bluuebunny/crossref_metadata_2025 huggingface dataset:
The Plane Parallel Flow of a Density-Stratified Fluid With and Without a Suspension of Particles
Authors: Healy J. Val.
Published: November 2010

The response of a viscous incompressible nondiffusive fluid containing a dilute suspension of small spherical particles and occupying a semi-infinite region bounded by an infinite plate, when the latter is slowly moved parallel to itself in a prescribed manner normal to the direction of stratification, is studied. In particular, when the system density decays exponentially with distance from the plate, the problem is equivalent to the axial flow of the same system in a long tube. When the particle density vanishes, the problem reduces to the unsteady diffusion of vorticity in a long cylinder, with the “diffusivity” a function of the stratification length, whose solution is well known. A degeneracy occurs in the solution as the density approaches uniformity and this is examined using asymptotic expansions and some exact and asymptotic results for an impulsively moved plate are given. It is found that, for a given stratification, the ratio of the wall stress with particles to that without, increases first and then, after the non-equilibrium overshoot, it continues to increase with time; this is in contrast to the case of uniform density, when the ratio goes asymptotically to a constant value. When the particle density vanishes and the kinematic viscosity of the fluid goes to infinity at very large distances from the plate, the fluid there acquires, in a finite time, a finite velocity that strongly depends on the stratification length.
Behavior of Dilute Polymer Solutions in the Inlet Region of a Pipe
Authors: Bilgen E.
Published: November 2010

The behavior of dilute polymer solutions in the inlet region of a round tube has been analyzed with a Rivlin-Ericksen approximation to describe the fluid properties. It is shown that for dilute polymer solutions, shorter inlet length and increased pressure drop in the inlet region are predicted and that those changes are due to fluid elasticity. Available experimental evidence showed some qualitative support for the inlet-length predicted by the theory. Further, the pressure drops in the inlet region of various tubes have been measured for water and dilute solutions of polyethylene oxide; the results show fair agreement with the predictions.
Dynamic Equivalence of Composite Material and Eigenstrain Problems
Authors: Wheeler P. , Mura T.
Published: November 2010

The variational method is employed for determining the displacement mode shapes and dispersion relations for the problem of plane time-harmonic waves propagating through an infinitely extended, periodically arranged composite material. Numerical results are obtained for the special cases of laminated and fiber-reinforced media. Using variational formulation, the composite problem is compared with the problem of a homogeneous material subjected to eigenstrain and body forces. Necessary conditions are developed for the dynamic equivalency of the two problems. Distributions of eigenstrain are shown which yield the same displacement solutions as the problem of a transverse wave propagating normal to the layers of a laminated media.
On an Accurate Theory for Circular Cylindrical Shells
Authors: Cheng Shun
Published: November 2010

The accuracy of the characteristic roots obtained from solving a pair of complex conjugate fourth-order differential equations which govern the deformation of circular cylindrical shells is studied. Roots of the characteristic equations of the pair of fourth-order equations can be readily obtained in simple closed forms, unlike the Flu¨gge and other unreduced equations for circular cylindrical shells for which roots of the characteristic equations can only be found approximately by complicated numerical processes. In the present paper, roots from the pair of equations are computed for a range of significant parameters and comparisons are made with solutions based on other known equations. These results show that the pair of complex conjugate fourth-order equations has at least the same accuracy as the Flu¨gge equation and is as accurate as an equation can be within the scope of the Kirchhoff assumptions. The pair of complex conjugate governing equations for the homogeneous solutions of circular cylindrical shells is as follows: Lw=0andLw¯=0, in which L=(∇2+1)∇2+i1k∂2∂α2+k(1−ν)∂2∂β2−∂2∂α2∇2+∂2∂β2,L¯=thelinearcomplexconjugateoperatorofL,k=h2a3(1−ν2),h=thickness,a=radiusofcylinder,ν=Poisson’sratio,w=radialdisplacement. The particular solutions can be found from nonhomogeneous equation LLw¯=a4D∇4Z. It may be shown that the simplified equations, such as Donnell, Morley, Novozhilov, and other equations can be readily obtained from the present equation.
A Numerical Study of Separating Supersonic Laminar Boundary Layers
Authors: Werle M. J. , Senechal G. D.
Published: November 2010

A numerical study has been made of the nature of the solution to the supersonic boundary-layer equations when the flow separates from the surface. To this end, implicit finite-difference solutions to the governing equations were obtained for linearly and quadratically retarded flows over flat plates for a Mach number range of 2–15. Both extremely hot and cold-wall conditions are considered. The resutls of this study give strong evidence that all noninteracting flows are singular at separation.
The Response of an Elastic Solid to Nonuniformly Moving Surface Loads
Authors: Freund L. B.
Published: November 2010

