bluuebunny/crossref_metadata_2025 huggingface dataset:
A Design Basis for Vortex-Type Fluid Amplifiers Operating in the Incompressible Flow Regime
Authors: Wormley D. N. , Richardson H. H.
Published: November 2010

A rational procedure is developed for the design of a class of vortex amplifiers which operate in the incompressible flow regime. The procedure is based upon analytical and experimental studies conducted to determine the effects of fluid properties and geometry on vortex amplifier behavior. These studies indicate that the nondimensional amplifier characteristic is essentially independent of the maximum flow Reynolds number, vortex chamber height, and supply port area if each of these parameters is within a specified broad range of values. The nondimensional characteristic was found to depend fundamentally upon the chamber exit to outer periphery radius ratio and the control port area to exit port area ratio. A systematic method is provided for progressing from a set of desired amplifier performance specifications, which include maximum control and supply port pressure and flow requirements, to a specification of each critical amplifier dimension. Three-point predictions of the transfer characteristics are obtained and the characteristics are checked to determine if multiple values of total flow exist at the cutoff value of control flow. The measured performance of a planar vortex amplifier designed with the aid of the procedure was found to agree closely with the desired performance specifications.
Compressible Laminar Wake of a Thin Flat Plate
Authors: El Assar R. J.
Published: November 2010

A finite difference solution is presented for the laminar, compressible wake behind a flat plate at zero angle of attack. The solution of the boundary layer equations is carried out in the von Mises coordinate plane. A coordinate transformation which maps the infinite region into a finite one is also introduced. The accuracy and range of validity of the asymptotic and preasymptotic theories of Goldstein and Tollmien for the incompressible wake are discussed. The effect of the Mach number and initial conditions on the evolution of the wake is investigated. The analysis is applicable outside a trailing edge region of O(LRc−3/4) and for a constant density-viscosity product and Prandtl number unity.
Similarities and Differences in the Erosion Behavior of Materials
Authors: Sheldon G. L.
Published: November 2010

A discussion is presented on the behavior of materials during erosion. A rigorous analysis must make an assumption as to the mechanism of material removal, i.e., either ductile or brittle. One expects then, when comparing experimental results, that considerable differences in erosion characteristics will be apparent between these two classes of materials. In this paper it is shown that these differences do exist; however, for certain brittle materials, a considerable similarity to ductile materials exists. This similarity is in the dependence of erosion on abrasive particle velocity and diameter and on the material properties of the eroded surface.
On the Thermodynamics of Nucleation in Weak Gas-Liquid Solutions
Authors: Ward C. A. , Balakrishnan A. , Hooper F. C.
Published: November 2010

Gas-vapor nucleation in liquid solutions is considered. It is shown that for nucleation to occur in a multicomponent solution a nucleus must be created of at least a certain radius. Consideration is then restricted to weak solutions of gas dissolved in liquids with the gas allowed to behave nonideally. A generalized Kelvin equation is derived which relates the partial pressure of the solvent vapor inside a nucleus to the properties of the surrounding solution. It is shown how, for a given temperature, the pressure at which nucleation occurs in a gas-liquid solution is increased as the gas concentration is increased.
Turbine Flowmeter Performance Model
Authors: Thompson R. E. , Grey J.
Published: November 2010

A theoretical model of a turbine meter operating in the high Reynolds number regime has been formulated to study the effects of retarding torques, inlet velocity profile, blade interference effects, meter geometry, and other factors. A computer program predicts actual rotor speed by numerical integration of the lift and drag forces on the rotor blade. Numerical sample calculations indicated substantial effects due to velocity profile and blade interference. Retarding torques were relatively unimportant in the high Reynolds number range.
Performance of Conical Diffusers With Annular Injection at Inlet
Authors: Nicoll W. B. , Ramaprian B. R.
Published: November 2010

Data on the gross performance of conical diffusers subjected to annular secondary injection at inlet are reported. Tests indicate that the improvement in diffuser performance is significant even at moderate rates of injection. The effects of injection rate and diffuser geometry on the pressure recovery and stall are discussed. An analytical method based on the solution of the boundary layer equations by the Patankar-Spalding finite difference method has been used to obtain predictions of pressure recovery with inlet injection. The predictions compare well with the experimental results.
The Response of a Turbulent Boundary Layer to an Upstanding Step Change in Surface Roughness
Authors: Antonia R. A. , Luxton R. E.
Published: November 2010

