow
Authors: Martin C. Samuel
Published: November 2010

Vertically downward slug flow of air-water mixtures was experimentally investigated in circular pipes of diameter D = 2.60, 10.16, and 14.0 cm. The terminal velocity of descending, stationary, and ascending bubbles in downward flows was measured and correlated with the air and water volumetric flux densities. Except for very small pipe diameters, bubbles in downward flow are unstable and eccentrically located off the pipe axis in regions of lower fluid velocities. Consequently, the value of the flow distribution parameter C0 is less than unity for downward flow, compared to C0 = 1 for rising bubbles in quiescent liquid, and C0 = 1.2 for ascending bubbles in upward flow. Above a certain pipe diameter stable Taylor bubbles are not possible for downward flows. The terminal velocity coefficient C1 is no longer 0.35 for downward flows in relatively large pipes because the unstable bubbles ride the pipe wall, resulting in a higher value of C1.
Flow Control in Wide-Angled Conical Diffusers
Authors: Welsh M. C.
Published: November 2010

Flow control techniques in wide-angled conical diffusers are discussed. Selected performance characteristics of a wide-angled conical diffuser and tailpipe with and without a star flow-control device are also presented. The diffuser performance is sensitive to the star location and geometry and to the diffuser inlet flow conditions. The correct combination of the first two factors for a given inlet condition leads to a significant increase in pressure recovery and flow stability in the diffuser and tailpipe, together with satisfactory mean velocity profiles for entry to downstream duct components.
Experimental Study of Error Sources in Skin-Friction Balance Measurements
Authors: Allen J. M.
Published: November 2010

An experimental study has been performed to determine potential error sources in skin-friction balance measurements. A floating-element balance, large enough to contain the instrumentation needed to systematically investigate these error sources has been constructed and tested in the thick turbulent boundary layer on the sidewall of a large supersonic wind tunnel. Test variables include element-to-case misalignment, gap size, and Reynolds number. The effects of these variables on the friction, lip, and normal forces have been analyzed. Results indicate that some of the intuitive assumptions generally held by designers and users of skin-friction balances may not be valid. For example, it was found that larger gap sizes were preferable to smaller ones; that small element recession below the surrounding test surface produced errors comparable to the same amount of protrusion above the test surface; and that normal forces on the element were, in some cases, large compared to the friction force. The principle contributions of this paper are (1) that users of skin-friction balances can use the data contained in this paper to estimate the errors involved in their measurements, and to make corrections if necessary, and (2) that the results of this study may lead to the development of new and improved devices for direct skin-friction measurement.
An Experimental Investigation of the Control of Surge in Radial Compressors Using Close Coupled Resistances
Authors: Dussourd J. L. , Pfannebecker G. W. , Singhania S. K.
Published: November 2010

The aerodynamic characteristics of centrifugal compressors are examined with special attention given to the range of flows normally in the unstable region. They are examined for the intended purpose of extending the compressor’s useful stable range. Two such means are investigated, but a close coupled aerodynamic resistance designed to achieve negative combined slope showed the greater promise. A number of experiments are performed in which the geometry and location of the close coupled control devices are varied. It is shown that with adequate design, stable operation is possible down to 40 percent of the normal surge flow. This can be done with hardware the configuration of which is practical and with attendant additional losses which are not prohibitive. The rationale and the empirical work are devoted to the single stage case but an examination is made of the stability considerations for the case of multi-stage machines.
Estimation of Centrifugal Compressor Stability With Diffuser Loss-Range System
Authors: Reeves G. B.
Published: November 2010

A method has been developed by which centrifugal compressor flow range and the nature of the pressure ratio characteristic approaching surge can be predicted by use of fundamental impeller exit conditions and diffuser entrance geometry in a system where minimum to maximum flow range is determined by the diffuser. Experimental results from compressor tests demonstrate the influence of these basic variables on flow range. Data from pipe type diffuser configurations designed under the assumptions of the loss-range method verify the capability to estimate flow range. Results of tests confirm the use of the method to predict the shape of the pressure ratio/weight flow characteristic and the location of maximum efficiency at constant speed.
REVIEW—A Critical Review of Turbomachinery Noise
Authors: Cumpsty N. A.
Published: November 2010

