bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of Slender Tapered Beams With Internal or External Axial Flow—Part 1: Theory
Authors: Hannoyer M. J. , Paidoussis M. P.
Published: November 2010

This paper develops a general theory for the dynamics of slender, nonuniform axisymmetric beams subjected to either internal or external flow, or to both simultaneously. The effect of the boundary layer of the external flow is taken into account in the formulation. Typical solutions of the equations of motion are presented for cantilevered conical beams in external flow and for beams with a conical internal flow passage. Such systems lose stability at sufficiently high flow velocity, internal or external, either by flutter or by buckling. The effect of several parameters is investigated. For internal flow, the internal and external shape, whether uniform or conical, and the density of the surrounding fluid have sometimes unexpected effects on stability; e.g., tubular beams lose stability at lower internal flow when immersed in water than when in air. For external flow the effects of conicity, free end shape and boundary-layer thickness are investigated; the latter has a strong stabilizing influence, such that simple theory neglecting this effect results in serious error.
On H. Hencky’s Approximate Strain-Energy Function for Moderate Deformations
Authors: Anand L.
Published: November 2010

It is shown that the classical strain-energy function of infinitesimal isotropic elasticity is in good agreement with experiment for a wide class of materials for moderately large deformations, provided the infinitesimal strain measure occurring in the strain-energy function is replaced by the Hencky or logarithmic measure of finite strain.
Solidification of a Sphere: The Effects of Thermal Contraction and Density Change Upon Freezing
Authors: Forgac J. M. , Schur T. P. , Angus J. C.
Published: November 2010

The stress and internal pressure in a solidifying sphere are calculated as a function of heat transfer rate and the density change upon freezing. A numerical solution to the heat transfer problem and a linear isotropic thermoelastic model for the solid are used to describe the solidification process. Results are presented for a model material with typical metallic properties. Heat transfer effects alone cause compression and the density increase upon freezing by itself produces tension within the liquid core. Thermal compression effects can dominate during the early stages of solidification, but only at relatively high rates of heat transfer. The effect of the density change dominates in the later stages and the liquid core goes into tension. It is unlikely that sustained high pressures can be generated within solidifying spheres. The model indicates regimes of low stress where the solid shell may be expected to remain intact during the initial stages of solidification.
Compressible Boundary-Layer Swirling Flow in a Nozzle and a Diffuser With Highly Cooled Wall
Authors: Kumari M. , Nath G.
Published: November 2010

The steady laminar compressible boundary-layer swirling flow with variable gas properties and mass transfer through a conical nozzle, and a diffuser with a highly cooled wall has been studied. The partial differential equations governing the nonsimilar flow have been transformed to a system of coordinates using modified Lees transformation. The resulting equations are transformed into coordinates having finite ranges by means of a transformation which maps an infinite region into a finite region. The ensuing equations are then solved numerically using an implicit finite-difference scheme. The results indicate that the variation of the density-viscosity product across the boundary layer and mass transfer have strong effect on the skin friction and heat transfer. Separationless flow along the entire length of the diffuser can be obtained by applying suction. The results are found to be in good agreement with those of the local nonsimilarity method but they differ appreciably from those of the local similarity method.
Application of Hamilton’s Principle to Large Deformation and Flow Problems
Authors: Dost S. , Tabarrok B.
Published: November 2010

Application of Hamilton’s principle to large deformation and flow problems is examined with an emphasis on derivation of the Eulerian equations of motion as stationary conditions of the functional. It is shown that Eulerian variations can be admitted in Hamilton’s functional providing certain side constraints are imposed. Finally the Complementary Energy principle is briefly examined and difficulties in admitting Eulerian variations in this principle are discussed.
Dynamic Buckling of a Damped Externally Pressurized Imperfect Cylindrical Shell
Authors: Lockhart D. F.
Published: November 2010

The dynamic buckling of a finite damped imperfect circular cylindrical shell which is subjected to step-loading in the form of lateral or hydrostatic pressure is examined by means of a perturbation method. The imperfection is assumed to be small. An asymptotic expression for the dynamic buckling load is obtained in terms of the damping coefficient and the Fourier component of the imperfection in the shape of the classical buckling mode. A simple relation which is independent of the imperfection is then obtained between the static and dynamic buckling loads.
The Elastic Field in a Half Space Due to Ellipsoidal Inclusions With Uniform Dilatational Eigenstrains
Authors: Seo K. , Mura T.
Published: November 2010

The elastic stress field caused by an ellipsoidal inclusion with uniform dilatational eigenstrains is investigated for a semi-infinite solid. The result is expressed in terms of derivatives of elliptic integrals. Numerical examples are given to show the effect of the free surface with parameters of depth from the surface and shapes of the inclusion.
A Simplified Method to Account for Plastic Rate Sensitivity With Large Deformations
Authors: Perrone N. , Bhadra P.
Published: November 2010

