bluuebunny/crossref_metadata_2025 huggingface dataset:
The Unsteady Flow and Wake Near an Oscillating Cylinder
Authors: Toebes G. H.
Published: November 2011

This paper reports on velocity, pressure, and correlation measurements in the turbulent wake and the adjacent unsteady potential flow of a circular cylinder. Particular attention is given to the effects that attend oscillation of the cylinder in the plane of the lift force. The study was undertaken for four reasons. First was the need to generalize measurement results on the lift force of an oscillating cylinder placed in a flow [1]. Second was the desire to clarify the fluidelastic nature of such forces. Third was the wish to compare gross features of real and computer generated flows. And fourth was the presumed possibility to create unsteady flow of controlled characteristics by using vibrating cylinders. The data presented here pertain to the velocity field close to the cylinder. Actually the records for locations further downstream suggest that prospects for control of flow characteristics using vibrating bluff cylinders do not look promising beyond, say, 15 dia. Measurements made close to the cylinder permit more definite conclusions. The fluidelastic nature of the flow associated with vortex-induced vibrations of cylinders has been demonstrated conclusively. Various existing notions about this question can now be segregated. Reynolds numbers of up to 105 were attained; this is sufficiently high to give results in the range of practical application. Revealing records about the flow field structure were acquired. They permit many conclusions by mere visual inspection because of the special attention given to the unsteady or potential flow region.
The Cause of White Etching Material Outlining Shell-Type Cracks in Rail-Heads
Authors: Henry R. J.
Published: November 2011

The cause of the white-etching regions outlining certain subsurface cracks in rail-heads was investigated. These cracks known as shells may propagate into “shelly spots,” i.e., deep spalls, usually in the gage corner in rail-heads. Samples containing these regions were metallographically compared to samples with scribed scratches. The white etching regions were found to be stress-induced microstructural changes resulting from the rolling contact fatigue in rail heads.
A Green’s Function for the Stress-Intensity Factors of Edge Cracks and Its Application to Thermal Stresses
Authors: Emery A. F. , Walker G. E. , Williams J. A.
Published: November 2011

A Green’s function for the computation of stress-intensity factors for edge cracks in rectangular plates is given for any distribution of stress in the uncracked plate which is tensile over the crack length. The function is used to compute stress intensity factors for transient thermal stresses produced by sudden cooling of one edge. Experimentally measured stresses and stress-intensity factors are given and shown to be in good agreement with the predicted values.
Dynamic Strain Aging and the Charpy Specimen Behavior of Annealed 4340 Steel
Authors: Clough W. R. , Jackman L. A. , Andreev Y. G.
Published: November 2011

V-notch Charpy bars were ruptured at seven deflection rates at test temperatures from the ambient through the blue-brittle range, while unnotched tensile specimens were equivalently tested at four strain rates. Objectives were to interpret and relate dynamic strain aging manifestations of annealed 4340 shown by the two types of tests. Comparisons are made with elastic-plastic formulations and experimental results for initial yielding and fracture of notched bars at or near room temperature. Quasi-cleavage fracture was observed in excess of 500 deg F. Dynamic strain aging effects are compared with those found with less alloyed lower carbon steels. Arrhenius type relations are developed and discussed, and from these other interrelations are derived, and mechanisms are discussed.
On the Optimal-Control Problem for Dynamical Processes With Variable Delays
Authors: Sebesta H. R. , Clark L. G.
Published: November 2011

The principles of calculus of variations are used to obtain necessary conditions for optimal control of dynamical systems that involve nonconstant time lags. Consideration is given to systems that can be represented mathematically by a finite set of ordinary nonlinear differential-difference equations with one or more time-dependent argument lags. Application of the general results to classes of linear systems with finite-time quadratic performance criteria is considered in detail. Optimal feedback control laws are given. Discussion of a proposed method for obtaining computational solutions for nonlinear systems with variable delays is included in the paper.
Aspects of Adaptive Optimal Steady-State Control
Authors: Pearson A. E.
Published: November 2011

The paper extends and modifies an approach to adaptive optimal control problems proposed by Kulikowski. The emphasis at the outset is placed upon optimizing the steady-state system performance in which the desired output of the plant is a periodic function of time. The formulation for type-one plants is modified to include the optimization of the total amount of input accumulation, s=∫−∞t0u(τ)dτ, which is present at the beginning of each period of steady-state operation.
Elastic-Plastic Stress Distribution in a Compressed Ring
Authors: Chang K. T. , Leopold P. M.
Published: November 2011

This investigation was conducted to define the plastic stress distribution at a section 90 degrees from the point of load application on a ring. The elastic and plastic stress distribution was determined experimentally by using postyield strain gages and the stress-strain relationship obtained from a uniaxial tensile test. The experimental results in the elastic range were found to agree with presently available theoretical predictions. A theoretical plasticity analysis of the ring was made by assuming that it deforms to the shape of an ellipse and that plane sections remain plane. The strains determined in this manner were used to calculate stresses off the tensile stress-strain curve. The experimental results indicated that this initial analysis gave a good approximation of the stress distribution for large deflections of the ring.
On the Behavior of Notched Struts
Authors: Cotterell B.
Published: November 2011