Wave motion in an elastic half space subjected to nonuniformly moving surface loads is studied. The sudden application and subsequent motion of either a line load or a pressure step is considered. In each case the load is applied normal to the surface, the shear traction being zero, and the subsequent motion is such that the solid is in a state of plane strain. The motion of the load or step is allowed to be quite general, including acceleration or deceleration through the various characteristic speeds of the material. Both problems are formulated, and the line load problem is solved in detail. Properties of the solution are discussed, with emphasis on the determination of the wave fronts for any particular load motion. It is also shown that singularities in surface displacement are generated as the load accelerates or decelerates through the Rayleigh wave speed. On the other hand, if the load moves at the Rayleigh wave speed for any finite time, such singularities also appear. Finally, the application of the analytical technique to nonuniformly moving dislocation problems is discussed.
Lure Behavior in Trolling
Authors: Soechting J. F. , Paslay P. R. , Paslay P. W.
Published: November 2010

Simplified governing equations for line length, velocity, and lure hydrodynamic characteristics are used to determine the depth at which a lure runs in typical noncommercial fishing. The hydrodynamic characteristics of five typical lures were determined experimentally and their line length-velocity-depth relations, as predicted by the governing equations, are reported graphically.
Hypersonic Rarefied Viscous Interaction Over a Semi-Infinite Flat Plate
Authors: Kasza K. E. , Chow W. L.
Published: November 2010

The problem of hypersonic rarefied viscous interaction over a semi-infinite flat plate has been solved using Meksyn’s asymptotic method of integrating the full nonsimilar boundary-layer equations. The primary phenomena of “incomplete compression”, velocity slip, and temperature jump are incorporated into the analysis. Results are obtained for induced wall pressure, skin friction, and Stanton number variation along the plate. Detailed results are also obtained for developing velocity profiles and shock location. The pressure plateau within the merged layer region is correctly predicted and the solutions merge far downstream with the strong interaction solutions where rarefied gas effects become negligible.
A Numerical Study of Plane Longitudinal Waves in a Nonlinear Viscoelastic Material
Authors: Blake T. R. , Wilson J. F.
Published: November 2010

A numerical study of plane longitudinal waves in a nonlinear viscoelastic material is presented. The constitutive relationship and the conservation equations, in Lagrangian form, are formulated in an explicit first-order finite-difference manner. The mechanical behavior of the material is described by means of state and orientation variables and the associated differential equations. With the use of the numerical procedure we model wave-propagation experiments in polymethyl methacrylate and derive a constitutive relationship for that material. We then use this constitutive equation in a numerical study of the evolution of steady-state waves and we show that the time for the formation of these waves is inversely proportional to magnitude of the imposed velocity.
Static Determinacy in the Theory of Finite Width Foil Bearings
Authors: Langlois W. E.
Published: November 2010

The assumption of “perfect flexibility” is shown to be self-consistent in an important class of finite-width foil bearing problems. When the membrane equations are written in the “stretched coordinates” of foil bearing theory, the usual edge conditions on the tape result in a statically determinate problem. The tape dynamics couples to the Reynolds lubrication equation through a single force-balance equation which does not entail the elastic strain.
Experimental Determination of the Transient Uniaxial Stress in a Bar by Dynamic Photoplasticity
Authors: Chase K. W. , Goldsmith W.
Published: November 2010

The transient compressive stress in a slender bar composed of a rate-dependent photoplastic material, subjected to uniaxial impact, has been determined by dynamic photoplasticity and compared to a finite-difference solution of the uniaxial wave equation. A mechanical constitutive equation based upon tests on this substance, a styrene-polyester copolymer, over eight decades of strain rate was employed in this analysis. The experimental arrangement provided for the impact of a pneumatically driven aluminum rod on a pressure bar which had an 8-in. bar of the copolymer in contact at its distal end. The stress pattern, reaching amplitudes of 7000 lb/in.2, was observed by means of filtered polarized light emanating from a Xenon flash tube and was recorded by a high-speed framing camera. The experimental results and the predicted numerical values showed close correlation when the impact velocities were properly matched. Comparisons could be effected only during the loading process since constitutive relations for the material were not obtained for unloading. The dynamic photoplastic data exhibited an oscillation behind the wave front which was attributed to lateral inertia effects.
Fluid Dynamics of the Circular Porous Slider
Authors: Wang Chang-Yi
Published: November 2010

A fluid of constant density is forced through the porous bottom of a circular slider which is moving laterally on a flat plane. We assume the radius of the slider is much larger than the gap width between the slider and the plane. The Navier-Stokes equations reduce to a set of nonlinear ordinary differential equations. These equations are solved by three methods: series expansion for small crossflow Reynolds number R, matched asymptotic expansions for large R, and also exact numerical integration. The approximate solutions are compared with the numerical results, which is also an exact solution of the Navier-Stokes. Lift and drag are calculated. If everything else is held fixed, both lift and drag increase rapidly although at different rates, with decreasing gap width.
The Shrink-Fit of a Cylindrical Shell Onto a Discontinuous Rigid Mandrel
Authors: Bogy D. B.
Published: November 2010