A string supported impulsively loaded mass is used to study large deformation rate sensitivity effects where membrane action is dominant. It is found that an overall correction factor can be devised using physical properties associated with the average strain rate. Maximum strain rate occurs with a velocity field corresponding to the deformation state wherein half the initial kinetic energy has been dissipated. (If V0 is initial velocity, V0/2 is associated with maximum strain rate.) Exact and approximate solutions for a broad range of parameters serve to illustrate and verify the procedure. A discussion is presented to show how the same methodology could also be applied via a modal approach to an arbitrary three-dimensional structure undergoing large deformations, if the primary mechanism for energy absorption is from membrane action.
On the Strength Anisotropy of Bone and Wood
Authors: Cowin S. C.
Published: November 2010

Formulas for the tensile, compressive, and shear strengths along an axis off the grain axis of a material with orthotropic symmetry are derived from the quadratic form of the Tsai-Wu strength theory. The results are compared with some shear strength data on wood and they are applied to data on human femoral bone and bovine Haversian bone. A strength criterion consistent with the Tsai-Wu theory and with the existing experimental strength data on bone is identified.
Alternate Exact Equations for the Inextensional Deformation of Arbitrary, Quadrilateral, and Triangular Plates
Authors: Simmonds J. G. , Libai A.
Published: November 2010

Previously, a set of 9 exact differential equations was derived for the inextensional deformation of a plate bounded by two straight edges and two arbitrary curves. One straight edge is built-in. The other moves rigidly and is subject to a force and couple. The curved edges are stress-free. If the plate twists as it deforms, then, as shown herein, the 9 equations may be replaced by 7. The equations are written in a dimensionless form allowing a ready comparison with Mansfield’s theory that assumes small but finite angles of rotation. If the end load is a couple only, then an independent set of 5 equations emerges. These reduce to 4 for a quadrilateral plate. A numerical example compares the prediction of the exact equations against those of Mansfield. For triangular plates under tip forces only, an alternate, better conditioned, set of 9 differential equations is derived, and the behavior of the solutions near the tip is analyzed.
Lateral Dynamics and Stability of the Skateboard
Authors: Hubbard M.
Published: November 2010

The natural lateral dynamic behavior of a skateboard is described in the absence of rider control. The effects of vehicle and rider parameters are investigated and stability criteria are derived in terms of these parameters. It is shown that for certain parameter values a simple one-degree-of-freedom vehicle model predicts a critical speed above which inertia effects can stabilize the roll motion, and that the frequency of roll oscillations is a function of forward speed. A more complicated two-degree-of-freedom vehicle model, including independent roll of both the board and of the rider, is also derived and is shown to have the possibility of speed stabilization as well. Experimental validation of the first theory is included.
Thermodynamic Effects on Desinent Cavitation on Hemispherical Nosed Bodies in Water at Temperatures From 80 Deg F to 260 Deg F
Authors: Holl J. W. , Kornhauser A. L.
Published: November 2010

The theoretical analysis and experiments are presented for desinent (limited) cavitation on hemispherical nosed bodies in water at temperatures from 80 to 260 deg F. The models were 1/4 in. and 1/2 in. in diameter and were tested at velocities of 44, 76, and 132 fps in the NASA cavitation tunnel at The Pennsylvania State University. The theoretical model which most closely agrees with experiment is the isothermal case for surface nuclei. Arguments are presented which tend to support the validity of this result.
A Synthesis Technique for Nonlinear Control Systems Using a Frequency Domain Stability Criterion
Authors: Garg Devendra P. , Auslander David , Rabins M. J.
Published: November 2010

This paper deals with a design approach to the synthesis of controllers for nonlinear control systems. The method proposed herein uses the frequency domain circle condition as a sufficiency criterion for insuring absolute stability. While the theory involved is well known, its application as a design tool has not yet been fully appreciated. A major aim of this paper is to indicate means of employing this new theory by use of classical frequency-domain techniques. The circle of nonlinearity from the Nyquist plane is transferred as a region onto the logarithmic gain-phase versus frequency plane using a simple transformation. A system controller or compensator can now be designed, straightforwardly without trial and error, by using the explicit frequency scale. Parameter combinations for system controllers yielding absolute stability can be obtained in a parameter plane or parameter space depending upon compensator configuration. The entire procedure is digital computer oriented but can be accomplished by paper and pencil techniques. Several numerical examples, along with hybrid computer corroboration, illustrate the procedure.
An Approximate Method of State Estimation for Nonlinear Dynamical Systems
Authors: Sunahara Y.
Published: November 2010

In this paper, a method of stochastic linearization is demonstrated for the purpose of establishing an approximate approach to solve filtering problems of nonlinear stochastic systems in the Markovian framework. The principal line of attack is to expand the nonlinear function into a certain linear function with coefficients which are determined under the minimal squared error criterion. The linearized function is specified by the coefficients dependent on both the state estimate and the error covariance. Thus, a method is given for the simultaneous treatments of approximate structure of state estimator dynamics and of running evaluation of the error covariance through the linearized procedure. Comparative discussions on the other filter structures are also given, including quantitative aspects of sample path behaviors obtained by digital simulation studies.
Flow Past a Right Circular Cylinder in a Rotating Frame
Authors: Boyer D. L.
Published: November 2010