A theoretical buckling load for a strut with a single-edge notch at its mid point is calculated assuming that the effect of the notch is to produce a discontinuity in the slope of the strut. This buckling load is not likely to be reached if the material of the strut is at all brittle and it is shown that the fracture load can be calculated from the critical stress intensity factor of the material. Some justification to the theoretical treatment is obtained from the analysis of previous experimental results.
Structural Growth Induced by Thermal Cycling
Authors: Burgreen D.
Published: November 2011

A study is made of the ratcheting growth of an elastic-plastic one-dimensional element subjected to thermal cycling in the presence of a sustained axial load. The cyclic temperature distribution across the element is taken as either linear or parabolic. The cyclic growth of the element is computed as a function of the cyclic temperature and sustained axial load.
Two and Three-Dimensional Fluid Transients
Authors: Streeter V. L. , Wylie E. B.
Published: November 2011

The paper presents an approach for the analysis of low-velocity two and three-dimensional transient fluid-flow problems. The method assumes the continuum can be represented by a latticework of piping elements and that motion in the continuum can be described by solving the one-dimensional transient flow equations in the piping elements. The approach offers the advantage of being able to handle unusual and irregular boundary conditions, fixed or moveable, but restricted to the limitation of low Mach number. Undesirable grid characteristics are identified and comparisons with known hydrodynamic solutions are presented.
An Investigation of Pulsations in the Boiler Feed System of a Central Power Station
Authors: Dussourd J. L.
Published: November 2011

A field investigation was made to determine the source and character of pressure pulsations in the boiler feed system of a central power station. By systematic equipment elimination, it was concluded that the oscillation are caused by rotating stall in the boiler feed pump as it enters into resonance with the piping circuit. An analysis is carried out of the equivalent linear system under harmonic conditions. The analytical model provides reasonable agreement with the observations for the three tested piping configurations. Some insight is provided in the mechanism of the pulsations and the dynamic impedances of typical component equipment.
Dynamic Study of Temperature Transducers by Use of an Optical Method
Authors: Wagner R. E.
Published: November 2011

The dynamic study of thermal processes is often restricted by the limitations of the temperature transducers. The thermocouple is one of the most employed transducers because of its small size, but it presents several problems such as: (a) The delivered output is very small and for precision measurements problems appear concerning signal to noise ratios, and (b) the transient response is often not well known and is also sometimes insufficient. For this reason thermocouples have been studied by varying the different parameters. To be able to get a reference, permitting accurate measurements of a temperature variation as a function of time, an optical method has been constructed called the “Schlieren” method which allows visualization of a temperature variation and thereby renders feasible the recording of these variations without any appreciable time delay. The thermocouple itself is installed in the water-channel in which the temperature variations are recorded by the foregoing principles. The comparison of the two recordings defines the time constant of the thermocouple. For these measurements a special device has been constructed permitting the temperature to vary without any influence upon the other parameters (flow, pressure, and so on). The experiments have been made for different flow rates. Using the experimental values, an electric model for the thermocouple’s behavior has been devised by which the equivalent thermal resistors and capacitors could be determined. Thus the time constants of the thermocouples corresponding to other parameter values can be calculated. Similar tests to determine time constants have been made for thermal resistors, hot wires, and hot films. All tests described have been made by measuring water temperatures, but the results could easily be applied to other media.
Design of Nonlinear Sampled-Data System for Acceleration Measurement
Authors: Kasparian M. , Shen C. N.
Published: November 2011

The design of a sampled-data nonlinear system for three-axes acceleration measurement is discussed. The basic specific force equation is given, and the equation for the indicated velocity (integral of indicated acceleration) is derived to show the dependence of the error on the shape of the limit cycle trajectory. Emphasis is on how certain physical parameters, such as damping and dead zone width, may be chosen to fulfill the design requirement of minimum error in the indicated velocity output of the system. Expressions for design purposes relating physical parameters, such as damping, and phase plane switch line spacing to limit cycle period are derived. High limit cycle frequencies, or low periods, are shown to be less objectionable. An expression is given for the approximate dead zone width for minimum error from dynamic average and static offsets of the limit cycle trajectories. A multiscale-normalized phase plane technique is described and used to determine both the transient and final limit cycle trajectories for assumed step acceleration inputs at arbitrary points during an existing limit cycle.
Propagation of Disturbance in Fluid Lines
Authors: Ansari J. S. , Oldenburger R.
Published: November 2011

The purpose of this paper is to investigate the phenomena of the decay and dispersion of a disturbance pulse as it travels in a fluid along a pipe. A disturbance has associated with it deviations in the mean velocity and pressure. The disturbance pulse, therefore, may be considered as a velocity or a pressure pulse. By decay we mean here a decrease in the intensity, and by dispersion an increase in the width of the pulse with time. In an ideal nonviscous fluid contained in a rigid pipe, decay and dispersion do not occur, but are observed in the viscous fluids. A reflection of the pulse from a closed free end of the pipe also causes decay and dispersion. It is observed that for sufficiently low values of the coefficient of friction the viscous effects may be approximated by a pure decay without dispersion.
On the Generalized Bath-Tub Vortex
Authors: Harada M.
Published: November 2011