This axisymmetric contact problem is solved using Kirchhoff-Love thin shell theory for a mandrel with a gap and for a plug, either of arbitrary length. The limiting case of a very long gap is of particular significance and is also solved. Representative numerical results are presented in graphical form and sufficient numerical results are presented in tabular form to permit easy computation of any desired aspect of the solution.
The Impact of an Elastic Sphere on a Thin Elastic Plate Supported by a Winkler Foundation
Authors: Fisher H. D.
Published: November 2010

This paper investigates the elastic impact of a sphere on a thin plate which is in continuous contact with a foundation. The reaction pressure is considered to be proportional to the local deflection (Winkler hypothesis). A solution technique, which was originally developed to analyze the impact of a rigid sphere on a viscoelastic plate, is modified for application in the present study. The contact force, the coefficient of restitution, and the contact time are computed for a wide variation in the two dimensionless parameters which are required to describe a given problem. For the limiting cases of impact on a half space and impact on a thin plate supported by a rigid foundation, the contact time computed here is shown to correlate with the calculations of earlier investigators.
Shock-Wave Attenuation by Resilient Scatterers
Authors: Geers T. L.
Published: November 2010

The scattering of plane, transient acoustic waves by soft bodies is examined from the standpoint of shock-wave attenuation in fluids and solids. Asymptotic results in powers of scatterer stiffness are obtained that establish a stiffness range for which substantial and thorough attenuation is possible. This stiffness range lies between two extremes: one in which the scatterer acts as a rigid inclusion offering no pressure reduction benefits, and the other in which the scatterer suffers ultimate collapse in the manner of a cavity, with the concomitant generation of a large rebound pulse.
High Frequency Response of Beams
Authors: Parker R. P. , Neubert V. H.
Published: November 2010

In developing the relationship of the normal mode solution for a vibrating rod to the pyrotechnic shock problem, a detailed analysis is presented using the Timoshenko theory to obtain the transient lateral response of a cylindrical rod with free ends to a short duration half sine pulse of either moment or shear applied to one end. Two different series solutions are used and the rates of convergence are compared near the boundary. Results are compared with experimental data.
Observations of Wave Motion and Upstream Influence in a Stratified Fluid
Authors: Hurdis D. A. , Pao H.-P.
Published: November 2010

The disturbances created by the motion of a vertical flat plate within the density-gradient region between two superimposed liquid layers were examined both experimentally and numerically. An upstream influence, which resulted from a balance of inertial and gravitational forces, was observed, and it was possible to predict the behavior of this influence with the numerical model. The prediction included a description of the propagation of the upstream influence to steadily increasing distances from the flat plate and the shapes and magnitudes of the velocity profiles.
An Experimental and Theoretical Study of Transitional Turbulent Pulsatile Flow in a Channel
Authors: Thomas L. C. , Min J.
Published: November 2010

Experimental measurements of the time scale τ(t) of the burst phenomenon are reported for laminar-transitional turbulent, fully developed, pulsatile flow in a channel. Theoretical predictions for τ(t) which are developed on the basis of a quasi-steady surface renewal formulation are shown to be in good agreement with the data.
Propagation of a Shock Wave Front Across a Curved Fluid-Solid Interface
Authors: Bennett B. E. , Herrmann G.
Published: November 2010

Geometric optics, or the ray theory, is used to investigate the effect of pulse reflection and transmission at a curved fluid-solid interface. In particular, the problem of a plane pressure pulse, supported by an acoustic fluid, impinging on a plane symmetrical elastic body whose cross section is delineated by circular arcs is considered. The response of the solid is determined along its center line to reflection at the back interface with another fluid. Consideration of the special case in which the fluid densities are zero indicates that special care must be exercised in dealing with the in vacuo problem, and particularly in specifying the boundary conditions in that instance.
On the Momentum Correction Factor in Pulsatile Blood Flow
Authors: Buthaud H.
Published: November 2010

The time-varying expression of the momentum correction factor for the study of wave propagation in pulsatile blood flow is modified to take into account the temporary sign reversal of the velocity. A constant value for this factor is also proposed as a possible alternative to usually adopted values.
On the Structural Behavior of Progressively Mined Solution Cavities in Salt
Authors: Fossum A. F.
Published: November 2010

The stress field and the time dependent deformation around a solution cavity in rock salt are shown to be sensitive to the details of the excavation process and to the prevailing tectonic stress field. An analysis procedure is developed whereby an incremental excavation procedure and a creep routine are incorporated simultaneously into an axisymmetric finite element code.
Traveling Loads on Viscoelastic Plates on Nonlinear Foundations
Authors: Padovan J.
Published: November 2010

Within the framework of Kirchhoff-type prestressed plate theory, the steady-state response of a viscoelastic plate strip on a nonlinear dissipative foundation to the action of general traveling loads is considered. Since an hereditary integral-type viscoelastic constitutive model is employed, the governing field equation is of the nonlinear integropartial-differential type. To solve the stated problem, a modified perturbation procedure is employed. To remove the occurrence of secular terms, since the governing field equation is nonholonomic, a local potential operator is used to develop a hierarchy of integral constraints. Based on this approach, arbitrary traveling loads, hereditary-type viscoelastic modeling and foundation nonlinearity can be handled. Employing the solution, the results of several numerical experiments are presented. These emphasize the effects of dissipation, foundation nonlinearity as well as the action of periodic traveling loads.
Saint-Venant’s Principle for a Helical Spring
Authors: Batra R. C.
Published: November 2010

