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RESEARCH PAPERS

J. Basic Eng. 1960;82(1):1-6. doi:10.1115/1.3662523.

The object of this paper is to investigate the effects of cavitation on the discharge coefficient of sharp-edged orifice plates with reference to various degrees of cavitation as defined by a cavitation number. The experimental data described in this paper substantiate the fact that cavitation can exist to a minimum cavitation number of 0.2 without introducing errors in the orifice discharge coefficient in excess of the normal expected accuracy. In addition to this, it was found that the use of air-inhalation to suppress the vibration and noise from the cavitation had no effect on the discharge coefficient.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):12-16. doi:10.1115/1.3662499.

A special apparatus is designed to measure the oil-film thickness between two stationary disks (simulating meshing gear teeth) by applying a-c or d-c potential across the film and measuring its resistance for given gap between the disks. Experiments show that the treatment of oil with additive (sodium-petroleum sulphonate in this case) may well lead to a considerable increase in its electrical conductivity, and to a substantial improvement in the independence of the oil-film resistance of the electrical history and temperature of the oil. A reliable relationship could eventually be obtained between the oil-film resistance and relevant thickness. Test results are employed in investigating the behavior of the oil film in a rotating-disk testing machine developed by the authors for studying the performance of meshing gear teeth with adequate supply of lubricant.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):19-28. doi:10.1115/1.3662522.

A testing machine has been designed to investigate the performance of the lubricating oil film between two independently driven circular disks in line contact under conditions of combined rolling and sliding, in an endeavor to study the behavior of meshing gear teeth with adequate supply of lubricant. Test results show that the ratio of sliding to rolling velocity is a prime factor in the behavior of rotating disks. Values of this ratio equal to zero and unity (conditions of pure rolling and pure sliding, respectively) give rise to critical changes in the performance of the disks, being most favorable, from a lubrication viewpoint, at pure rolling (i.e., at the gear pitch line) and least favorable at pure sliding where scuffing of surfaces may well be expected Recent theoretical investigations do not seem to be able yet to account for salient results obtained in the present study. Further work on the subject is proceeding.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):29-34. doi:10.1115/1.3662549.

The voltage drop across thin oil films when a constant current of 1 amp is passed, i.e., the discharge voltage, is used to measure the oil-film thickness between loaded gear teeth while running. It is found that the thickness at the pitch line is between 1 and 4 × 10−4 in., which varies slightly with the viscosity and rather more strongly with load. The thickness at the tips and roots is very dependent on the tip relief. The conditions here may explain the difference between disk and gear tests. These experimental values are compared with theoretical work and are shown to be of the same order of magnitude.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):35-45. doi:10.1115/1.3662552.

The classical filtering and prediction problem is re-examined using the Bode-Shannon representation of random processes and the “state-transition” method of analysis of dynamic systems. New results are: (1) The formulation and methods of solution of the problem apply without modification to stationary and nonstationary statistics and to growing-memory and infinite-memory filters. (2) A nonlinear difference (or differential) equation is derived for the covariance matrix of the optimal estimation error. From the solution of this equation the co-efficients of the difference (or differential) equation of the optimal linear filter are obtained without further calculations. (3) The filtering problem is shown to be the dual of the noise-free regulator problem. The new method developed here is applied to two well-known problems, confirming and extending earlier results. The discussion is largely self-contained and proceeds from first principles; basic concepts of the theory of random processes are reviewed in the Appendix.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):46-50. doi:10.1115/1.3662553.

Feedback can be used as a means of realizing Shannon-predicted errorless capacity of a noisy communication channel. On the other hand, Shannon’s information theory can be used as a guide for rating feedback control systems as well as selecting system components. A brief summary of the former aspect and the results from some preliminary investigations of the latter aspect are presented. Included topics are calculations of required information capacities of control systems from input characteristics and fidelity requirements, required information capacities of system components, and calculation of information capacities of system components from saturation limits, threshold levels, and transfer functions.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):51-60. doi:10.1115/1.3662554.

The transfer functions obtained by dynamic analysis of one shell pass and 2, 3, 4, [[ellipsis]].., 2n, 2n + 1 tube-pass heat exchangers as a distributed parameter system are presented in dimensionless forms. The heat-exchange processes are found to be governed by the third-order characteristic equations with complex coefficients, and can be solved numerically using a graphical method. The numerical examples are presented to show the clear difference of frequency response for such cases when no solid capacity exists. The analog computer and the experimental results are found to be in good agreement with the theoretical results.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):66-72. doi:10.1115/1.3662557.

A simple nonlinear scheme for controlling a second-order rate-type servomotor is described. This scheme is referred to as “bang-bang” control since the input to the servomotor is made to “bang” from its maximum value in one direction to its maximum value in the other direction depending only on the sign of an error signal. This bang-bang system oscillates in a continuous high-frequency, low-amplitude limit cycle. The nature of this limit cycle is studied by the describing function approximation and by an exact method. The step and frequency response characteristics of the bang-bang system are discussed and compared with the characteristics of a simple linear system. It is shown that many aspects of the behavior of the bang-bang system can be predicted from rather simple considerations.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):73-80. doi:10.1115/1.3662559.