The general theory of the bath-tub vortex is reviewed, including both the effects of the secondary flow and the existence of an initial angular velocity. The effect of the secondary flow is demonstrated experimentally by measuring the flow angles at the air intake using a baffle plate set parallel and perpendicular to the Earth axis. The experimental proof was obtained by measuring the fluid vorticity through observation of the behavior of a cross shaped float.
Effect of Cavitation on the Discharge Coefficient of Standard Flow Nozzles
Authors: Kobayashi R.
Published: November 2011

Experiments were undertaken to determine the effect of cavitation on various standard flow nozzles. The results show that the discharge coefficient of the ASME long-radius flow nozzle remains unchanged even with violent occurrence of cavitation. This is also true for the ISA flow nozzle within the prescribed tolerance so long as cavitation number does not fall below a certain limiting value. Further experiments provide information on the locations of cavitation, on incipient pressures, and on its effect on the overall pressure loss through the flow nozzles.
Transonic Flow in Curved Channels
Authors: Thompson P. A.
Published: November 2011

Transonic flow in a curved two-dimensional throat is considered. The approximate calculation is based on the full nonlinear inviscid equations and an integral continuity condition. Numerical results are presented in the form of curves which permit the determination of the flow in a nozzle of specified geometry. Analytical results reduce after linearization to those of Sauer for the limiting case of a symmetric channel.
An Experimental Study of the Turbulent-Flow Boundary-Layer Development in Smooth Annuli
Authors: Okiishi T. H. , Serovy G. K.
Published: November 2011

This investigation was concerned with the turbulent flow with negligible heat transfer of a Newtonian fluid in the inlet region of smooth, concentric, constant-area annuli. Experimental mean-velocity profiles, static-pressure gradients, boundary-layer thickness parameters, and local friction factors were determined for airflow in annuli with radius ratios of 0.344 and 0.531. Each annulus was studied with both square-edged and rounded entrances. Flow separation caused by the abrupt change in area of the square-edged entrance resulted in skewed velocity profiles near the inlet. Consequently, no conventional boundary-layer growth occurred in the square-edged-entrance annuli. Further downstream, the skewness disappeared, and typical fully developed mean-velocity profiles were obtained. The turbulent mixing of fluid near the square-edged entrance appeared to have a stabilizing influence on the flow downstream. Conventional boundary-layer growth occurred in the rounded-entrance annuli since the gradual inlet produced a flat velocity profile at the beginning of the constant-area section. Velocity profiles, shape factors, displacement thicknesses, and local friction factors were appreciably affected by the transition from laminar to turbulent flow that occurred in the boundary layers. Further, fully developed velocity profiles were not obtained in the lengths tested.
Impact Techniques for the Study of Physical Properties of Solids Under Shock-Wave Loading
Authors: Graham R. A.
Published: November 2011

Measurements of various physical properties of solids while they are subjected to shock-wave loading from precisely aligned projectile impacts are described in order to illustrate the unique features and capabilities of the impact experiment. Results and experimental techniques are shown for the measurements of: (1) the piezoelectric coefficient of X-cut quartz from 2.6 to 25 kbar, (2) the permittivity change of 60 deg orientation sapphire from 20 to 100 kbar, (3) the resistance of [111] germanium which gives resistivity data in the elastic range and permits identification of the solid-solid phase transition at about 120 kbar, and (4) the compressibility of ferromagnetic fcc 30 Ni-70 percent Fe from 4 to 50 kbar which permits identification of the pressure-induced Curie point transition and a complete thermodynamic description of the transition.
Cavitation Hysteresis
Authors: Holl J. William , Treaster A. L.
Published: November 2011

In many cases, cavitation disappears at higher pressures than those at which it first appears. A measure of this cavitation hysteresis is the cavitation-delay time which tends to decrease with an increase in velocity, size, dissolved air content, or liquid tension. Cavitation hysteresis is a random phenomenon and is also dependent upon flow history and surface characteristics. Liquid tensions of one atmosphere are quite common and tensions of two to three atmospheres may be sustained for several seconds.
Decay of Turbulence in Axisymmetric Wakes
Authors: Hwang N. H. C. , Baldwin L. V.
Published: November 2011

Turbulent wakes formed downstream of flat, circular disks were surveyed with hot-wire anemometers in a low-speed wind tunnel. Three regions were discernible in the wake. Between the disk and x = 50 disk diameters D downstream, the turbulence was highly anisotropic and new turbulence was generated locally. An approximate similarity region (100 ≲ x/D ≲ 400) existed where isotropic turbulence relations were adequate for estimating decay. The far downstream wake (x/D ≳ 400) was highly intermittent throughout; the decay rate lessened in this final period. Over a 4-fold range of disk size and a 7 1/2-fold range of mean flow velocity, Taylor’s microscale was correlated by the mean residence time x/U∞; this relation was independent of disk size.
Experimental Observations on the Flow Past a Plano-Convex Hydrofoil
Authors: Wade R. B. , Acosta A. J.
Published: November 2011