We consider a linear elastic helical spring of arbitrary length and of uniform cross section loaded by a self-equilibrated force system at one end only. We show that the elastic energy, stored in the portion of the spring beyond a certain distance from the loaded end, decreases exponentially with the distance. We thus establish an analog of Toupin’s version of the Saint-Venant principle for a helical spring.
A Comparison of Deformation and Flow Theories Under Dynamic Loading Conditions
Authors: Upadhyay P. C. , Stokes V. K.
Published: November 2010

Numerical solutions have been obtained for the problem of the dynamic expansion of a circular hole in an infinite plate, due to the imposition of a constant acceleration at the hole boundary, for a deformation theory model based on the Ramberg-Osgood stress-strain relation. In order to assess the validity of using deformation theories for problems in which dynamic plastic deformations may occur under nonproportional loading conditions, these solutions have been compared with those for the equivalent flow theory model.
Consolidation in Compressible Mixtures
Authors: Kenyon D. E.
Published: November 2010

Comparisons between linear theories of incompressible and compressible porous media reveal two phenomena unique to phase compressibility: (1) boundary layers of fluid pressure and filtration will appear at noncontact loading surfaces in a compressible mixture, and (2) a small measure of mixture compressibility does not always imply that the transient behavior of a compressible mixture is only a small departure from that of an incompressible mixture. The relationships between the compressibility parameters of the present theory and those of Biot are given.
Stress in Glass Fibers Induced by the Draw Force
Authors: Rongved L.
Published: November 2010

This paper analyzes the viscoelastic phase of the forming process of glass fibers when the viscous and elastic material constants are variable with a coordinate normal to the fiber axis. This condition may be due to either a temperature gradient or a material inhomogeniety as in clad fibers. One employs the equations of classical viscoelasticity and obtains an approximate solution for the fiber stress. The analysis bears out the findings of previous investigators that the force used to draw such fibers from hot preforms or melts produces a viscoelastic stress that has large gradients directed transverse to the fiber axis. As the fiber cools, a strain proportional to the draw force is frozen into the fiber which contributes to the residual fiber stress. The merits of a solution for the frozen stress used by previous investigators is discussed. It is shown that an increase in the draw force can either weaken or strengthen a fiber depending on the attendant physical conditions, and one discusses how this factor may be exploited. The force induced stress is determined theoretically for two specific fibers. An experimental determination of the force-induced stress is given which is in substantial agreement with the theory.
A Quadrature Representation of the Viscoelastic Analogy in the Frequency Domain
Authors: Dasgupta G. , Sackman J. L.
Published: November 2010

An analytical continuation form of the viscoelastic correspondence principle is presented accounting for frequency dependent complex Lame´ constants. This formulation is especially useful when the elastic frequency response function is available only in numerical form.
The Dynamic Hole Expansion Problem for a Plate of Elastic-Perfectly Plastic Material
Authors: Upadhyay P. C. , Stokes V. K.
Published: November 2010

Numerical solutions have been obtained for the problem of the dynamic expansion of a circular hole in an infinite plate of elastic-perfectly plastic material, due to the imposition of a constant acceleration at the hole boundary, for three different materials. It has been shown that Freiberger’s assumption, concerning the vanishing of the tangential component of stress in the plastic region, is not valid.
A Method for the Solution of the Unsteady Boundary-Layer Equations
Authors: de Socio L. M. , Pozzi A.
Published: November 2010

The equations of the unsteady, incompressible laminar boundary layer are considered in the case of two-dimensional flow and in the presence of a pressure gradient. The fundamental equations are cast into a more manageable form through the expansion of the unknown velocity by Taylor’s formula, in terms of a suitable variable. Consideration is also given to the truncation error. Several examples were carried out to show that even the first term in Taylor’s formula provides good accuracy in many circumstances.
Natural Modes and Natural Frequencies of Uniform, Circular, Free-Edge Plates
Authors: Itao K. , Crandall S. H.
Published: November 2010

The natural modes and natural frequencies for the first 701 modes of vibration of a uniform thin circular plate with free edges are tabulated for a homogeneous isotropic material with Poisson’s ratio ν = 0.330.
Critical Force in the Buckling of Drill Bits
Authors: Bobisud L. E. , Christenson C. O.
Published: November 2010

We consider a fourth-order nonlinear system of differential equations that describe the slope of a steadily rotating flexible rod, one end of which is clamped, and the other end of which is “hinged.” There is a force directed along the length of the rod. We graph against speed of rotation the maximum force that can be applied before buckling occurs, using linearized equations.
In-Plane Vibrations of Thick Circular Rings With T or I Cross Sections
Authors: Lecoanet H. , Piranda J.
Published: November 2010