The flow of a homogeneous incompressible fluid past a right circular cylinder in a rotating frame is considered; the axis of the cylinder is taken parallel to the axis of rotation while the cylinder is bounded above and below by two infinite parallel flat plates. A series of experiments are presented which qualitatively describe the flow for an aspect ratio of 1.0 and Rossby and Ekman number ranges of (10)−2 < Ro < 1.0 and (10)−4 < E < (10)−3, respectively. The flow regimes differ significantly from those occurring in nonrotating systems.
A Finite-Difference Method for Calculating Compressible Laminar and Turbulent Boundary Layers
Authors: Cebeci T. , Smith A. M. O.
Published: November 2010

This paper presents a finite-difference method for solving laminar and turbulent-boundary-layer equations for incompressible and compressible flows about two-dimensional and axisymmetric bodies and contains a thorough evaluation of its accuracy and computation-time characteristics. The Reynolds shear-stress term is eliminated by an eddy-viscosity concept, and the time mean of the product of fluctuating velocity and temperature appearing in the energy equation is eliminated by an eddy-conductivity concept. The turbulent boundary layer is regarded as a composite layer consisting of inner and outer regions, for which separate expressions for eddy viscosity are used. The eddy-conductivity term is lumped into a “turbulent” Prandtl number that is currently assumed to be constant. The method has been programed on the IBM 360/65, and its accuracy has been investigated for a large number of flows by comparing the computed solutions with the solutions obtained by analytical methods, as well as with solutions obtained by other numerical methods. On the basis of these comparisons, it can be said that the present method is quite accurate and satisfactory for most laminar and turbulent flows. The computation time is also quite small. In general, a typical flow, either laminar or turbulent, consists of about twenty x-stations. The computation time per station is about one second for an incompressible laminar flow and about two to three seconds for an incompressible turbulent flow on the IBM 360/65. Solution of energy equation in either laminar or turbulent flows increases the computation time about one second per station.
Nuclei and Cavitation
Authors: Holl J. William
Published: November 2010

This paper is a review of existing knowledge on cavitation nuclei. The lack of significant tensions in ordinary liquids is due to so-called weak spots or cavitation nuclei. The various forms which have been proposed for nuclei are gas bubbles, gas in a crevice, gas bubble with organic skin, and a hydrophobic solid. The stability argument leading to the postulation of the Harvey model is reviewed. Aspects of bubble growth are considered and it is shown that bubbles having different initial sizes will undergo vaporous cavitation at different liquid tensions. The three modes of growth, namely vaporous, pseudo, and gaseous are presented and implications concerning the interpretation of data are considered. The question of the source of nuclei and implications concerning scale effects are made. The measurement of nuclei is considered together with experiments on the effect of gas content on incipient cavitation.
A Field Method of Determining Gas Turbine Meter Performance
Authors: Lee W. F. Z. , Evans H. J.
Published: November 2010

The need for a simple and inexpensive method for field checking gas turbine meters exists. One such method called the “spin test” is described in this paper. The relationship between the change of “rotor coast time” of the spin test and the change of meter accuracy due to change of mechanical friction is formulated. Experimental results on two different 6-in. gas turbine meters are presented and show good agreement with analytical results.
Mechanism of Slug Formation in Horizontal Two-Phase Flow
Authors: Kordyban E. S. , Ranov T.
Published: November 2010

It is proposed in this work that the transition to slug flow occurs due to Kelvin-Helmholtz instability, which, in this case, is enhanced by the proximity of the upper wall and becomes wave-amplitude dependent. Since the surface waves possess a limiting amplitude, the transition can be predicted by examining whether the highest possible waves are unstable. The theoretical prediction is in good agreement with the authors’ experimental results. It also agrees reasonably well with Baker’s and Schicht’s flow pattern charts for strictly horizontal channels, but it exhibits large differences when the channels deviate somewhat from the horizontal.
The Effects of an Annular Fluid on the Vibrations of a Long Rotor, Part 1—Theory
Authors: Fritz R. J.
Published: November 2010

Analysis and tests were made to investigate the hydrodynamic mass and damping effects of a liquid in a thin annulus surrounding a vibrating rotor. The analytical results are described in this report and the test results in Part 2. The analysis determines the fluid forces for the general case of a vibrating rotor. Vibrational amplitudes and the limits of dynamic stability are then determined for a constant-speed rotor excited by unbalance. Fluid flow was assumed incompressible and tangential and to be in the Taylor vortex regime or in the turbulent regime. The Taylor vortex regime is considered a natural convection process resulting from centrifugal force gradients, while the turbulent regime is a forced convection process. As a result, annular flow around a rotor is considered an inherent combination of forced and natural convection. Fluid damping is estimated for each process separately and for the case where the vortex and turbulent process are predicted to occur simultaneously.
Flow Separation and Reattachment in Confined Jet Mixing
Authors: Exley John T. , Brighton John A.
Published: November 2010