Some new measurements and observations on the noncavitating and cavitating flow past a plano-convex hydrofoil are presented. Under some conditions of partial cavitation, strong, periodic oscillations both in the cavity length and forces exerted on the hydrofoil are observed. The reduced frequency of oscillation depends upon the cavitation number and angle of attack; it also depends somewhat on tunnel speed for the lower angles of attack but becomes substantially independent of speed for the highest angle. The peak-to-peak magnitude of the force oscillation can amount to about 20 percent of the average force.
Phase Trajectory Construction of High-Order, Nonlinear, Time-Varying, Nonautonomous Systems
Authors: Reis G. C.
Published: November 2011

A graphical procedure for constructing the time response of a system from its phase-plane trajectory is described. From this, a graphical solution of the equation x¨ + θ(x˙)g(x) + φ(x˙) + h(x) = F(t) is presented. The construction procedure for the equation x¨ + φ(x˙) + c(t)X(x) = F(t) is detailed as a special case of the more general form x¨+a(t)M(x)N(x)˙+θ(x)˙g(x)+b(t)Q(x)˙+φ(x)˙+c(t)X(x)+h(x)=F(t) which can also be solved in a similar fashion. The extension of these techniques to higher-order systems is presented.
Functional Representation of Nonlinear Systems, Interpolation and Lagrange Expansion for Functionals
Authors: Gorman D. , Zaborszky J.
Published: November 2011

The paper consists principally of three parts. In the first, an original analytic representation is introduced for systems where differential equations are available. In the second, the structure of the functional is analyzed with nonzero initial conditions. The third introduces functional representations for systems described by past measured input-output records.
A Technique of Quasi-Optimum Control
Authors: Friedland B.
Published: November 2011

To find the optimum control law u = u(x) for the process x˙ = f(x, u), the Hamiltonian H = p′f is formed. The optimum control law can be expressed as u = u* = σ(p, x), where u* maximizes H. The transformation from the state x to the “costate” p entails the analytic solution of the nonlinear system: x˙ = f(x, σ(p, x)); p˙=−fx′p with boundary conditions at two points. Since such a solution generally can not be found, we seek a quasi-optimum control law of the form u = σ(P + Mξ, x), where x = X + ξ with ‖ξ‖ small, and X, P are the solutions of a simplified problem, obtained by setting ξ = 0 in the above two-point boundary-value problem. We assume that P(X) is known. It is shown that the matrix M satisfies a Riccati equation, −M˙ = MHXP + HPXM + MHPPM + HXX, and can be computed by solving a linear system of equations. A simple example illustrates the application of the technique to a problem with a bounded control variable.
Parameter Representation of Low-Temperature Yield Behavior of Body-Centered Cubic Transition Metals
Authors: Bennett P. E. , Sinclair G. M.
Published: November 2011

In the low-temperature range, the engineering yield strength of polycrystalline bcc metals can change by a factor of 10 or more with serious consequences appearing in the form of catastrophic brittle fracture. Engineering variables known to have an important effect on the yield behavior are state of stress, temperature, loading or strain rate, composition, and microstructure. For iron, chromium, molybdenum, and tungsten, it is shown that yield behavior can be represented by a single-valued relation between two dimensionless parameters.
Lubrication Review: A Digest of the Literature for 1964
Authors: Hartung H. A. , Hingley C. L. , Zogbaum R. F. , Sneck H. J. , Rowe C. N. , Bowers R. C. , Wojtowicz W. J. , Hopkins Vern
Published: November 2011

The volume of lubrication literature continued to expand, reflecting the increased experimental and theoretical attention being given this discipline; this year’s Digest reviews more than five times the number of papers covered in the first Digest (for 1949).
Wall Stall in Compressor Cascades
Authors: Horlock J. H. , Louis J. F. , Percival P. M. E. , Lakshminarayana B.
Published: November 2011

The “wall stall” in compressor cascades has been observed by many research workers. There is a region of high loss in the corner bounded by the end wall and the suction surface of a blade. It is the separation of the flow in this region which is largely responsible for the increase in the axial velocity across the midspan section of the blades when there is no end-wall suction. It is important to differentiate between this wall stall and the two-dimensional stall of the blading. The work on wall stall described in the paper was carried out at the University of Cambridge and the University of Liverpool in the period 1955-1962.
Creep-Rupture Properties of 1.25 Cr–0.5 Mo Steel After Service at 1000 Deg F
Authors: Cullen T. M. , Rohrig I. A. , Freeman J. W.
Published: November 2011