Measurements of the flow field downstream of an upstanding step change in surface roughness are presented. The roughness has the form of two-dimensional square section ribs placed transversely across the floor of the wind tunnel with the first element upstanding from the surface. The surface upstream of the roughness is smooth and is of sufficient length to allow a fully developed smooth wall turbulent boundary layer to be established. The roughness height is approximately 6 percent of the boundary layer thickness on the smooth wall just upstream of the first roughness element. It is observed that downstream of the start of the roughness, the mean velocity profiles inside the internal layer (i.e., that part of the boundary layer which has been affected by the new inner boundary condition) exhibit a linear trend when plotted in the form U versus y1/2. Remarkably, it is also found that a linear trend is exhibited by points in the “undisturbed” boundary layer outside the internal layer when plotted in the above manner, and that the slope in the undisturbed layer differs from that in the internal layer. The undisturbed layer slope appears to depend on conditions upstream of the roughness. It is suggested that the point of inter section of the two straight lines (the “knee” point) on the U versus y1/2 plot may be used to define the edge of the internal layer. Turbulence intensity distributions and spectra are presented from which it is deduced that the internal and external layer structures are largely independent and that stream-wise length scales in the internal layer over the rough wall are reduced significantly below those at the equivalent station over a smooth wall.
Generalized Expansion Factor of an Orifice for Subsonic and Supercritical Flows
Authors: Benedict R. P.
Published: November 2010

General expressions are developed which approximate the expansion factor of any orifice in any installation for both subsonic and supercritical flows. These factors are based on a presumed knowledge of the incompressible contraction coefficient for the same orifice. Comparisons are made between the suggested approximations and: ASME empirical expansion factors; previous experimental studies; and new experimental work.
Heat Transfer Characteristics in Air Fluidized Solids up to 900 F
Authors: Callahan J. T.
Published: November 2010

A theory for the mechanism of heat transfer in gas fluidized solids has been developed. Supporting data has been obtained. An empirical equation which fits the theory and correlates the data has been determined. Many sample calculations are given so that the equation can be used in design work.
Determination of Residual Stresses From Stress Intensity Factor Measurements
Authors: Vaidyanathan S. , Finnie I.
Published: November 2010

It is shown that a familiar procedure for obtaining stress intensity factors for a plate containing a through crack may be inverted. That is, stress intensity factor measurements may be used to deduce the state of stress that existed in the plate prior to introduction of the crack. This approach to residual stress measurement appears to be superior to existing methods for situations in which the stress gradients in the plane of the plate are large. As an illustration, the residual stress distribution in an electron beam welded aluminum plate is determined.
Thermal Effects in the Free Oscillation of Gas Bubbles
Authors: Chapman R. B. , Plesset M. S.
Published: November 2010

A theory is developed from first principles which includes all the important physical processes which affect the frequency of the free oscillations of a gas bubble. The components of the damping: viscosity, thermal conduction in the gas, and acoustic radiation are all determined. Numerical results for the damping are given for air bubbles in water. Since there is physical interest in the polytropic exponent, κ, (in pVκ = const.), the value of κ which gives the correct natural frequency is also determined. Numerical results for this κ for air bubbles in water are presented.
Error Bounds on Elastic-Plastic Strain Wave Measurements
Authors: Wagner J. G.
Published: November 2010

Bounds are established on the errors associated with elastic-plastic strain wave measurements involving finite gage lengths. Attention is restricted to the case of one-dimensional wave propagation in a semi-infinite bar. A bi-linear model of the stress-strain behavior provides a means of calculating realistic upper and lower bounds on the relative error of amplitude measurements. Rise time errors are also discussed and illustrated.
A Prediction of Water-Entry Cavity Shape
Authors: Abelson H. I.
Published: November 2010

A method is described for predicting the shape of the cavity formed when a projectile enters the water vertically from air, as a function of time. The method, developed by Birkhoff and based on a hydraulic flow model, has been shown to be applicable for entries of bluff, axisymmetric projectiles. A knowledge of the projectile weight, entry velocity, and cavity-running drag coefficient is required. Predicted and observed cavity shapes are compared for the entry of a sphere at very reduced pressure and the entry of a conical-nosed cylinder from normal air. Excellent agreement is observed over almost the entire cavity length.
Flow Investigation in a Francis Turbine
Authors: Fachbach H.
Published: November 2010

Results of both theoretical and experimental investigations of the flow in a Francis water turbine are presented. The flow visualization with the aid of rotating five-borehole probes provides the relative velocities, the pressure and energy distribution, the slip factor, the boundary layers, and the secondary flow. It is the intent of this paper to compare the theoretical and experimental results and to inform about the usefulness of the assumptions based upon the method of computation.
Numerical Method for Determining Stress Intensity Factors of an Interior Crack in a Finite Plate
Authors: Wilson W. K.
Published: November 2010

A boundary collocation method for estimating the stress intensity factors for a through-thickness interior crack in a plate of arbitrary geometry and arbitrary in-plane loading on the plate outer-boundary and crack surfaces is presented. The collocation is carried out on an Airy stress function which is derived from a previously given complex stress function. Various types of boundary collocation procedures are investigated. It is shown that collocation on the Airy stress function and its normal derivative gives the most accurate results. The method is applied to rectangular plates containing center cracks of arbitrary angular orientation. A number of plate edge and crack edge loading conditions are analyzed. The stress intensities calculated by this method compare very favorably with existing solutions for cases in which such solutions are available.
Phase Transformation Effects on the Bending Stress Distributions in Carburized Steel Components
Authors: McGuire M. F. , Troiano A. R. , Ebert L. J.
Published: November 2010