This paper deals with the problem of eigenfrequencies and eigenvectors for rings whose cross section may be decomposed in basic rectangular cross sections. The solution is derived from a solution of the in-plane eigenvalue problem for rectangular cross-section thick rings. A good agreement between theoretical results and experimental data is obtained.
Flow in a Whirling Rotor Bearing
Authors: Brindley J. , Elliott L. , McKay J. T.
Published: November 2010

We examine the flow in the annular region between two infinitely long parallel circular cylinders when the axis of the inner cylinder travels in a circular whirl orbit about the axis of the outer cylinder. One or both of the cylinders rotate with constant angular velocity. The analysis is restricted to small values of both clearance ratio and modified Reynolds number. Corrections for curvature and inertia effects are included using an expansion in terms of the above parameters. The resultant forces exerted by the fluid on the cylinders are calculated for the cases when the bearing clearance is completely filled with lubricant and also when cavitation occurs.
On the Barber Boundary Conditions for Thermoelastic Contact
Authors: Comninou Maria , Dundurs J.
Published: November 2010

A dilemma arising from the conventional boundary conditions for thermoelastic contact was observed by Barber in treating the indentation of an elastic half space by a rigid sphere. If the sphere is colder than the half space, the interface tractions are necessarily tensile near the periphery of the contact region. In order to overcome this difficulty, Barber introduced the idea of an imperfect contact zone. An asymptotic analysis of the transitions between the different zones is carried out in this article. It is found that, if heat flows into the body with the larger distortivity, a direct transition from perfect contact (no resistance to heat flow) to separation (no heat flow) is possible, the zone of imperfect contact (vanishing contact pressure and some resistance to heat flow) is automatically excluded, and the heat flux is square-root singular at the transition. If heat flows in the opposite direction, no direct transition from perfect contact to separation is possible, there must be an intervening zone of imperfect contact, and the heat flux is logarithmically singular at the transition from perfect to imperfect contact. The transition from imperfect contact to separation is always possible, and it is smooth. These conclusions are direct consequences of the inequalities that must be enforced because of the unilateral nature of thermoelastic contact.
Waves From Suddenly Punched Hole in Plate Subjected to Uniaxial Tension Field
Authors: Haddow J. B. , Mioduchowski A.
Published: November 2010

The plane-stress unloading waves emanating from a suddenly punched circular hole in a thin plate subjected to a uniform uniaxial tension field are considered. It is assumed that the plate is linearly elastic and that the plugging of the hole takes place over a finite time with the stress components at the circumference of the hole decreasing, linearly with time, to zero. A modification of the method of near characteristics, introduced by Sauer [1], for problems of gas dynamics with two or three spatial variables is used to obtain a numerical solution to the governing equations, which have three independent variables, time and two plane polar coordinates. The numerical results obtained approach those for the well-known statical solution, for a hole in a plate subjected to a tension field [2], as the time after the arrival of the wave front becomes large.
Lateral Motion of an Axially Moving String on a Cylindrical Guide Surface
Authors: Ono K.
Published: November 2010

Lateral motion of an axially moving string on a cylindrical guide surface is investigated theoretically and experimentally. By deriving and solving the basic equation of the system, it is found that the axially moving string slips laterally on the fixed guide surface similarly to one-dimensional heat flow. The transfer characteristics of the string lateral displacement from one side to the other over the guide surface depends on the string transport direction, if the circumferential and axial friction coefficients between string and guide are different from each other. The solution for a rotary guide can be obtained as the limiting case where the circumferential friction coefficient is zero and the axial friction coefficient is infinity.
Controlling the Tonal Characteristics of the Aerodynamic Noise Generated by Fan Rotors
Authors: Mellin R. C. , Sovran G.
Published: November 2010

A technique has been developed for selecting circumferentially-unequal blade spacings that will reduce the tonal annoyance of the aerodynamic noise generated by the rotors of fans. The procedure has been successfully applied to a number of axial-flow fans. The predictions of harmonic spectra are based on an experimentally-determined sound-pressure wave shape for the individual blades of such fans. However, the technique can be extended to other types of tonal-annoyance problems provided that the particular relevant sound-pressure wave shape is determined. Unequal blade spacings that will produce a particular degree of “whiteness” in the noise with a minimum departure from equal spacing are tabulated for a range of blade numbers. Both unbalanced and naturally balanced blading arrangements are considered. A survey technique is also outlined for those applications in which it is important to reduce a particular frequency, or where blending with a given background noise must be achieved.
Time Optimal Control for a Class of Common Random Disturbances
Authors: Oldenburger R. , Smith N. P.
Published: November 2010