Specimens of 1.25 Cr–0.5 Mo steel which had been exposed for prolonged times at 1000 F under ASME Boiler and Pressure Vessel Code allowable stresses were rupture tested in order to evaluate the influence of service on subsequent elevated-temperature properties. Specimens were tested as-removed from service and after reheat-treatment. The prolonged service drastically reduced short-time rupture properties but did not have any significant influence on the expected long-time rupture strength. Reheat-treatment restored the short-time strength to a high level.
Optimal Bounded Control of Linear Sampled-Data Systems With Quadratic Loss
Authors: Deley G. W. , Franklin G. F.
Published: November 2011

A method is presented for the computation of optimal control for linear sampled-data systems when the control variable is a bounded scalar. It is shown that for this problem the optimal control is a piecewise linear function of the state and may be computed by piecewise iteration of suitable recurrence relations. The optimal control is presented in terms of the control coefficients (matrices) and the regions to which they apply. No solution other than computer storage is suggested for the synthesis of these controls. In the second section of the paper, it is shown that the method applies with trivial modification to the random-input, random-observation noise case. The optimal control law has the same form as the deterministic case with the conditional expectation used in the control law in place of the stale itself. A simple deterministic example computed on an IBM 1620 is presented. As might be expected, the computer capacity required for the problem is intermediate between the unbounded control case, where the control is linear, and more general problems.
Gas-Lubricated Stepped Thrust Bearing—A Comprehensive Study
Authors: Wildmann M. , Glaser J. , Gross W. A. , Moors D. E. , Rood L. , Cooper S.
Published: November 2011

The theoretical part of this report is based on Ausman’s analysis [2] of gas-lubricated stepped slider bearings, but presented in simpler form. Experimental data in this paper verify Ausman’s solution. A correlation is attempted, and the design procedure given herein is based upon a combination of the Ausman theoretical method and these experimental studies.
Power-Transfer Characteristics for Compressible Flow From a Stationary Nozzle to a Detached Receiver
Authors: Weng Cheng-Kuo
Published: November 2011

Theoretical and experimental investigations have been made of the compressible flow power-transfer characteristics from a stationary nozzle to a detached receiver. The effect of the nozzle and receiver geometrical configuration on the power-transfer characteristics has been studied. Experimental data are included to illustrate the characteristic behavior of the system and to explain how the geometrical configuration should be chosen to obtain the best power recovery. Results and conclusions reached from this study can be used to approximate the compressible flow power transfer from a stationary nozzle to a rotating receiver.
Low Cycle Fatigue Evaluation of Inconel 713C and Waspaloy
Authors: Morrow JoDean , Tuler F. R.
Published: November 2011

Completely reversed axial fatigue results are reported for Waspaloy and Inconel 713C at room temperature. Fatigue strength and ductility are evaluated using power functions of the fatigue life. The exponents and coefficients of these two equations are looked upon as four fatigue properties of the material. They appear in the equations which are developed to relate cyclic stress, plastic strain, total strain, plastic strain energy per cycle, total plastic strain energy to fracture, and fatigue life. These equations and the four fatigue properties permit the evaluation of the relative fatigue resistance of various metals at different fatigue lives when subjected to strain, stress, or plastic strain energy cycling. The “best” selection of material to resist fatigue is found to depend on the type of cycling and the desired life. At room temperature, the wrought Waspaloy is found to be more fatigue resistant than the cast Inconel 713C, particularly in resisting strain or plastic strain energy cycling in the low cycle fatigue region. For longer lives the difference in fatigue resistance between the two diminishes, especially for stress cycling. It is believed that the method of fatigue evaluation used here is generally applicable to the engineering problem of material selection to resist fatigue, and should in some cases replace methods based on conventional rotating bending fatigue tests which only evaluate the fatigue strength at long lives.
Biaxial Brittle Fracture Tests
Authors: Manjoine M. J.
Published: November 2011

The brittle fracture characteristics of a particular steel can be evaluated by a notched specimen if sufficient triaxial tension or constraint is developed at the notch. A biaxially loaded notched test specimen has been developed in which a crack-like notch was prepared by compressing a V-notch. Data obtained with this specimen are compared to those of two other types of test and found to be more consistent and reliable. This test specimen can also be used in a neutron radiation program for determining the change in Brittle Fracture characteristics of stressed and unstressed materials.
Correlation of Fatigue Tests of Thick-Wall Cylinders Subjected to Repeated Internal Pressure
Authors: Hannon B. M.
Published: November 2011

This paper is intended to demonstrate an engineering approach to the field of high-pressure fatigue. A further intention is to stimulate thought toward the farmation of a correction equation, which may be made by applying a series of approximate correction factors to a state-of-stress equation. It is possible that the fatigue limit or “endurance pressure” of thick-walled cylinders of various wall ratios may be estimated by using such a correction equation.
Significance of the Vortex Breakdown Phenomenon
Authors: Benjamin T. B.
Published: November 2011

The essential points in the author’s published theory of this phenomenon are summarized, and their implications with regard to longitudinal vortex flows in general are reviewed. The primary aim is to emphasize the physical principles which underlie the theory, and most of the mathematical details are passed over here. It is proposed that these principles serve to rationalize a wide variety of possible behavior in swirling flows.
Lubrication Review: A Digest of the Literature for 1963
Authors: Peterson M. B. , Timkens T. E. , Brown R. D. , Burton R. A. , Klaus E. E. , Wojtowicz W. J. , Villforth F. J.
Published: November 2011