An experimental and theoretical investigation was conducted to study flow separation and reattachment for a confined axisymmetric jet. The fluid was air with an initially uniform velocity jet mixing with an initially uniform (but lower velocity) secondary flow. Both streams were at the same temperature and mixed in a constant-diameter duct. The location of the points of separation and reattachment and the line of zero velocity were determined by injecting smoke into the flow. Measurements were made over a wide range of diameter ratios (nozzle diameter to mixing tube diameter) and velocity ratios (jet velocity to secondary velocity at the inlet). The separation point was strongly affected by the velocity ratio—moving upstream with an increase in velocity ratio. Reattachment, however, was only slightly affected by velocity ratio. A single parameter, such as the Curtet number, was found to be inadequate in describing separation and reattachment over all diameter ratio and velocity ratio conditions.
A Theoretical Approach to Creep Deformation During Intermittent Load
Authors: Lagneborg R.
Published: November 2010

The influence of intermittent loading on creep deformation has been examined in terms of the recovery creep theory. It has been shown that according to this theory a material exposed to cyclic stresses of the same sign always creeps at a rate that is larger than the average of the steady state creep rates at the various stresses. Numerical computations have been performed in order to show how this accelerated strain depends on the applied stress and the time of the stress cycle.
A Study of Contrarotating Turbines Based on Design Efficiency
Authors: Ozgur C. , Nathan G. K.
Published: November 2010

In this paper the efficiency of an axial flow contrarotating turbine is expressed in terms of two dimensionless parameters. From this expression the efficiency of a single runner tubular turbine is obtained by considering it as a special case of the first arrangement, i.e., having one runner stationary. The effects and the interactions of various parameters on the optimum efficiency for both cases are analyzed and equations for the maximum efficiencies for a given flow coefficient are established. The maximum efficiency under a fixed specific speed is also investigated. The possibility of extension to the three dimensional case is indicated. The comparison of both types of turbines with and without limitations shows that on the basis of optimum efficiency contrarotating turbines are more favorable than single runner turbines for low head installations.
The Natural Frequencies of Two Spherical Bubbles Oscillating in Water
Authors: Shima A.
Published: November 2010

The natural frequencies of two spherical bubbles, as they oscillate near each other in water, was theoretically studied, by taking account of surface tension, and on the assumption of the gas in the bubbles following the law of adiabatic change. As a result, the present solution includes these solutions of Minneart, Richardson and Neppiras and Noltingk as particular cases.
The Dispersion of Matter in Turbulent Pipe Flows
Authors: Atesmen K. M. , Baldwin L. V. , Haberstroh R. D.
Published: November 2010

The dispersion of matter in fully developed turbulent pipe flow is described by the transient diffusion equation with an eddy diffusivity approximation. G. I. Taylor’s [16] analysis for asymptotically long dispersion times started a revival of publications on this problem. The moment method of Aris [2], which is well suited to computer methods, is used to solve the mass conservation equation for dispersion near the injection source. The governing equations are converted to a tractable system of equations which is solved mainly by numerical methods with the aid of a digital computer, for the zeroth, first, second, third, and fourth moment of the longitudinal concentration distribution. The utility of the moment method is enhanced by use of Hermite polynomials to express the longitudinal concentration distributions. The present results agree with the asymptotic predictions of Taylor for long dispersion times. The computational convenience of the suggested solution is demonstrated for specific examples where experimental data are available.
Potential Flow Past a Group of Circular Cylinders
Authors: Dalton C. , Helfinstine R. A.
Published: November 2010

The problem of an accelerating potential flow past a group of stationary circular cylinders is considered using the method of images. The problem is formulated so that the number and location of the cylinders is arbitrary so long as there is no overlap between adjacent cylinders. Inertial and lift coefficients are determined for several different cylinder arrangements. The inertial coefficient for a cylinder can vary in either direction from its single-cylinder value of 2.0. The controlling factors on this variation are the relative geometric position of the cylinder within the group and its distance from its neighbors. These same factors determine, as is expected, the lift coefficient values. In two example configurations, there is even a drag-type force generated on an individual cylinder in the potential flow.
Mechanical Behavior of Uniaxially Loaded Multilayered Cylindrical Composites
Authors: Hamilton C. H. , Hecker S. S. , Ebert L. J.
Published: November 2010

An analytical model was developed to predict the mechanical response to axial loading of oriented fiber composite materials containing a third (dissimilar) material at the fiber-matrix interface. The model approximated the fiber composite geometry by three concentric, but integral, cylinders. Both a totally elastic and an elastic-plastic analysis of the three-component cylinder demonstrated that transverse stresses, with the signs and magnitudes depending upon the elastic and plastic characteristics of the components, developed during axial loading. Tensile transverse stresses, which could drastically reduce the axial properties of the composite if a brittle layer existed at the interface, were shown to result from various combinations of component properties. The internal stresses predicted for the composite model were verified experimentally by testing three-component composite cylinders of maraging steel-copper-maraging steel and Berylco-copper-Berylco in tension.
Yield Criteria and the Bauschinger Effect for a Plastic Solid
Authors: Dubey R. N. , Hillier M. J.
Published: November 2010