An analytical model has been developed for the elastic and elastoplastic bending of rectangular bars in which the neutral bending plane need not remain in the geometric center of the bar. With this model, distribution of both longitudinal and transverse stress can be computed on the basis of applied bending moment and measured, surface strains. The strain-induced transformation of austenite retained in the case of carburized steel bars of several compositions was found to occur at linear rates whose values depend upon the sign of the stress and the composition of the steel. It was further found to produce pronounced shifts in the neutral bending plane and to have major effects on the magnitude of the transverse bending stresses. The bending fracture characteristics of the carburized steel bars were found to be affected by the inherent toughness of the case, and all factors which influence it, as well as the inherent toughness of the core. In general, the presence of nickel in the steel enhanced the fracture resistance of the steels because of its contribution to the toughness of both case and core.
Nonlinear Effects in the Collapse of a Nearly Spherical Cavity in a Liquid
Authors: Chapman R. B. , Plesset M. S.
Published: November 2010

The collapse of pure vapor bubbles in an infinite liquid initially perturbed from a spherical shape is simulated numerically for two cases. In Case A the bubble is initially close to a prolate ellipsoid, and in Case B it is initially close to an oblate ellipsoid. Nonlinear effects are determined by comparing the results with those predicted by the linearized theory of Plesset and Mitchell. These nonlinear effects are found to be important only in the final stages of collapse. In Case A a pair of inward moving jets develop and strike each other with a final speed which is roughly half that, predicted from the linear theory.
Effects of Heat and Mass Transfer on Rayleigh-Taylor Instability
Authors: Hsieh D. Y.
Published: November 2010

The effect on the interfacial gravity wave between two fluids is studied when there is a temperature gradient in the fluids. It is found that the thermal effect is closely related to the phase transformation across the interface. The interfacial conditions with mass flow are first derived. Then the dispersion relation for the interfacial wave is obtained. It is found that the effect of evaporation is to damp the interfacial wave and to enhance the Rayleigh-Taylor instability. It is also found that the system will be stabilized or destabilized depending on whether the vapor is hotter or colder than the liquid.
On Flow Past a Supercavitating Cascade of Cambered Blades
Authors: Hsu C. C.
Published: November 2010

A linearized theory for supercavitating flow through a cascade of cambered blades is developed. Numerical results illustrating various points of interest are presented.
Spectrum Loading and Crack Growth
Authors: Wheeler O. E.
Published: November 2010

An analytical device for improving the accuracy of crack growth predictions in metal subjected to variable amplitude cyclic loading is presented. A modification to the linear cumulative growth idea is proposed which incorporates a consideration of prior load history by taking into account the yield zone ahead of the crack tip. Correlation between analysis and experimental results for six different cases shows that the scheme, even though only a first order improvement on the Miner idea, is sound and can be used with confidence for design and analysis.
Velocity and Shear Stress Distributions in a Transpired Turbulent Boundary Layer
Authors: Nayak U. S. L. , Barden R. G.
Published: November 2010

An attempt has been made in this paper to describe the velocity structure of a transpired turbulent boundary layer. The analysis makes use of a “wall-plus-wake” concept and derives a universal representation of the velocity structure of the turbulent boundary layer with uniform injection, “blow-off” or suction. The results of the analysis agree reasonably well with those obtained using an implicit finite difference technique advanced by Patankar and Spalding. The results also show a good correlation with the experimental data of Mickley, et al., and Simpson, et al. Predicted shear stress distributions compare well with the experimental data of Wooldridge, et al.
An Analysis of Axisymmetric Turbulent Flow Past a Long Cylinder
Authors: White F. M.
Published: November 2010

An analysis is presented which predicts the properties of an arbitrarily thick turbulent boundary layer for incompressible axial flow past a long cylinder. The approach makes use of a modified form of the law-of-the-wall, deduced by G. N. V. Rao, which properly accounts for transverse curvature effects. Using this law, the theory which follows is equivalent to an exact solution to the axisymmetric equations of continuity and momentum for zero pressure gradient. Numerical results show that curvature increases skin friction and overall drag and decreases the boundary layer thickness and the integral thicknesses. The velocity profile is flattened and the shape factor approaches unity at large curvature. Comparison with several sources of friction data show better overall agreement than previous theories, except for an unexplained discrepancy with data for moving nylon fibers at very small radius Reynolds numbers.
Conical Flows in Metal Forming
Authors: Ahmed N.
Published: November 2010

An improved velocity field based on the solution to an incompressible fluid flow is used to establish an upper bound approach for conical flows in metal forming. From a three parameter characterization of the equivalent stress-equivalent strain data on copper and aluminum, the effects of work hardening on forming stresses, maximum reduction ratios, optimum cone angles, and dead zone angles are studied for drawing, conventional, and hydrostatic extrusion. Results for a rigid-plastic material are obtained as a special case of the work hardening material. Experimental data are offered to show an excellent correlation with theory. A representation for the redundant work factor is developed that incorporates in it the effects of material properties and flow geometry. The existence of maximum pressure well inside the plastic region is pointed out and the possibility of introducing the forming fluid at some distance inside the die to facilitate better lubrication is examined.
Energy Spectrum and Turbulent Scales in a Circular Water Jet
Authors: Goldschmidt V. W. , Chuang S. C.
Published: November 2010