In this review the developments in the fields of lubricants, friction, and bearing materials have been summarized by various authorities in each particular field. The review covers the period from June to December, 1963. The developments in bearings and gears will be published at a later date. Much of the published work is concerned with high temperature and vacuum conditions. However, it is of interest to note the large increase in the published work in solid lubricants over that of previous years.
Generation of Precise Reference Pressures Up to 15,750 Psi
Authors: Ess J. O.
Published: November 2011

This paper covers the design and the operational and performance characteristics of a precision pressure generation system utilizing a controlled-clearance type of piston gage. Programmed computer outputs for generating precise pressures automatically in increments smaller than 1 psi over the entire system range have been used to eliminate computational requirements and to generate a large number of pressures rapidly. Piston fall rates have been controlled using constantly varying jacket pressures to maintain sensitivity and flotation requirements, and to keep wear down to a minimum. Experience regarding constancy of pressure output over a period of three years is covered. The amount of actual time in use for the system is well over a thousand hr.
A Variational Principle Applied to the Plane Slider Bearing
Authors: Maday Clarence J.
Published: November 2011

A minimum principle from hydrodynamics is applied to the one-dimensional plane slider bearing which is provided with a self-seeking pivot mechanism. An analysis was made in which a certain integral was minimized subject to the constraint that the load, speed, and viscosity were held fixed. This analysis showed that this corresponded exactly to that combination of minimum film thickness and inclination which would minimize the power loss subject to the above-mentioned constraint. It was also found that, in order to satisfy the minimum principle, there exists a definite numerical ratio between the slider inclination and the nondimensional minimum film thickness. This, in turn, fixed the pivot location relative to the length of the slider.
Poppet Valve Stability
Authors: Funk James E.
Published: November 2011

The analysis presented in this paper shows that poppet valve instability can be caused by interaction of the fluid delivery line dynamics with those of the spring-mass of the valve. The critical frequency in the system is the first harmonic of the delivery line higher than the natural frequency of the valve spring-mass. A stability criterion is derived which relates the design parameters of the valve to those of the system in which it must operate and methods of stabilizing the operation are suggested.
The Turbulent Flow at the Plane of Symmetry of a Collateral Three-Dimensional Boundary Layer
Authors: Pierce F. J.
Published: November 2011

Momentum integral equations for the turbulent flow at the plane of symmetry of a three-dimensional boundary layer are rigorously derived. The use of orthogonol curvilinear coordinates allows a simple physical interpretation to be given to the terms of the resulting equations. Evaluation and comparison are made between the derived results and earlier works in Cartesian sets and ambiguities are discussed. Results of an experimental program are reported for the case of a plane of symmetry flow in a collateral three-dimensional turbulent boundary layer wherein four different momentum integral equations are examined in predicting boundary-layer growth. As an aside, two common variations of shape parameter equations were also tested to determine their adequacy in application to this case.
Expansion of a Very Low Quality Two-Phase Fluid Through a Convergent-Divergent Nozzle
Authors: Starkman E. S. , Schrock V. E. , Neusen K. F. , Maneely D. J.
Published: November 2011

Flow in de Laval nozzles of high pressure, low-quality steam-water mixtures was investigated to determine the resulting mass flow rates and to acquire design criteria information. Qualities ranged from 0 to 20 percent and pressures up to 1000 psia. Comparisons of the experimental data to three simple models: (a) isentropic expansion; (b) frozen composition; and (c) slip flow, showed satisfactory correspondence at all conditions except for qualities very close to saturated liquid. Observation was made that a condition similar to shock resulted when the nozzles were overexpanded.
Comparison Between Theories and Experiments for the Threshold of Instability of Rigid Rotor in Self-Acting, Plain-Cylindrical Journal Bearings
Authors: Pan C. H. T. , Sternlicht B.
Published: November 2011

The threshold of half-frequency whirl for a rigid rotor in self-acting, plain-cylindrical journal bearings is analyzed by several methods, and the results are compared. The correlation among the various approaches appears to be good. The simplest method of analysis is, therefore, used for comparison with experimental data. Experimental results showing the effect of bearing length and bearing load are compared with theory. The influence of bearing length on the threshold speed follows closely the trend of the calculated results; however, the experimental threshold speeds are always a little higher. In comparing the effect of bearing load it is seen that the calculated threshold speed is consistently somewhat over-pessimistic, but the influence of rotor inclination is in very good agreement with experimental data. The methods presented in this paper can be used readily in design to insure stable operation with plain-cylindrical journal bearings.
Static and Dynamic Characteristics of Self-Acting, Partial-Arc, Gas Journal Bearings
Authors: Wernick R. J. , Pan C. H. T.
Published: November 2011

The Reynolds equation applicable to a self-acting partial-arc gas journal bearing is perturbed in terms of the compressibility number Λ. The resulting set of equations is then put into a standard form and Galerkin’s method is used to obtain bearing loads and stability derivatives. These results are expressed in a power series in Λ.
Optimum Control of Distributed-Parameter Systems
Authors: Wang P. K. C. , Tung F.
Published: November 2011