A general yield criterion and flow rule based on invariance principles is applied to the case of an ideal strain hardening solid having principal axes of anisotropy and a significant Bauschinger effect.
The Fluid Mechanics of Multiple-Venturi Systems and Their Application to Flow-Rate Metering
Authors: Klomp E. D. , Sovran G.
Published: November 2010

The concept of a multiple-venturi system is applied to the design of a flow-rate meter. This meter type has the capability of offering a high signal-to-loss ratio over a broad flow range. Its internal fluid mechanics are discussed with a view toward design optimization. Experimental results are reported and analyzed for a three-element meter.
Computerized Evaluations of the Relative Abilities of Seven Time-Temperature Parameters to Correlate and Extrapolate Nickel Alloy Stress-Rupture Data
Authors: Raut P. K. , Clough W. R.
Published: November 2010

A total of 31 stress-rupture data sets for 28 different nickel-base alloys, including 1153 individual test results, have been treated by graphical methods and computer programs to allow determinations of the relative abilities of Larson-Miller, Manson-Haferd, Sherby-Dorn, Goldhoff-Sherby, Manson-Succop, Conrad and Korchynsky parameters to correlate and extrapolate data. For the correlation of all data the Goldhoff-Sherby and Manson-Haferd methods are attractive, while for extrapolation to longer times some superiority of the Manson-Haferd and Manson-Succop parameters is demonstrated. Overall use of a third order polynomial approximation to Manson-Haferd master curves is recommended, as is the avoidance of external extrapolation. Results are primarily based on modified and original computer programs and standard statistical treatments of data.
A Freeman Scholar Lecture: The Effect of Additives on Fluid Friction
Authors: Hoyt J. W.
Published: November 2010

The turbulent frictional resistance of dilute polymer solutions can be as low as one-quarter that of the pure solvent. The reduction of drag can be associated with polymer properties and the hydrodynamics of the flow. This review illustrates the key concepts in hydrodynamics, polymer chemistry, and rheology which apply to polymer drag reduction. The effect of parts-per-million polymer concentrations on laminar-turbulent transition, boundary-layer properties and turbulent frictional resistance in pipe flow and along flat plates is emphasized, using experimental data from current literature. Industrial, fire-fighting, marine, and biological applications are discussed.
A Freeman Scholar Lecture: Desalination: Some Fluid Mechanical Problems
Authors: Probstein R. F.
Published: November 2010

Despite the fact that the world’s need for desalinated water is becoming more urgent, the ability to economically desalinate on a large scale still remains a goal rather than a reality. The present review examines distillation, freezing, electrodialysis, and reverse osmosis which together account for essentially all of the installed desalination capacity. Although distillation is by far the most widely employed system, emphasis is placed on the other three methods because of their potential. It is shown that for each process one or more of the critical technical problems which lead to increased fresh water costs is associated with a fluid mechanical phenomenon. The review attempts to present the critical fluid engineering problems, and where possible the solutions and their consequences in relation to the goal of obtaining desalted water economically.
A Simple Theory for the Two-Dimensional Compressible Turbulent Boundary Layer
Authors: White F. M. , Christoph G. H.
Published: November 2010

A new approach is proposed for analyzing the compressible turbulent boundary layer with arbitrary pressure gradient. Utilizing a compressible law-of-the-wall and a Crocco energy approximation, the new theory integrates the momentum equation across the boundary layer in terms of inner variables only. The result is a single first-order ordinary differential equation for skin friction, devoid of integral thicknesses and shape factors. When analyzed for flat plate flow, this new equation has an exact solution apparently superior in accuracy to any other flat plate theory (Table 1). The new equation also agrees well with supersonic skin friction data in both favorable and adverse pressure gradients. The new theory contains an explicit separation criterion and is the simplest and possibly most accurate existing analysis for compressible turbulent flow.
Second Order Boundary Layer Solutions on a Curved Surface
Authors: Van Tassell W. F. , Taulbee D. B.
Published: November 2010

Solutions of the second order longitudinal curvature boundary layer equations near the stagnation point of a two-dimensional circular cylinder are presented. Four cases corresponding to 1 first order locally similar solutions, 2 first order nonsimilar solutions, 3 second order locally similar solutions, and 4 second order nonsimilar solutions are considered. For each of the four cases, results for four different altitudes are given. The only second order effect considered is longitudinal curvature. Based on the numerical results, it is concluded that similarity and curvature assumptions can alter the skin friction calculations significantly. The heat transfer calculations are much less sensitive to the various assumptions, at least for the cases studied in this paper.
Large Floating Platform Technology: A Review
Authors: Bedore R. L.
Published: November 2010