The time micro and macroscales are computed from measured energy spectra in the fully developed region of a submerged circular water jet. The corresponding longitudinal scales are approximated using Taylor’s frozen turbulence hypothesis. The microscale is found essentially constant whereas the macroscale, although increasing linearly along the axis, does not show similarity in the total field.
Anisotropy in Plastic Torsion
Authors: Bailey J. A. , Haas S. L. , Nawab K. C.
Published: November 2010

An analysis is presented which shows how the theory of anisotropy based on a von Mises criterion of yielding first proposed by Hill may be extended to the plastic torsional straining of a hollow cylinder. Expressions are given for the anisotropic parameters, and the yield stresses along the anisotropic axes in terms of certain quantities, namely; the change in axial and tangential strain with shear strain, the principal yield shear stress, and the through thickness yield stress of the hollow cylinder. Experimental measurement of these quantities is made for the plastic torsional straining of hollow cylinders of A1-1100. Experimental data are analyzed using the previously derived expressions, and the anisotropic parameters, and yield stresses along the anisotropic axes determined. Finally, the results of the investigation are discussed, and conclusions drawn.
Applications of a General Method of Calculating Turbulent Shear Layers
Authors: Bradshaw P. , Ferriss D. H.
Published: November 2010

A calculation method using a differential equation for the turbulent shear stress has been successfully applied to boundary layers with compressibility, heat transfer, three-dimensionality or unsteady flow, with an empirical input obtained almost entirely from low-speed flow at constant pressure. With numerical changes in the empirical input the method has been extended to duct flows and free shear layers. Running times are typically 5–10 sec on a CDC 6600 or five times this on an IBM 7094; programs are freely available from the authors.
Numerical Error on Natural Gas Transient Calculations
Authors: Yow W.
Published: November 2010

In this paper a new concept of the inertial multiplier is introduced to relax the restriction of the time increment in a computation method for natural gas transient analysis. The range of usefulness of this multiplier and the criteria on the allowable reach length for natural gas transient flow calculation are presented. The validity and the application of the criteria are demonstrated by practical examples. A semianalytical solution with the second-order approximation to the nonlinear difference equations for steady oscillatory flow in natural gas systems is also discussed.
The Transient Response of Orifices and Very Short Lines
Authors: Funk J. E. , Wood D. J. , Chao S. P.
Published: November 2010

It is generally assumed that orifices and valves follow closely their steady-state characteristics during transient operation. However, this assumption of quasisteady behavior may lead to errors in predicting transient flow conditions under certain circumstances. In order to evaluate the transient behavior of an orifice, a differential equation relating the flow through and the pressure drop across an orifice was derived. An extension was made to include an axial dimension for the orifice. The solution of this equation for transient flow through an orifice subjected to a step change in pressure drop across the orifice is significantly different than that obtained using the steady state relationship. An experiment was designed to evaluate the theoretical results in which an orifice on the end of a line was subjected to a sudden pressure change and the resulting transient pressures were observed. It was found that a significant short term transient occurs before the orifice flow reaches the new steady state condition. The observed short term transient agrees well with that predicted by the theory. It is concluded that the behavior of an orifice can deviate considerably from that predicted by steady-state equations during periods of rapid pressure or flow changes. The dynamic description of orifice flow may be combined with a larger system analysis (e.g., using the method of characteristics) to more accurately predict the overall transient performance of flow systems.
Study of Flow Phenomena in the Impeller Passage by Using a Singularity Method
Authors: Reddy Y. R. , Kar S.
Published: November 2010

The vortex, the velocity, and the pressure distribution along the vane surfaces are calculated for two impellers, one having six vanes and the other twelve vanes. The vanes were of logarithmic shape with a blade angle of 30 deg and impeller inlet to exit radius (r1/r2) ratio of 0.6. All the foregoing quantities were calculated for five different flow coefficients from 0.05 to 0.25 in steps of 0.05 for both the impellers. In the case of impellers with twelve vanes, the flow phenomena were also calculated at a flow coefficient of 0.16 so as to compare with the published results.
Some Observations Relating to Suction Performance of Inducers and Pumps
Authors: Yedidiah S.
Published: November 2010

Tests performed with a remarkable number of inducers and pumps indicate that there exists a definite pattern of the manner in which the velocity of flow of the liquid and the peripheral velocity of the inlet tips affect the suction characteristics of a pump. Within certain limits, this pattern is unaffected by the shape of the blades, by the type of the pump, and by the flow rate. This consistency of behavior allows one to calculate the NPSH-requirements of a pump along its total working range, provided that the suction conditions are not disturbed by a particularly unfavorable blade geometry or by other effects.
An Investigation of Confined Vortex Flow Phenomena
Authors: Kwok Clyde C. K. , Thinh Ngo Dinh , Lin Sui
Published: November 2010