This paper concerns the time optimal control of a system variable where the controlling input is bounded, as is usually the case, and the system is subject to arbitrary disturbances. An arbitrary disturbance is made up of uncontrollable portions followed by controllable sections. In industrial practice controllers are sized, as for example as to power, to fit the system so that the disturbances encountered are primarily made up of uncontrollable sections followed by controllable portions of sufficient duration for the controller to bring the system to equilibrium. The control designer wishes to have optimal control for any disturbance made up of such an uncontrollable portion followed by a sufficiently long controllable section. Here this problem is solved with the aid of the maximum principle for the class of second order systems which describe almost all governor-engine applications to first approximation accuracy. Previous attempts to solve this problem involved assuming statistical properties of the disturbance thus severely restricting the class of applications. Here only those statistical properties required to implement optimal control are determined. A single control function is derived which suffices to yield optimal trajectories.
Evaluation of a High Hub/Tip Ratio Centrifugal Compressor
Authors: Groh F. G. , Wood G. M. , Kulp R. S. , Kenny D. P.
Published: November 2010

A centrifugal compressor stage with an unusually high inlet hub/tip ratio of 0.87 was designed for a pressure ratio of 2.0 at a corrected mass flow of 2.45 lb per sec. The geometry was selected so that the centrifugal stage could replace several of the last stages of a multistage axial compressor. The stage was tested with two diffuser schemes. One diffuser consisted of a series of drilled conical pipes, whereas the other employed multirow vaned cascades. Sea level aerodynamic tests of the compressor stage with each diffuser showed a peak total-to-total efficiency at design speed of 83.8 percent for the pipe diffuser and 82.9 percent for the vaned cascade diffuser. Additional tests were conducted with a vaneless diffuser to determine effects of impeller discharge tip clearance and inlet prewhirl on impeller performance.
An Analytical and Experimental Study of a Vortex Pump
Authors: Schivley G. P. , Dussourd J. L.
Published: November 2010

A pump which operates by setting up a vortex in a chamber in front of the impeller is often called a vortex pump. Vortex pumps by virtue of this design have a large free and open flow passage which permits the pumping of solid materials without danger of obstruction. They are thus in common use as materials handling pumps. A one-dimensional analytical model of such a pump is created, handling a Newtonian single-phase fluid. Calculated performance parameters are compared with those measured on a laboratory model. Overall pump characteristics are also computed and compared to those of a number of test pumps of various geometries. Finally, an examination is made of the similitude parameters governing this style of pump.
Measurement of Steam Quality in Two-Phase Upflow With Venturimeters and Orifice Plates
Authors: Collins D. B. , Gacesa M.
Published: November 2010

An experimental program has been carried out to investigate the measurement of steam quality with Herschel venturimeters and orifice plates. Data are presented for vertical upflow of steam/water mixtures at 980 psia, through venturimeters and orifice plates of 2 1/2-in. and 3-in. pipe size and with four throat-to-pipe diameter ratios. Total flow rates ranged between 15,000 and 100,000 lb/hr and steam qualities between 5 and 90 percent. The data have been correlated in a manner enabling explicit calculation of steam quality, from measurements of other experimental parameters. Comparison with other data shows that the orifice plate correlation may be used to calculate steam qualities in the range of operating pressures 70–980 psia and in pipe sizes from 2 1/2 to 8 in.
A Two-Dimensional Analysis of a Heated Free Jet at Low Reynolds Numbers
Authors: Krishnan S. , Glicksman L. R.
Published: November 2010

To spin polymers and glass into continuous fibers, hot molten material is made to flow through a nozzle into air, thus forming a free liquid jet. This cools as it proceeds through the air and the solid fiber is collected on a rotating drum. This maintains a tension on the jet causing it to attenuate as it cools. An approximate integral technique is presented to investigate the relative importance of two-dimensional fluid mechanics for a variable viscosity glass jet in the region of the jet within four to five nozzle diameters of the nozzle exit. The results, when compared with those of an existing analysis based on one-dimensional velocity and temperature profiles, indicate that two-dimensional fluid dynamic effects exert very little influence on the jet shape while small changes in the temperature distribution cause significant changes in the jet behavior. A limited number of experiments performed with a chlorinated polymer provided a very simple and inexpensive means of modeling glass flow and also served to verify the results of the existing analysis over a different range of property values as compared to glass.
On the Correlation of Analytical and Experimental Free Shear Layer Similarity Profiles by Spread Rate Parameters
Authors: Korst H. H. , Chow W. L.
Published: November 2010

Analysis of turbulent isobaric free jet mixing normally requires the introduction of suitably formulated viscosity models. Similarity solutions can then be established which contain one empirical parameter. Such a parameter, however, not only describes the rate of spread of the mixing region, but also determines in detail the structure of the entire flow field. It is pointed out that this “spread rate parameter” σ depends on the selected viscosity model, the method of theoretical analysis, and the definition of profile matching. A comparison of different theoretical profiles can only be accomplished after these factors are properly recognized. Any attempts to contribute to the rather incomplete knowledge of the spread parameter must be cognizant of its dependence on the theoretical mixing model employed. This paper also establishes theoretical relations which allow comparison and consolidation of information based on different analytical concepts.
On the Influence of Water Turbine Characteristic on Stability and Response
Authors: Goldwag E.
Published: November 2010