The purpose of this study was to review all material relevant to the design, construction, and operation of a large floating columnar platform made of ferroconcrete. Existing platforms, motion analysis, anchoring, powering, assembly and ferroconcrete are discussed. The study indicates that ferroconcrete platforms can be built and that electric power generation sites may be the first application of the idea.
An Experimental Study of Compressible Flow Through Convergent-Conical Nozzles, Including a Comparison With Theoretical Results
Authors: Thornock R. L. , Brown E. F.
Published: November 2010

Despite the widespread use of convergent-conical nozzles as propulsion nozzles in turbojet aircraft, little attention has been given to the effect of nozzle shape on their propulsive performance. This paper presents the results of an experimental investigation in which the effect of nozzle angle on the internal characteristics of the flow field and on the propulsive performance of convergent conical nozzles was investigated. In addition, a theoretical solution is described which was developed as a part of this investigation. Fifteen, twenty-five, and forty-degree nozzles were tested at pressure ratios from 1.4 to 7.0. Measurements were made of the nozzle discharge coefficient, thrust coefficient, local flow angle, and wall static pressure. The properties of the internal flow field were seen to be affected by the nozzle angle and at pressure ratios less than the choked pressure ratio by the pressure ratio as well. The results of the theoretical analysis substantiate this behavior and are in reasonable agreement with the experimental data.
A Photographic Study of the Effect of an Air Bubble on the Growth and Collapse of a Vapor Bubble Near a Surface
Authors: Smith R. H. , Mesler R. B.
Published: November 2010

Interaction of an individual vapor bubble formed by a spark gap in water at room temperature with a neighboring air bubble, such as could have significance in cavitation, was investigated using high speed photography. Air bubbles were located both on and far from boundaries. An air bubble located on the solid boundary was able to protect the surface from damage. Two effects of the interaction which appeared to be important in the damage prevention were energy transfer from the vapor bubble to the gas bubble and repulsion of the vapor bubble by the gas bubble. Gas bubbles far from boundaries absorbed less energy and had less repulsive effect than those on solid boundaries.
The Biomechanical Function of the Collagen Fibril Ultrastructure of Articular Cartilage
Authors: Askew M. J. , Mow V. C.
Published: November 2010

An inhomogeneous, layered, anisotropic, continuum model of the in-situ articular cartilage-on-bone structure is developed. The model, based on the collagen fibril ultra-structure of the tissue, incorporates an anisotropic (transversely isotropic) layer modeling the superficial tangential zone. The stresses, strains and displacements generated in this model by a static, axisymmetric, parabolically distributed shear-free surface load are determined, using integral transforms and numerical methods. The predicted deformation under the modeled normal physiological loading condition is examined along with deformation changes resulting from abnormal changes in loading geometry and material properties. The results of this analysis of the modeled, layered, inhomogeneous structure, when extrapolated to normal in-vivo conditions, imply that the articular surface is not exposed to continuum tensile stresses, but may be predisposed to possible long term damage due to fatigue by tensile strains. Abnormal decreases in the loaded area of the joint, perhaps due to loss of congruency or degeneration in the joint, cause changes in the magnitude and in the character of the deformational quantities that are detrimental to the long-term survival of the tissue.
Orthogonal Machining of Bone
Authors: Wiggins K. L. , Malkin S.
Published: November 2010

An investigation is described of the mechanics of orthogonal machining of bone. Experimental results are presented for the machining forces and specific energies for various cutting orientations, rake angles, and depths of cut. From microscopic observations on sections taken through the cutting zone, the chip formation process is seen to occur by a series of discrete fractures. A simple model is proposed to qualitatively describe the mechanics of chip formation. The energy expended by the cutting process under a wide variety of conditions is found to increase linearly with the surface area generated on the chip fragments, which is a further indication that chip formation during cutting of bone occurs by fracture.
Graphical Interpretation of the Solution to the Redundant Problem in Biomechanics
Authors: Chao E. Y. , An K. N.
Published: November 2010

Force analysis of musculoskeletal joint systems is a redundant problem since the number of unknowns exceeds the number of equilibrium and constraint equations. Such a problem has been analyzed previously by the method of permutation/combination and by optimization technique. This paper combines both methods and discusses the results in the light of a graphical presentation from which unique and nonunique solutions to the problem are elaborated. When the applied load is nominal, multiple solutions are possible to meet the functional requirements. However, under maximum strength, unique solution exists because the redundant muscles reach their physiological limits.
Constitutive Equation of Lung Tissue Elasticity
Authors: Vawter D. L. , Fung Y. C. , West J. B.
Published: November 2010