The swirling, incompressible flow within a short vortex chamber of aspect ratio 1/9, defined by the ratio of chamber height to chamber diameter, has been investigated analytically. The theoretical analysis consists of the adaptation of Wormley’s analytical technique and the extension of the method to include the apparent viscosity factor. The Runge-Kutta method is used to solve numerically the set of differential equations. The analytical results are compared with those of the experimental investigations conducted by Savino and Keshock. The analytical results prove that the values of apparent viscosity seriously affect the velocity profiles within the vortex chamber. The results also show that the apparent viscosity varies from 7000μ at the vortex chamber periphery to 4500μ at the orifice exit plane, where μ is the operating fluid viscosity. An empirical expression for the apparent viscosity is found in the form μa = K1νδn + K2, where n, K1, and K2 are constants and νδ is the tangential velocity. The constants n, K1, and K2 are found to be −1/3, 0.01, and 0.0005, respectively, for this investigation.
Natural Breakdown of Planar Jets
Authors: Rockwell D. O. , Niccolls W. O.
Published: November 2010

The growth of planar jets is studied using the hydrogen bubble technique of flow visualization. A five-fold range of nozzle exit Reynolds number (1860 to 10,800) is considered. Generation of streaklines and timelines permits characterization of the process of vortex formation and coalescence. Both symmetrical and asymmetrical modes of vortex growth and coalescence, along with the resultant deformation of the jet core flow, are examined. Nascent and mature stage coalescence are defined and portrayed. Vortex axial transport velocity and frequency of formation of the vortices are evaluated for selected Reynolds numbers.
The Swirling Turbulent Jet
Authors: Pratte B. D. , Keffer J. F.
Published: November 2010

An experimental investigation has been made of a swirling jet having a moderate ratio of swirling to axial momentum. Measurements showed that the flow achieved a self-similarity for the mean velocities rather quickly while the normal turbulent intensities reached a self-similar state after a longer period of jet development. Conservation arguments were used to predict streamwise decay rates for the mean quantities. The analysis showed that the maximum axial and swirling velocity components should vary asymptotically as (x − x0)−1 and (x − x0)−2, respectively. The experimental results confirmed this satisfactorily. The minimum static pressure was predicted to vary at a rate proportional to (x − x0)−4. Measurements indicated, however, that the relation was closer to (x − x0)−2. Better agreement with the data was achieved when the analytical expression was adjusted for the effect of the turbulence terms. The entrainment rate and angle of spread for the swirling jet were found to be nearly twice that of the non-swirling free jet.
Visualization Study of Flow in Axial Flow Inducer
Authors: Lakshminarayana B.
Published: November 2010

A visualization study of the flow through a three ft dia model of a four bladed inducer, which is operated in air at a flow coefficient of 0.065, is reported in this paper. The flow near the blade surfaces, inside the rotating passages, downstream and upstream of the inducer is visualized by means of smoke, tufts, ammonia filament, and lampblack techniques. Flow is found to be highly three dimensional, with appreciable radial velocity throughout the entire passage. The secondary flows observed near the hub and annulus walls agree with qualitative predictions obtained from the inviscid secondary flow theory. Based on these investigations, methods of modeling the flow are discussed.
Horizontal Forces Due to Waves Acting on Large Vertical Cylinders in Deep Water
Authors: Johnson E. R.
Published: November 2010

The special case of horizontal wave forces on large vertical cylinders in deep water is considered. The typical application for such a case is the calculation of horizontal forces on column stabilized floating ocean platforms. Existing literature discussing horizontal wave forces on cylinders does not generally agree on how to predict these forces. Since for large diameter cylinders in deep water the maximum force is completely inertial, the problem of deriving a solution is considerably simplified. In this study, an expression for the maximum horizontal wave force on large diameter circular cylinders mounted vertically in deep water has been analytically derived. Experimental model studies were also conducted and the resulting measured forces were within 20 percent of predicted forces. An example of how to predict horizontal wave forces using the methods of this report is given.
Rheological Response of Human Brain Tissue in Shear
Authors: Shuck L. Z. , Advani S. H.
Published: November 2010

Head injury is often attributed to transient shear stresses arising from rotation of the brain in the cranial cavity. This paper deals with the experimental determination and analytical characterization of in vitro human brain dynamic constitutive properties in pure shear. A closed loop, feedback torsional system with a self mass cancelling torque transducer is used for the experimental study. Values of the storage and loss components of the dynamic shear modulus are computed and a four parameter, linear, visco-elastic model representing brain tissue properties up to 350 Hz is presented. In addition, failure criterion in terms of limiting strains and strain rates are identified.
The Influence of the Cavitation Nucleus Spectrum on Cavitation Inception, Investigated With a Scattered Light Counting Method
Authors: Keller A.
Published: November 2010