Given a real turbine characteristic, equations giving discharge and torque are derived in terms of certain characteristic slopes, speed changes, and pressure deviations. It is shown that for the majority of reaction turbines the flow through the machines is speed dependent and the effect of this phenomenon on the pressure dependence of flow is examined and found to be significant. Similarly the conventional representation of the pressure dependence of torque is shown to be correct only in the case of one particular type of turbine. A formula allowing the establishment of the correct relationship for any characteristic is given. The nonlinearities of the quantity-gate and torque-gate relationships are examined, and the concept of effective gate is introduced in order to improve the accuracy of any predictions. The modified relationships are used in establishing the bounds of the region in which stable operation of the unit can be achieved, and these are shown to vary both from turbine type to type and with gate on any particular turbine, depending on the slope of the appropriate unit quantity-unit speed curve. Similarly, the governor parameters leading to critical damping are shown to be a function of this characteristic slope. The analysis leads to the conclusion that the neglect of the speed dependence of the turbine discharge can result in significant errors, especially when dealing with both low and high head machines.
Unsteady Flow About a Solid Cylinder Falling Through a Viscous Fluid Contained in a Vertical Tube
Authors: Shih C. C. , Yalamanchili Rao V. S.
Published: November 2010

This study is concerned with the unsteady flow field developed in a viscous fluid contained in a vertical tube by a solid cylinder of considerable length falling vertically from rest in the tube. Based on simplifying assumptions, the Navier-Stokes equations are linearized and reduced to a time-dependent one dimensional equation in cylindrical polar coordinates. A solution of the equation preceded by the determination of eigen values from boundary conditions peculiar to the problem of interest has yielded time-dependent velocity profiles across an axisymmetric cross-section of laminar flow in the annular space and other physical quantities related to the flow phenomena about the falling cylinder. Example problems were solved with the use of an electronic digital computer and the numerical results are presented in both tabular and graphical forms. In addition, a simple experiment of the flow system was performed and recorded on high speed movie films. The experimental results have verified reasonably well the theoretical results.
Effect of Normal Shock on Turbulent Boundary-Layer Parameters
Authors: Lumsdaine E. , Fathy A.
Published: November 2010

A simplified method based on the integration of the energy integral equation is used to investigate the changes in turbulent boundary layer parameters across a normal shock wave. The velocity distribution in the boundary layer is represented by a logarithmic velocity profile, thus allowing the prediction of incipient separation as well as the degree of separation. The present analysis is compared with an approximate method using the moment-of-momentum equation and the power law profile. The present method of predicting flow separation also shows good agreement with published experimental data.
An Examination of Eddy Viscosity Models for Turbulent Free Shear Flows
Authors: Elassar R. J. , Pandolfini P. P.
Published: November 2010

The boundary layer equations based on an eddy viscosity concept are solved numerically in the Crocco coordinate plane. A multilevel linear difference scheme is employed. Four different viscosity models are examined and the resulting solutions are compared. The empirical constants in the viscosity models are evaluated by comparing the calculated velocity profiles with experimental data in the similarity region.
Thermal Crack Propagation
Authors: Kassir M. K.
Published: November 2010

This study is concerned with the application of Griffith fracture theory to crack propagation induced by thermal means. The stress-strain field around an insulated crack, situated perpendicular to a uniform flow of heat in an elastic medium, is extracted from an isothermal configuration in which the crack surfaces are subjected to linear shear stresses. Similarly, a stress-free plane of discontinuity in heated (or cooled) solid gives rise to a pressurized crack in an otherwise traction-free solid. Adopting Griffith’s energy balance approach to brittle fracture, approximate expressions are computed for the critical temperature and critical temperature gradient pertaining to a flat elliptical crack embedded in a three-dimensional solid which is conducting heat in a steady-state manner. The results indicate that these critical parameters increase rapidly as the ratio of the major to minor semiaxes of the ellipse approaches unity.
Sensitivity of the Creep-Rupture Properties of Waspaloy Sheet to Sharp-Edged Notches in the Temperature Range 1000–1400 Deg F
Authors: Wilson D. J.
Published: November 2010

Time-dependent notch sensitivity of Waspaloy was observed at test temperatures from 1000 to 1300 deg F. Its occurrence in this range was dependent on the heat treatment. “Overaging” eliminated the notch sensitivity. Optimum combination of smooth and notched specimen strengths for material solution treated at 1975 deg F were obtained by aging 24 hr at 1550 deg F. Necessary conditions for time-dependent notch sensitivity were (i) the notch specimen loads had to be below the approximate 0.2 percent off set yield strength; and (ii) test data from smooth specimens had to indicate that small amounts of creep used up large fractions of creep-rupture life. No reasons were evident why these criteria will not prove applicable to other alloys.
The “Efficiency Transient Control” Concept for Optimal Load Control in Kaplan Turbine Hydroelectric Installations
Authors: Wozniak L.
Published: November 2010