A constitutive equation for the lung tissue elasticity is formulated under the hypotheses of a simplified alveolar geometry and a pseudo-strain-energy function for the interalveolar septa. The resulting equation contains four material constants. The theoretical result has been tested against published data on uniaxial and triaxial loadings, and is tested critically here with respect to new experimental results on biaxial loading. Comparison between theory and experiments shows that a general agreement is obtained in an approximate sense. The model fits our biaxial experimental data with most correlation coefficients above 0.995. Some details not predicted by the theory are discussed. Since the theory is derived for triaxial loading and the biaxial test is a severe one, the formula should be applicable to the triaxial case at least to the same degree of approximation. The form of the theoretical formula is convenient to use in analytic studies of lung mechanics. Additional key words: mechanical behavior of the lung; stress-strain relationship; strain energy; alveolus model; distortion; interdependence; pressure volume curves.
Transient Temperature Distributions in an Infinite, Perfused Medium due to a Time-Dependent, Spherical Heat Source
Authors: Jain R. K.
Published: November 2010

Analytical expressions for transient temperature distributions within a two-zone heating probe and the surrounding infinite, isotropic, homogeneous, perfused medium are obtained. The periphery of the probe simulates the stagnant blood layer which usually forms around a thermistor probe if it is inserted into the tissue. A procedure to estimate thermal properties of tissues in vivo using these results is also outlined.
Spectral and Temporal Characteristics of Post-Stenotic Turbulent Wall Pressure Fluctuations
Authors: Pitts W. H. , Dewey C. F.
Published: November 2010

The power spectral density of turbulent wall pressure fluctuations was measured in a tube downstream of a model arterial constriction. The flow parameters were varied from steady flow to conditions simulating human arterial pulsatile flow. Within the experimental uncertainty (±10 percent in characteristic turbulent frequency, fo, and ±25 percent in absolute rms pressure fluctuation amplitude), turbulent flow at the peak of systole produces wall pressure fluctuations identical to those of a steady flow at the same Reynolds number.
Time Progression of Hemolysis of Erythrocyte Populations Exposed to Supraphysiological Temperatures
Authors: Moussa N. A. , Tell E. N. , Cravalho E. G.
Published: November 2010

Populations of erythrocytes in solution were heated “instantaneously” to and maintained at temperatures in the range of 44 to 60°C on a microscope stage specifically designed for this purpose. Simultaneously, the visually observed hemolysis-time history of these cells was measured. The results were successfully correlated on the basis of two models: 1) a kinetic scheme assuming two sequential, first-order reactions by which the cells are first reversibly altered and then irreversibly damaged; and 2) a statistical model for which the number of cells that are damaged at each instant is assumed to be normally distributed. From the experimental data the rate constants for the two reactions in the kinetic model were determined and were found to have an Arrhenius dependence on temperature. By applying the statistical model to the data, we were able to determine the mean and standard deviation of the distribution curve for this model. The logarithms of these latter two parameters vary with temperature in a linear fashion.
Thermography as a Means of Blood Perfusion Measurement
Authors: Francis J. E. , Roggli R. , Love T. J. , Robinson C. P.
Published: November 2010

The scanning infrared camera has been used to verify an analytical model relating blood perfusion rate to skin temperature. The blood perfusion rates were measured with both the mercury strain gage and the volume plethysmograph on the human forearm. Thermograms were taken of the forearm and temperature measured using an optical densitometer. Comparison of the volume plethysmograph with the strain gage, and the thermograms with the strain gage indicate thermography to be a useful means of measuring blood flow. Thermography has the advantages of being noninvasive and can be used to measure blood perfusion in parts of the body not easily monitored with occlusive techniques.
An Experimental and Theoretical Investigation of Hypothermia in Dogs
Authors: Mauck G. W. , Smith C. R. , Incropera F. P. , Weirich W. E.
Published: November 2010

A technique for post surgical rewarming from clinical hypothermia, which utilizes a thoracic flush with heated saline solution, has been investigated experimentally and theoretically. The rewarming technique was used in conjunction with surface cooling for eighteen separate experiments using mongrel dogs, with the thermal response of the animals determined from thermocouple measurements at twelve strategic locations. Utilizing these measurements, temperature histories were established for the animals, from which representative cooling and rewarming rates have been determined. The rectal temperature was found to provide a suitable clinical reference temperature for monitoring the level of hypothermia, and the rewarming rates (from 10 to 22° C/hr) compare favorably with those obtained by other investigators using surface and extracorporeal rewarming methods. Reasonable agreement was obtained between the measured temperature histories and theoretical predictions obtained using a simple lumped parameter heat transfer model.
Pseudo Bond Graphs for Thermal Energy Transport
Authors: Karnopp Dean
Published: November 2010

Bond graphs have been shown to be useful in the modeling of a wide variety of physical dynamic systems, but open systems in which energy is transported across boundaries with mass flow have never been modeled as elegantly as fixed mass systems and their analogs. In this paper a bond graph, building block approach is outlined which allows most of the conceptual and practical advantages of normal bond graph techniques to be retained for systems in which thermal energy transported by a flowing fluid is important. Practical applications include the dynamic modeling of heating and cooling systems involving air and water. The method allows the imposition of a constant causal scheme independent upon the direction of fluid flow. The result is a pseudo bond graph since the use of temperature and heat flow as effort and flow means that the product of effort and flow is not power as in normal bond graphs.
Analysis of Leg Loading in Snow Skiing
Authors: Hull M. L. , Mote C. D.
Published: November 2010