This paper presents a general discussion of the optimum control of distributed-parameter dynamical systems. The main areas of discussion are: (a) The mathematical description of distributed parameter systems, (b) the controllability and observability of these systems, (c) the formulation of optimum control problems and the derivation of a maximum principle for a particular class of systems, and (d) the problems associated with approximating distributed systems by discretization. In order to illustrate the applicability of certain general results and manifest some of the properties which are intrinsic to distributed systems, specific results are obtained for a simple, one-dimensional, linear-diffusion process.
The Relation Between the Rubbing Interface Temperature Distribution and Dynamic Thermocouple Temperature
Authors: Shu H. H. H. , Gaylord Eber W. , Hughes W. F.
Published: November 2011

The dynamic thermocouple formed by the moving junction of two dissimilar metals is known as the Herbert-Gottwien thermocouple. It is analyzed for the case of two semi-infinite bodies having a continuous rectangular rubbing contact area. Methods for determining the interface temperature after Chao and Trigger are presented; and the dynamic thermocouple, or Herbert-Gottwien temperature, is related to the temperature distribution. It is found that the dynamic thermocouple temperature is a weighted average of the latter and the weighting function is independent of temperature distribution and depends only on the geometry of the contact area. The weighting function assumes a higher value toward the periphery than it does in the interior of the contact area. The above ambient dynamic thermocouple temperature is found to be directly proportional to a geometry factor of the contact area and to the total heat flux across the contact area.
Precise Measurement and Prediction of Bulk-Modulus Values for Fluids and Lubricants
Authors: Klaus E. E. , O’Brien J. A.
Published: November 2011

A series of precise determinations has been conducted with the PRL Bulk Modulus Apparatus designed to measure isothermal secant bulk modulus over the range of 0 to 10,000 psig and 32 to 350 F. These measurements have been used as the basis for the development of a series of correlations between isothermal secant, isothermal tangent, and adiabatic tangent bulk-modulus values. The validity of these correlations has been demonstrated by the use of measured and calculated bulk-modulus values obtained from several literature references.
On Gas Lubrication in Turbulent Regime
Authors: Constantinescu V. N.
Published: November 2011

This paper analyzes first the transient conditions from laminar to turbulent regime for gas lubricated bearings. Then the pressure equation is deduced for self-acting gas-lubricated bearing by using Prandtl’s mixing length theory. A simple method for determining the pressure and the operating characteristics for bearings operating at high numbers H is given, based on an analogy with the corresponding laminar case. The pressure equation is also given for thrust and journal gas bearings under variable forces and velocities. The last two sections examine the influence of turbulence in externally pressurized gas bearings and the influence of inertia forces, respectively. The results obtained show that the turbulence does not alter qualitatively the operation conditions of gas-lubricated bearings. Moreover, the influence of turbulence in self-acting gas bearings is less important than in the case of liquid-film lubrication and even negligible when the bearing operates at high numbers H.
Performance of Centrally Pivoted Sector Thrust-Bearing Pads—Sea Trials Aboard USS Barry (DD 933)
Authors: Elwell R. C. , Gustafson R. E. , Reid J. C.
Published: November 2011

This paper is the third in a series which presents the results of a study of main marine propulsion bearings of the conventional pivoted-pad, hydrodynamic type. It presents a description of tests conducted at sea on the main propulsion thrust bearings of the destroyer USS Barry (DD 933). Steady steaming tests in both calm and rough water are reported, for the full range of design speeds and loads. Data taken in these tests are compared to the values predicted by the analytical results of the first two papers in this series. These earlier papers analyzed the performance of such bearings under conditions of constant speed and load. Data from simultaneous measurement of 59 temperatures and 18 oil-film thickness gages is presented.
Friction Factors for Fully Developed Turbulent Flow in Ducts With and Without Heat Transfer
Authors: Maurer G. W. , LeTourneau B. W.
Published: November 2011

Tests were performed with water flowing vertically upward through a 0.087-in. × 1-in. × 27-in. long rectangular channel to determine friction factors with and without heat transfer. The following range of variables was covered: Mass velocities: 0.60 × 106 to 4.0 × 106 lbm/hr-ft2; Heat flux: 0 to 1.6 × 106 Btu/hr-ft2; Inlet temperature: 59 to 510 deg F; Pressures: 300 to 2000 psia. The isothermal data confirmed the use of the hydraulic equivalent diameter with the conventional circular tube friction factors for narrow rectangular channels at Reynolds numbers from 4 × 103 to 5 × 105. Using the results of the heated tests and the data existing in the literature, a general correlation was formulated which correlated the data for both water and air.
A Study of Pressure Homogeneity in the Hexahedral Anvil High-Pressure Apparatus
Authors: Samara G. A. , Henius A. , Giardini A. A.
Published: November 2011