For model tests on cavitation inception, the knowledge of the size distribution and frequency of occurrence of free nuclei is important. For this reason, an optical measuring method was developed for determining the bubble nuclei spectrum. In conjunction with measuring the bubble nuclei spectrum, a set of tests on cavitation inception was carried through, with each test leading basically to the same conclusions: The number and size of the bubble nuclei in water are dependent on the history of the particular water and on its content of contamination particles; the cavitation inception at a submerged body is strongly affected by the bubble nuclei content.
The Application of Rotating Flow Theory to the Flow Inside a Break Spinning Apparatus
Authors: Bluston H. S. , Paulson R. W.
Published: November 2010

The “break spinning” process has recently been introduced to improve spinning efficiency in the textile industry. In one version, fiber elements are drawn onto the inner rim of a rapidly rotating drum from which they are pulled away, as yarn, by means of a thread inserted along the axis. The quality of the yarn produced is considered to be sensitive to the air flow in the drum. The object of this work is to apply simple rotating flow theory, to obtain the angular velocity distribution inside the drum.
A Theoretical Analysis of CO2 Absorption in Sun Versus Shade Leaves
Authors: Rand R. H.
Published: November 2010

A one-dimensional, steady-state, constant temperature model of diffusion and absorption of CO2 in the intercellular air spaces of a leaf is presented. The model includes two geometrically distinct regions of the leaf interior, corresponding to palisade and spongy mesophyll tissue, respectively. Sun, shade, and intermediate light leaves are modeled by varying the thicknesses of these two regions. Values of the geometric model parameters are obtained by comparing geometric properties of the model with experimental data of other investigators found from dissection of real leaves. The model provides a quantitative estimate of the extent to which the concentration of gaseous CO2 varies locally within the leaf interior.
Determining Muscle Forces in the Leg During Normal Human Walking—An Application and Evaluation of Optimization Methods
Authors: Hardt D. E.
Published: November 2010

The individual muscle forces in the leg during human walking are unknown, because of a greater number of muscles when compared to degrees of freedom at the joints. The muscle force-joint torque equations can be solved, however, using optimization techniques. A linear programming solution of these equations applied at discrete, time-independent steps in the walking cycle using dynamic joint torque data is presented. The use of this technique, although capable of providing unique solutions, gives questionable muscle force histories when compared to electromyographic data. The reasons for the lack of confidence in the solution are found in the inherent limitations imposed by the linear programming algorithm and in the simplistic treatment of the muscles as tensile force sources rather than complex mechanochemical transducers. The definition of a physiologically rationalized optimal criterion requires both a global optimization approach and more complete modelling of the system.
Noninvasive Inference of Airway Network Geometry From Broadband Lung Reflection Data
Authors: Sidell R. S. , Fredberg J. J.
Published: November 2010

An inference of the summed cross-sectional area of the airway network of the lung as a function of distance from the airway opening can be obtained noninvasively by inversion of high-frequency reflection response data with the Ware-Aki algorithm. This method is critically evaluated. The response of branching models of the complete tracheo-bronchial tree are simulated and inverted to produce an area versus distance inference. The models incorporate branching asymmetry, nonrigid walls, and a viscous gas. Direct comparison of the area inference with the anatomic area of the model indicates that the inference is markedly influenced by nonrigidity of the airway walls and branching asymmetry, and that the inference does not possess a simple anatomic correlate. Empirical uses of the inference method are not precluded.
Measurement of Burn-Induced Leakage of Macromolecules in Living Tissue
Authors: Green D. M. , Diller K. R.
Published: November 2010

An experimental technique has been developed to measure changes in vascular permeability caused by thermal trauma to the microvascular bed of the hamster cheek pouch. A solution of flourescein isothiocyanate (FITC) conjugated dextran was injected directly into the circulatory system. Subsequent leakage of dye from vessels into the extravascular space was directly observed by light microscopy and recorded by sequential photography. Individual frames of the filmed record of the trauma and post-trauma process were digitized and analyzed by computer. A point-by-point densitometric evaluation of the digitized image provides a measure of extravascular accumulation of dye-tagged dextran. Preliminary results indicate that preburn treatment with large doses of heparin yields a significant reduction in burn-induced edema.
Air Mixing in a Model Lung Alveolus
Authors: Yu C. P. , Rajaram S. , Taulbee D. B.
Published: November 2010

The quasi-steady creeping flow in a spherical model alveolus has been studied by solving the Stokes equations numerically in order to understand the airflow in the alveolar region of the human lung. The alveolar shape is allowed to change during the respiratory cycle such that the alevolar mouth opening as a fraction of the surface is a function of the lung volume. The complete velocity field in the alveolus is determined from which a hypothetical interface between the tidal and residential airs before and after a respiratory cycle is calculated. The result shows that there is significant mechanical mixing between the two airs and the calculated percentages of mixing in the lung agree favorably with the existing data from single breath measurement using half-micron aerosols.
Vortex Motion and Induced Pressures in a Model of the Aortic Valve
Authors: Swanson W. M. , Ou S. A. , Clark R. E.
Published: November 2010