The complete excitation between the boot and ski was measured during skiing. Data from strain-gage force transducers mounted inside the test ski were FM transmitted to a receiving station about 3 km distant. Three skiing maneuvers (snowplow, stem christiana, parallel christiana) were tested and data from authentic falls were also recorded. Data were plotted in real-time and analyzed by digital computer. The loading histories reveal that the nonstationary loading is related to maneuver type. Torsion and bending component amplitudes, measured at the boot sole, are approximately equal to the static tibia ultimate strength in bending and torsion during both elementary skiing maneuvers and falls. In these high amplitude loading situations the skier was not injured. Data were analyzed for spectral content by the Fast Fourier Transform (FFT). Results show a 3.5 Hz cutoff frequency common to all load components and maneuvers. 3.5 Hz is a reasonable corner frequency for the human controller. Results suggest that below 3.5 Hz the skiing excitation is primarily muscle induced while above 3.5 Hz the excitation is due to ski-snow interaction.
Stability of a Vehicle on a Multispan Simply Supported Guideway
Authors: Chung Y. I. , Genin J.
Published: November 2010

The dynamic response of a vehicle, with a conventional suspension system, traversing a multispan simply supported guideway system is studied parametrically. The steady state response of the system and conditions for dynamic instabilities are presented for the case where the ratio of vehicle length/span length is small. Using vehicle heave acceleration and maximum guideway deflection as performance criteria, it is shown that the interactive inertial effect is significant, even at relatively low traversing speeds.
Application of Optimal Preview Control to Power Plant Cooling Systems
Authors: Gunewardana D. R. , Tomizuka M. , Auslander D. M.
Published: November 2010

This paper deals with the application of dynamic control to cooling systems of power plants. The operation of heat dispersal systems with control can result in a saving of power and cooling water. The performance of all cooling systems depends, mainly, upon the ambient conditions and the heat load to be dissipated. Hence, a control scheme that makes use of information obtained by previewing the weather and load conditions, i.e., preview control, is ideally suited for this problem. An iterative procedure is presented for determining the optimal preview control policy for a dynamical system whose dynamics vary depending upon the mode of operation that the controller selects. The algorithm is applied to two types of cooling systems: one consisting of a spray pond and a natural draft wet cooling tower, and the other consisting of a spray pond and a dry cooling tower. The preview control scheme is shown to be a substantial improvement over the uncontrolled case.
On the Order of a Physical System Model
Authors: Karnopp Dean
Published: November 2010

The idea that the order of a given model of a physical system is equal to the number of independent energy storage elements is often correct if all types of dependence are taken into account. However, the choice of output variables also affects the minimum order required. An example is given which is 4th, 3rd, or 2nd order depending upon which physical variables are required as output variables.
State Variables and Pseudo Bond Graphs for Compressible Thermofluid Systems
Authors: Karnopp Dean
Published: November 2010

Bond graphs aid in the creation of lumped parameter models for a wide variety of physical and biological systems but have proved less useful when it is desired to use control volume methods and a variable amount of matter is enclosed by the volume. In the present paper, a class of pseudo bond graphs is presented which handles control volume problems in a natural way and which retains most of the advantages of true bond graphs. The effort and flow variables do not, however, represent complementary power variables and thus many of the multiport element constitutive laws do not obey symmetry conditions based upon stored energy state functions. On the other hand, the general structure of the model is quite clearly shown and the causality of component interactions can be compactly and clearly shown just as in true bond graphs.
Controlled Dynamic Characteristics of Ferromagnetic Vehicle Suspensions Providing Simultaneous Lift and Guidance
Authors: Limbert D. A. , Richardson H. H. , Wormley D. N.
Published: November 2010

Static and dynamic analytical models are derived for an attractive ferromagnetic vehicle suspension. The suspension consists of a pair of laterally offset electromagnets, reacting with an inverted U-shaped iron rail, which are controlled using the sum and difference of the magnet pair currents to achieve simultaneous lift and guidance. The control currents are generated from relative gap displacement and absolute vehicle velocity and acceleration signals through an algorithm which yields minimal heave-sway coupling. The analytical models have compared favorably with experimental data from a small scale heave-sway motion test facility. Parametric design studies conducted with the models and experimental data show that adequate guidance forces can be obtained from laterally offset magnets with only small increases in suspension weight and power compared with lift-only magnets.
A Dynamics Simulation for a High Speed Magnetically Levitated Guided Ground Vehicle
Authors: Cherchas D. B.
Published: November 2010

An analysis and digital computer program are developed to simulate vehicle and guideway dynamic response. The magnetic levitation is of the electrodynamic suspension type. The mathematical model includes effects of the following: vehicle and guideway flexible deformations, vehicle suspension and propulsion pod translation relative to the vehicle, multiple guideway spans and aerodynamic loading. The simulation is programmed in such a way that the number of sequential spans over which the vehicle travels can be increased without increasing the degrees of freedom in the simulation. Illustrative results of the simulation are presented.