In the case of Kaplan turbines the consideration of the efficiency parameter is critical from the control strategy synthesis viewpoint. As it is not essential in hydrosystem analysis, explicit efficiency parameter relationships have not been deployed to date for linearized Kaplan mathematical models used in control design. The “efficiency transient control” concept is developed herein. Basically, this approach purports to optimize transient behavior by controlling so as to decrease efficiency during the early transient portion of load rejection and likewise maximizing efficiency for the load acceptance case. For each perturbation this method leads to minimal flow change and, therefore, minimal over or under-pressures. As applied to a dominant gate with blade follow-up control scheme, the efficiency transient control concept prescribes the appropriate delay to be employed for optimum performance within the constraint of a follow-up device. Where the early transient deviates from best efficiency operation, a return to steady-state or “cam” operation occurs as the follow-up. The standard equations describing Kaplan turbine operation in linearized form by partial derivatives have been revised to include the efficiency parameter explicitly and now present a comprehensive and intelligible approach to Kaplan turbine control synthesis. The effect of the efficiency transient control upon system stability is analyzed and recommendations are made for desirable deployment. Application to nonlinear system operation is discussed. The efficiency transient control is compared with present day control schemes to assess their effectiveness. It is determined that a delay imposed upon the blades for the load-on case is suboptimal performancewise. The one-to-one gate-to-blade control is optimal in that case.
Effect of Rotation on Laminar Compressible Fluid Flow in a Vertical Cylinder
Authors: Hahn E. J.
Published: November 2010

Solutions are obtained for fully developed laminar flow of a compressible fluid through a rotating vertical cylinder. The results enable the velocity, friction loss, and pressure gradient to be easily calculated from corresponding incompressible flow solutions. It is shown that compressibility effects may be neglected completely over a practical range of operating conditions, such as encountered in centrifugal aerosol separators, enabling the flow analyses in these more complicated configurations to be justifiably simplified.
Turbulent Separation Analysis Ahead of a Step
Authors: Taulbee D. B. , Robertson J. M.
Published: November 2010

The general nature of the flow separation of a turbulent boundary layer ahead of an inward-projecting normal step is shown to be well predicted by a rotational flow analysis (frozen vorticity theory). The basis of this theory—that in the immediate vicinity of major wall contour changes the diffusive effects of viscosity and turbulence on the vorticity may be neglected and the flow field thus made amenable to rather simple analysis—is demonstrated and its application, via numerical iterative calculation, to prediction of the separation flow occurrence ahead of a step in terms of a given turbulent boundary layer is indicated. Good experimental verification of the predictions is found.
Effect of Temperature and Flange Support on Critical Pressure of Conical Acrylic Windows Under Short Term Pressure Loading
Authors: Stachiw J. D.
Published: November 2010

Temperature and the seating arrangement in the flange have a significant effect on the critical pressure of conical acrylic windows. Over 400 acrylic windows with 90 deg conical angle were used in this study to establish experimentally the relationship between thickness to minor diameter ratio (t/D), temperature, seating arrangement in the flange, and critical pressure under short term hydrostatic loading. The data indicates that utilizing 70 deg F as standard of comparison, there is, approximately 20 percent increase in critical short term pressure when 32 deg F, and 20 percent decrease when 90 deg F ambient temperatures are utilized, respectively. It was also found that the short term critical pressure of some conical acrylic windows is influenced by the seating arrangement in the flange. As a rule, an increase in the ratio of minor window diameter to minor flange opening diameter (D/Df) raised the short term critical pressure of windows with t/D ≥ 0.375 significantly. For windows with t/D < 0.375, it did not raise the critical pressure.
A Constitutive Equation for the Canine Anterior Cruciate Ligament
Authors: Bingham D. N. , DeHoff P. H.
Published: November 2010

A simplified constitutive equation is proposed to characterize the nonlinear viscoelastic behavior of the canine anterior cruciate ligament. The theory contains a single relaxation function which was measured experimentally by a series of uniaxial relaxation tests. To test the applicability of the theory, the experimentally determined function was used to attempt to predict the results of a special log-ramp test, as well as a constant strain-rate test. It was found that the simplified equation predicted stress results which were somewhat higher than experiment throughout much of the strain range tested.
Thermal Analysis and Design Considerations for a Dual-Beam Microwave Applicator for Hyperthermia Research
Authors: Hannemann R. J. , Robinson J. E.
Published: November 2010

Hyperthermia is a promising potential modality for cancer therapy and consequently much research into the physiological effects of tumor heating is currently being undertaken. Crucial to these biological experiments and to the utlimate application of hyper-thermia-inducing devices is the ability to predict and control the resultant thermal fields. A candidate mechanism for the deposition of thermal energy at depth in tissue is the use of multiple focused microwave beams. The present paper describes thermal analysis and design calculations recently completed for an experimental dual-beam microwave applicator system currently being used in hyperthermia research. Limited comparisons to experimental observations are included.