Almost all conventional servovalves operate on the principle of controlling the position of a four-way or three-way valve made with very high precision with the hope that the flow rate will follow accurately the input signal to the valve. In this paper, an entirely new approach to the servovalve design is presented. A flow signal instead of valve position is used in the feedback loop. This design eliminates the necessity of a high precision valve, gives a greater length of the life expectancy of the valve, and minimizes the effect of load variation as well as supply pressure variation. Dynamic analysis and test results of the flowmeter and the complete valve are given.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):81-86. doi:10.1115/1.3662560.

A fast-response, unique thermoelement combination of platinum-15 per cent iridium and palladium, whose emf output is about three fourths that of Chromel/Alumel at 2000 F (1093 C), has been found reliable from 1800 to 2300 F (982 to 1260 C) for more than 400 hours in a combustion atmosphere. A new, stable nickel-4.3 per cent silicon matching-lead-wire alloy was prepared for use up to an ambient temperature of 1400 F (760 C). Additional tests provided the best choice of insulation, thermocouple dimensions, sheath material, connectors, and harness design for aircraft jet engines. While it has heretofore been impractical or very difficult to determine turbine-inlet temperatures above 1600 F (871 C), this system is capable of measuring directly the most critical of all operational variables and accordingly allows safe potential increases in engine performance.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):87-95. doi:10.1115/1.3662561.

A procedure is developed, based on Couchy’s residue theorem, for bounding the undamped natural frequency, damping ratio, and real part of the roots of the characteristic determinant associated with a multicoupled system with several inputs and outputs. The method can lead to a locus of the roots as one or more parameters are varied. The underlying theory is developed and a numerical illustrative example is included.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):96-102. doi:10.1115/1.3662562.

A precise characterization of the thermal resistance of clothes requires an accurate description of the static and dynamic thermal characteristics of the human-heat source. Experimental measurements on the human have revealed a frequency spectrum of sustained thermal power oscillations that mask theoretical long-time equilibrium adjustments. This points to the number of degrees of freedom that must be involved in the thermoregulation of the human, and the specific nonlinear characteristics of the system. Therefore at best, a resistance model for clothes is possible only as an ohmic relation among time-averaged equilibrium values, and for a specific mode of operation of the system. The validity of this hypothesis, however, has not been proved.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):103-112. doi:10.1115/1.3662494.

Quantitative measurement on the human in the so-called evaporative, vasomotor, and metabolic control regimes has revealed frequency spectrum of sustained thermal power oscillations with approximate periods of 2, 7, 35 min, and 3 1/2 hr independent of the regime. Step function adjustments take place with a time constant of about 7 min. It is believed that the 3 1/2 hr cycle represents the shortest equilibrium cycle. The hypothesis that it might be possible to measure the resistance of clothing as an ohmic relation among time-averaged equilibrium values, and for a specific mode of operation of the system has now been put in rational context in the time domain. Two equilibrium modes of the human system were explored. The active mode of operation of the system, to which the resistance concept of clothes is most applicable, is as a feedback system in which the extremities are used as error indicators of deviations from a comfort level set point. In response to deviations, the human feeds back a signal to generate an activity level in which only internal work—immediately degraded into heat—is done to maintain the comfort level. This is referred to as the comfort mode of operation of the system. Another “survival” mode of operation of the system is also described.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):113-119. doi:10.1115/1.3662496.

Problems of process optimization and in particular automatic optimization are currently being approached from many different directions. Investigations in process control and instrumentation, studies in statistical methods for the design of experiments for obtaining optima, studies on noise spectra and on numerical maximization subject to restraints as represented by linear and nonlinear programming, all throw light on the directions in which we must advance.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):120-129. doi:10.1115/1.3662497.

An analysis for predicting the secondary and primary flows and the thrust coefficient of ejector nozzles is presented. Particular attention is given to the diverging shroud ejector in which the throat of the secondary stream is formed at a small distance down-stream of the primary nozzle exit; i.e., near the plane of the minimum shroud area. The basic assumption in the analysis is that the shroud is sufficiently short so that the mixing of the two streams is incomplete, and that both streams have isentropic cores. The momentum thickness of the mixing region is obtained from the momentum-integral equation for the turbulent mixing region assuming that momentum and temperature diffuse at the same rate. The momentum thickness at the nozzle exit is related to the initial momentum thickness created by the wall separating the two streams. The exit-momentum thicknesses of the mixing region and the wall are used to obtain the actual thrust coefficient. Experimental data on primary-secondary flow properties and thrust coefficients of a divergent-shroud ejector nozzle show good correlation with the theory.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):131-140. doi:10.1115/1.3662501.