A self-propagating, free-vortex pair is mapped into an infinite strip, and a semi-infinite strip. The strip geometries are plane two-dimensional approximations of the open and closed aortic valve regions. Vortex trajectories, velocity fields and pressure distributions are calculated. The unsteady vortex motion is shown to initiate valve closure during systolic flow deceleration. These closure initiation effects are compared to and combined with flow field and pressure gradient effects considered by other investigators.
Mechanical Properties of Human Lumbar Spine Motion Segments—Part I: Responses in Flexion, Extension, Lateral Bending, and Torsion
Authors: Schultz A. B. , Warwick D. N. , Berkson M. H. , Nachemson A. L.
Published: November 2010

In this first part of a three-part report, the mechanical behavior of 42 fresh human cadaver lumbar motion segments in flexion, extension, lateral bending, and torsion is examined. Motions and intradiskal pressure changes that occurred in response to these loads, with posterior elements both intact and excised, are reported.
A Dynamic, Nonlinear Finite-Element Model of a Human Leg
Authors: Hight T. K. , Piziali R. L. , Nagel D. A.
Published: November 2010

The development of a dynamic, nonlinear finite-element model of a human leg is presented. The model is designed to accommodate large three-dimensional displacements and rotations, to accurately reflect the nonlinear stiffness characteristics of the knee joint, and to facilitate efficient stress-level calculations. Numerical examples are presented which demonstrate the nonlinear capabilities of the model. In addition, a brief example illustrates the ability of the model to respond to a complex loading history measured during a downhill skiing maneuver and to predict cross-sectional stress levels.
A Proposed Model of Boundary Lubrication by Synovial Fluid: Structuring of Boundary Water
Authors: Davis W. H. , Lee S. L. , Sokoloff L.
Published: November 2010

On the basis of data obtained from in-vitro friction tests using both cartilage and widely differing artificial surfaces, a general model for boundary lubrication of joint cartilage by synovial fluid is presented. It postulates that one portion of the synovial lubricating glycoprotein (LGP) is adsorbed to the surface. Reduction in surface shear is accomplished by formation of hydration shells about the polar portions of the adsorbed LGP creating a thin layer of viscous structured water at the surface. Mutual electrostatic repulsion between charged polysaccharide moieties aids in separation of the adsorbed surface layers. The hydration shell also serves as a check valve to control the movement of water out of and into the cartilage matrix during motion.
Numerical Study of the Steady Axisymmetric Flow Through a Disk-Type Prosthetic Heart Valve in an Aortic-Shaped Chamber
Authors: Underwood F. N. , Mueller T. J.
Published: November 2010

Numerical solutions for the steady axisymmetric flow through a disk-type prosthetic heart valve were obtained for Reynolds numbers from 50 to 600. A nonuniform mesh in both directions was used and the finite difference equations in vorticity and stream function were solved explicitly. Stream function, vorticity, and shear and normal stress plots are presented. These detailed results clearly identify regions of very high shear and normal stresses, regions of very low or very high shear stress at the walls and the extent of separated or reverse flow regions. The length of the separated flow region downstream of the disk agreed very well with experimental data. The maximum value of the shear stress occurred on the upstream corner of the disk.
Contractile Filament Stress in the Left Ventricle and its Relationship to Wall Stress
Authors: Grood E. S. , Phillips C. A. , Mates R. E.
Published: November 2010

A three-dimensional composite model of heart muscle is proposed, consisting of one-dimensional (uniaxial) active contractile filaments embedded in a passive elastic binder. Equations are developed which relate the force developed by the filaments to the local tissue stress. An approximate analysis is employed to determine the time variation of the contractile filament stress throughout the cardiac cycle from catheterization data. Results from 15 patients with normal left ventricles demonstrate that the stress developed by the contractile filaments is up to 25 percent more tensile than the wall stress, and that the binder stress is compressive during most of systole. In contrast, the one-dimensional lumped parameter muscle models previously employed predict active (CE) stresses less tensile than the wall stress and binder (PE) stresses that are tensile. We conclude that the use of a one-dimensional muscle model results in a significant underestimation of the active force generation required for pressure development and the power requirements for ejection. Prior studies relating muscle work and power to ventricular oxygen consumption should be re-examined in this light.
Prediction of Bending Strength of Long Bones From Measurements of Bending Stiffness and Bone Mineral Content
Authors: Borders S. , Petersen K. R. , Orne D.
Published: November 2010

The relationship between fracture strength in bending, bending stiffness and bone mineral content for 56 fresh canine radii, ulnae and tibiae was determined from three- and four-point bending tests on a MTS testing machine and from measurements of bone mineral content at the fracture site using the Norland-Cameron Bone Mineral Analyzer. The high correlation of bending stiffness (0.962) and mineral content (0.901) with fracture bending moment permits estimates of fracture strength using current noninvasive methods of measuring stiffness and mineral content.
The Concentration Polarization Effect in Frozen Erythrocytes
Authors: Levin R. L. , Cravalho E. G. , Huggins C. E.
Published: November 2010