The review is written from the point of view of an engineer wanting to understand, reduce, and predict noise from turbomachines. In consequence knowledge gained by theory and, in particular, experiment is emphasized rather than the details of theoretical treatments. Attention is drawn to the surprisingly small interaction between theory and experiment and to the small amount of application that the theories have received. In describing the theoretical models it is the validity or applicability of their assumptions that is emphasized; despite the large number of theoretical treatments published the range of assumptions is quite small. Inevitably the review reflects the emphasis on funding for research by describing mainly high-speed, aeronautical turbomachinery noise. The overall conclusions drawn are rather depressing, with relatively little known even now about noise mechanisms for high speed machinery.
Prediction of Oscillation Frequencies for Unstable Flow Past Cavities
Authors: Rockwell D.
Published: November 2010

The incompressible flow of a shear layer past a cavity can undergo relatively large amplitude organized transverse oscillations which arise from hydrodynamic instability. A model which enables prediction of the oscillation frequencies by accounting for streamwise variations in wave number and amplification factor is put forth. Predicted frequencies compare well with experimental data over a tenfold range of dimensionless cavity length.
Design of Two-Dimensional Wind Tunnel Contractions
Authors: Morel Thomas
Published: November 2010

Design charts for 2-D wind tunnel contractions have been developed using inviscid flow analysis, in which a one-parameter family of wall shapes, based on two cubic arcs, was investigated in detail. The design chart parameters are the maximum wall pressure coefficients at the inlet (as an indicator of the danger of separation at the inlet end) and at the exit (which is related to the exit velocity non-uniformity as well as to separation). For any choice of these two parameters the charts yield the shape parameter and the nozzle length for this particular family of shapes. The charts may be used to design nozzles with no flow separation and with any desired exit velocity uniformity. When the two pressure coefficients are chosen so that separation at both ends is just avoided, the exit boundary layer thickness should be near its minimum. Simple working forms of Stratford’s separation criteria are suggested for the prediction of separation. The results of this study are compared to those obtained earlier for axisymmetric geometries.
A Free-Streamline Model for Bluff Bodies in Confined Flow
Authors: Modi V. J. , El-Sherbiny S. E.
Published: November 2010

A potential flow model is presented for two-dimensional symmetrical bluff bodies under wall confinement. It provides a procedure for predicting surface loading on a bluff body over a range of blockage ratios. Experimental results with normal flat plates and circular cylinders for blockage ratios up to 35.5 percent substantiate the validity of the approach.
REVIEW—Review of Flow Interference Between Two Circular Cylinders in
Various Arrangements
Authors: Zdravkovich M. M.
Published: November 2010

There are infinite numbers of possible arrangements of two parallel cylinders positioned at right angles to the approaching flow direction. Of the infinite arrangements, two distinct groups may be identified: in one group, the cylinders are in a tandem arrangement, one behind the other at any longitudinal spacing; and in the second group, the cylinders face the flow side by side at any transverse spacing. All other combinations of longitudinal and transverse spacings represent staggered arrangements. The tandem arrangement will be treated first. A critical survey of previous research revealed some “odd” features which had been observed and overlooked by various authors. The discontinuity of vortex shedding implies that a similar discontinuity should be expected for the drag force on both cylinders. The measurements of the front (gap) pressures of the downstream cylinder and the base pressures of both cylinders at various spacings reveal a discontinuous “jump” at some critical spacing. The discontinuity is caused by the abrupt change from one stable flow pattern to another at the critical spacing. A new interpretation is given for the existing data on the drag force for both cylinders. The effects of Reynolds number and surface roughness are treated in some detail. Following this, two cylinders arranged side by side to the approaching flow are considered. All the available data on measured forces are compiled together with additional measurements in the range of intermittent changes of drag and lift forces. The bistable nature of the asymmetric flow pattern around each cylinder produces two alternative values of the drag force coupled with two alternative values of the lift force. The introduction of the interference force coefficient exposes the physical origin of two different forces experienced by the cylinders when arranged side by side. Finally, the least reported arrangement of two staggered cylinders is reviewed. The various arrangements are grouped into classes according to the sign of the lift force, or whether the drag force is greater or less than that for a single cylinder. The measurements of drag and lift forces for various arrangements reveal two different regimes for the lift force. In one regime, the lift force directed toward the wake of the upstream cylinder is due to the entrainment of the flow into the fully developed wake of the upstream cylinder. The lift force in this regime reaches a maximum value when the downstream cylinder is near to the upstream wake boundary. In the second regime, at very small spacings, the lift force becomes very large due to an intense gap flow which displaces the wake of the upstream cylinder. The maximum lift force occurs with the downstream cylinder near to the horizontal axis of the upstream cylinder. A discontinuity in the lift force for some staggered arrangements is found and attributed to the bistable nature of the gap flow.
Quasi-Three-Dimensional Laminar Boundary-Layer Separations in
Supersonic Flow
Authors: Vatsa V. N. , Werle M. J.
Published: November 2010