A study of operational characteristics and stress distribution in a large volume hexahedral apparatus has been made. Pyrophyllite containers with integral preformed gaskets were found to be superior to plain blocks. Pregasketing reduced material flow and sample deformation, increased by over 100 percent the central region of the container over which little or no deformation occurs, and greatly increased anvil life. Even so, large pressure gradients still existed within the container. These gradients become more severe the higher the pressure. Pressure efficiency and distribution were appreciably changed by varying the length and thickness of preformed gaskets. Built-in metal intensifiers increased pressure efficiency by up to 30 percent. The inclusion of a metal heater tube had no measurable influence on pressure gradients. Cycling decreased the applied load required to reach a given pressure only if the load was not allowed to fall below a certain minimum. This is attributed to the ability of pyrophyllite to remain static while supporting large stress gradients.
The Linearized Theory of a Supercavitating Hydrofoil With a Jet Flap
Authors: Ho Hung-Ta
Published: November 2011

A theoretical analysis is carried out for the steady cavity flow about thin hydrofoil sections at small incidence α, at the trailing edge of which a thin jet emerges at a small deflection τ. The flow is assumed to be inviscid and incompressible and the cavitation number is taken to be zero. The jet is assumed so thin that it can be considered as a vortex sheet across which the velocity is discontinuous. For the case of a flat plate, expressions have been obtained for lift, drag, pressure distribution, pitching moment, the jet shape, and the cavity shape. Numerical calculations are made for a number of jet momentum-flux coefficients CJ lying between 0.01 and 5.
Hill Climbing Methods for the Optimization of Multiparameter Noise Disturbed Systems
Authors: Kushner Harold J.
Published: November 2011

Modifications of the statistical technique of Stochastic Approximation are used as a means of experimentally optimizing multiparameter systems on which the only available information is obtained from noise perturbed samples of the performance. Varieties of both Gradient and Relaxation Processes are considered and methods are given for experimentally adjusting certain undetermined process constants for most rapid (mean square) convergence to the optimum parameter settings.
The Design of Optimum Controllers for Linear Processes With Energy Limitations
Authors: Friedland Bernard
Published: November 2011

A special-purpose analog computer which can be used as the optimum controller for linear processes with energy-limited control inputs is described. The computer may be used to force the process state to a desired state in minimum time; or to minimize the terminal error at a specified time; or to minimize the energy consumption, if the error can be reduced to zero in the specified time. Continuous-time and discrete-time processes are both considered.
A Unified Theory of Cavitation Damage
Authors: Thiruvengadam A.
Published: November 2011

The Cavitation Damage Number proposed by the author has been modified to incorporate the concept of strain-energy instead of the dynamic yield stress of the material. The correlation between the Cavitation Damage Number and the Number of Cavities has been extended to different materials and different sizes. A third nondimensional number known as the Inception of Damage Number has been derived and correlated with the critical cavitation parameter. Detailed investigations in the threshold zone indicate the validity of the functional relationship between the critical cavitation parameter and the Inception of Damage Number. In this paper, the part played by each parameter is analyzed and some of the experimental results arrived at by earlier investigators are explained in the light of the present theory.
Nonlinear Viscosity Effects in Slider Bearing Lubrication
Authors: Ng C. W. , Saibel Edward
Published: November 2011

The relationship between stress and rate of strain for a non-Newtonian fluid with pseudoplastic behavior is assumed to be a cubic power series. Under this assumption a solution of the slider bearing without side leakage can be obtained using a perturbation technique. The solution turns out to be relatively simple in form in contrast to what results when a general power law is used.
Gyroscopic Coupling in Space Vehicle Attitude Control Systems
Authors: Cannon Robert H.
Published: November 2011

The problem of controlling the attitude of a space vehicle is unusual in several respects. While the required precision may be extreme—less than 0.1 second of arc in certain cases—the required response time may often be very slow, measured in minutes or hours. Vehicles weighing tons may have to be controlled by inch-ounces of torque, and control energy is at an extreme premium. The present paper discusses the effects, on performance, of inter-axis coupling due to internal spinning parts. A de-coupling computer to nullify gyroscopic torque is described, and its utility is evaluated. The computer is found to improve precision, but to reduce energy consumption only in certain cases. It is shown that by postulating such a computer the performance of a given system may be accurately evaluated on the basis of much simpler single-axis relations, even though strong coupling is present. Specifically: (1) It is shown that the best available performance is established by postulating de-coupling control; and (2) a method is given for determining the amount by which a conventional system will fail to achieve that performance.
Influence of Ductility on Creep Rupture Under Multiaxial Stresses
Authors: Sawert W. , Voorhees H. R.
Published: November 2011

Creep-rupture times at 1200 and 1400 deg F were compared for notched versus unnotched bars and for thin-walled tubes in uniaxial tension versus combined tension and internal pressure to give a 1:1 ratio of longitudinal and transverse principal stresses. Relative response to multiaxial stresses of cast DCM alloy with low ductility was not essentially different from that of Rene´ 41 alloy with higher ductility. Creep rupture times of the tubular specimens under combined stresses correlated better in terms of the shear stress invariant than of maximum principal stress.