An ideal, hydrated, nondilute pseudo-binary solution model is presented to describe the concentration polarization of solutes within cells during osmotic experiments. This model has been applied to the case of hyman erythrocytes being cooled at subzero temperatures. The concentration polarization of solutes within the RBC intracellular solution during freezing reveals the fact that the water transport process is significantly affected not only by the permeation of water through the cell membrane, but also by the diffusion of water within the intracellular medium.
Numerical Study of the Steady Axisymmetric Flow Through a Disk-Type Prosthetic Heart Valve in a Constant Diameter Chamber
Authors: Underwood F. N. , Mueller T. J.
Published: November 2010

Numerical solutions for the steady axisymmetric flow through a disk-type prosthetic heart valve were obtained for Reynolds numbers from 20 to 1300. Stream function, vorticity, and shear and normal stress plots are presented. Comparison of the length of the separated flow region downstream of the disk with experimental data shows good agreement through Reynolds number 500. The maximum value of the shear stress occurred on the upstream corner of the disk. These detailed results clearly identify regions of very high shear and normal stresses (erythrocyte deformation or damage), regions of very low or very high shear stress at walls (atheromatous lesions), and the extent of separated or reverse flow regions (thrombosis).
Application of The Parameter Plane Method to The Analysis of Directional Stability of Tractor-Semitrailers
Authors: Guntur R. R. , Wong J. Y.
Published: November 2010

This paper describes the application of the parameter plane method to the study of the effects of design and operational parameters on the directional stability of tractor-semitrailers. The location of the fifth wheel, loading conditions of the semitrailer, and cornering stiffnesses of tires are taken as parameters in the analysis. Stability boundaries for two tractor-semitrailer combinations with different brake systems are drawn on parameter planes as illustrative examples to demonstrate the utility of the method. In the analysis, the effects of normal load and braking effort on the stiffness of tires have been taken into consideration. It is shown that the parameter plane technique can provide the designer with a convenient method to evaluate the relative significance of various design and operational parameters to directional stability.
Stability Tests for One, Two, and Multidimensional Linear Systems
Authors: Jury E. I.
Published: November 2010

This paper reviews analytical stability tests for one-dimensional linear systems since the early tests of E. J. Routh in his famous Adams Prize essay of 1877. The historical background of Routh’s stability test and criterion, as well as Fuller’s conjecture on its simplification, will be mentioned. In this historical review, the works of Hermite, Sylvester, Maxwell and others as related to the stability problem are also discussed. This review provides the context for a discussion of recent stability tests obtained for two-dimensional and multidimensional linear systems. These tests are described and their computational complexity is discussed in detail. In addition, the applications of stability testing to the study of two- and multidimensional digital filters, numerical analysis of stiff-differential equations, realization of mixed lumped and distributed parameter systems, and the design of output feedback systems will be briefly mentioned. Comments on future research in this area concludes the paper.
A Technique for Compensating the Filter Performance by a Fictitious Noise
Authors: Yoshimura Toshio , Soeda Takashi
Published: November 2010

This technical brief is concerned with an adaptive technique for compensating the filter performance in an erroneous system model. The degradation of the performance is covered by adding a fictitious input noise and adaptively estimating the statistics. The estimates of the statistics are evaluated by exponentially ageing the old information about them. Numerical results show that the proposed approach is much more improved than a suboptimal filter.
Carathe´odory Controllability Criterion for Nonlinear Dynamical Systems
Authors: Langholz G. , Sokolov M.
Published: November 2010

The question of whether a system is controllable or not is of prime importance in modern control theory and has been actively researched in recent years. While it is a solved problem for linear systems, it is still an open question when dealing with bilinear and nonlinear systems. In this paper, a controllability criterion is established based on a theorem by Carathe´odory. By associating a given dynamical system with a certain Pfaffian equation, it is argued that the system is controllable (uncontrollable) if its associated Pfaffian form is nonintegrable (integrable).
Optimization of Rail Vehicle Operating Speed With Practical Constraints
Authors: Cox J. J. , Hedrick J. K. , Cooperrider N. K.
Published: November 2010

A constrained optimization algorithm to maximize the operating speed of a fifteen degree-of-freedom lateral dynamic model for a passenger railcar subject to random alignment irregularities is presented in this paper. The constraints placed on the optimization problem limit the passenger discomfort, primary and secondary suspension clearance, the wheel slippage, and secondary suspension stroke to practical values while traversing a curve. The optimization results demonstrate that the primary suspension system and the wheel conicity have the most profound influence on maximizing the critical speed where “hunting” begins. The maximum critical speed is insensitive to large variations in secondary yaw stiffness. The secondary lateral stiffness has less effect on the maximum critical speed than the primary lateral stiffness. Thus, the secondary stiffness can be chosen primarily to satisfy passenger ride comfort specifications. The maximum critical speed is quite sensitive to whether the wheel is new, slightly worn, or severely worn.