A numerical algorithm is presented for solving laminar, steady, supersonic interacting boundary-layer flows for quasi-three-dimensional configurations. The interaction problem is treated as a boundary-value problem and a salient feature of the scheme is the direct implementation of the downstream boundary condition. Solutions are presented for axisymmetric and swept (yawed) compression ramps for both adiabatic and heat transfer conditions over a Mach number range of 2–6. The results are in good agreement with experimental data and existing theories for axisymmetric cases. For the swept (yawed) configurations, lack of experimental data makes a direct comparison impossible, but the present solutions are found to be in qualitative agreement with earlier studies. In addition, it is shown that the trends obtained for the sweep effects are well predicted by a simple extension of a two-dimensional asymptotic theory.
Interaction Between an Oscillating Bubble and a Free
Surface
Authors: Chahine G. L.
Published: November 2010

Interaction between a collapsing bubble and a free surface is investigated theoretically and experimentally using high speed photography. A limit value for the distance from the free surface to the center of the bubble reported to its radius is found. Under this limit the free surface is not disturbed before the end of the collapse in the first approximation. Only in this case, the method of images can be used and the free surface be replaced by an image-source, symmetrical with respect to the free surface, to the sink representing the bubble. Above this limit, precise measurements of bubble deformation and motion are given. Just after the collapse of the bubble begins, observations show a singular perturbation on the free surface, with the formation of a thin spike directed towards the air. In all cases, buoyancy has no time to take effect, and the bubble is repelled from the free surface while the re-entering jet, formed during collapse, is oriented away from it.
A Method for the Construction of Flow Nozzles and Wind Tunnel
Contraction Sections
Authors: Eichhorn R. , Fox T. S.
Published: November 2010

A method is described for forming a flow nozzle whose cross section varies smoothly from one shape to another. The flow passage consists of fiber glass cloth saturated with epoxy resin cast in place about an elastic water filled rubber diaphragm. An example of such a nozzle, with a circular inlet section and a rectangular exit section was constructed and incorporated in a wind-tunnel design. The flow distribution, excluding the exit boundary layer, is uniform to within 0.5 percent. The exit boundary layer is laminar and steady and the discharge coefficient is 0.989.
Heat Transfer by Laminar Natural Convection Within Rectangular Enclosures
Authors: Newell M. E. , Schmidt F. W.
Published: November 2010

Two-dimensional laminar natural convection in air contained in a long horizontal rectangular enclosure with isothermal walls at different temperatures has been investigated using numerical techniques. The time-dependent governing differential equations were solved using a method based on that of Crank and Nicholson. Steady-state solutions were obtained for height to width ratios of 1, 2.5, 10, and 20, and for values of the Grashof number, GrL′, covering the range 4 × 103 to 1.4 × 105. The bounds on the Grashof number for H/L = 20 is 8 × 103 ≤ GrL′ ≤ 4 × 104. The results were correlated with a three-dimensional power law which, yielded H/L=1Nu¯L′=0.0547(GrL′)0.3972.5≤H/L≤20Nu¯L′=0.155(GrL′)0.315(H/L)−0.265 The results compare favorably with available experimental results.
On the Deposition of Small Particles From Turbulent Streams
Authors: Rouhiainen P. O. , Stachiewicz J. W.
Published: November 2010

It is shown in the paper that the two fundamental assumptions (that of equality of particle and fluid diffusivity and that of purely inertial coasting within the viscous sublayer) on which existing deposition models are based, are untenable under most actual conditions. The concept of Stokes stopping distance, in particular, is shown to be invalid, since the effect of shear-flow-induced transverse lift force, which heretofore has been disregarded, is not negligible when considering the passage of a dense particle through the viscous sublayer. Due to the action of this lift force much lower radial velocities are required at the edge of the sublayer to insure particle deposition on the wall than would be the case if Stokes drag were the only force present. This explains why deposition models based on Stokes stopping distance concept must resort to the use of unrealistically high radial velocities within the sublayer to insure agreement with experimental data.