The results of extensive experimental studies to determine the pressure losses for turbulent flow in smooth pipe bends of circular cross section are presented in this paper. To make the data usable in practical design problems, the results are discussed in relation to those found by previous investigators, and empirical formulas for the bend-loss coefficient are given. The general correlation of the test data appears to be as good as our present test information will permit.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):144-154. doi:10.1115/1.3662504.

Experiments were run on a poppet valve operating in hydraulic oil. The experimental values of the flow forces and discharge coefficients were about 25 per cent below the predicted theoretical values. Although there was some scatter in the values of discharge coefficients, there was good correlation for the flow forces. Flow forces are strongly influenced by the downstream configuration. The smaller the diameter of the downstream chamber, the higher the forces. A poppet configuration was designed and tested which virtually eliminated the flow forces.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):155-167. doi:10.1115/1.3662505.

The location and orientation of vanes in an annulus are established on the basis of two principles which result from a discussion of simple elbows. These principles are incorporated into a procedure for designing the diffuser vanes in the crossover passage between stages of a centrifugal compressor. To test the proposed design a low-speed model was built and tested and the results compared with a second model which represented a more conventional design.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):169-183. doi:10.1115/1.3662508.

The inception of cavitation on isolated surface irregularities imbedded in a turbulent boundary layer is investigated experimentally and theoretically. Two families of cylindrical roughness elements having constant cross sections are studied. One family has a circular-arc cross section. The other family has a triangular cross section and was selected to simulate the separating flow which is typical of an actual surface irregularity. The theoretical minimum-pressure coefficient for the circular-arc irregularities is determined as a function of the relative height of roughness for several values of the boundary-layer shape parameter. Cavitation tests in the water tunnels of the Ordnance Research Laboratory on roughness elements ranging from 0.002 to 0.5 in. in height indicate that the incipient-cavitation number of an isolated surface irregularity is dependent upon the relative height of roughness, the boundary-layer shape parameter, the velocity, and other variables as yet unknown.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):184-192. doi:10.1115/1.3662513.

The first stage in cavitation damage—indentation where cavitation bubbles collapse near the metal surface—was observed and measured by Knapp [1]. The author suggested that the high temperature of indentation points, caused by the absorption of work in their formation, should create conditions favorable to energetic local chemical action between water and metal. The brittle oxide films thus produced would be ruptured by later blows, resulting in erosion. Photomicrographs taken in monochrome and color show the form and texture of indentations with associated corrosive oxidation. Parallel experiments were made with toluene whose inertness permitted the elimination of chemical factors. The special features of the microscope technique employed to get the photographs are explained.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):195-200. doi:10.1115/1.3662521.

It is shown that a simple shock tube is capable of producing appreciable steady-flow rates through a short duct element, such as an orifice, a valve, or a screen. The flow upstream and downstream of the test element and, therefore, also the losses caused by the test element, can be calculated from known initial conditions in the shock tube and pressure measurements at one point upstream of the element. Experiments to determine the discharge coefficient of a sharp-edged orifice are described as an illustration of the method. The results are in good agreement with available steady-flow data.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):201-207. doi:10.1115/1.3662524.

A method of incompressible turbulent boundary-layer analysis based on the D parameter introduced by D. Ross is applied to conical-diffuser flow. The separation conditions are shown to depend on the initial momentum-thickness Reynolds number and a distance parameter involving the initial momentum thickness, the initial radius, and the diffuser length. Comparison with experimental information on diffuser separation indicates that the predictions are reliable, but conservative.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):210-215. doi:10.1115/1.3662529.

Problems of the molecular transfer of momentum and heat in a fluid between two concentric cylinders are often encountered in the field of lubrication. It is shown herein that these problems can be solved by a generalized Fourier analysis, and that, in particular, varying boundary conditions and nonhomogeneous terms in the diffusion equation which are time-dependent can be treated by the Duhamel method from the theory of the conduction of heat in solids. Heat generated by viscous shear, as well as that externally applied, is included in the analysis.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):217-230. doi:10.1115/1.3662532.

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a right-cylindrical chamber have been studied both experimentally and theoretically. In order to acquire further and systematic information pertinent to this problem, which has received much attention in the past, torque data were obtained over a range of disk Reynolds numbers from 103 to 107 for axial clearance-disk radius ratios s/a from 0.0127 to 0.217 for a constant small radial tip clearance and velocity and pressure data were obtained for laminar and turbulent flows. The existence of four basic flow regimes in the axial gap between the disk and casing wall was verified, and these regimes, the existence and extent of which are governed by the Reynolds number-axial spacing combinations, have been delineated. A new approximate theoretical analysis has accounted for axial-clearance effects for the case of separate boundary layers on the disk and end wall; this theory has been checked against test results. Velocity and pressure data have shown that the concept of a fluid “core” rotation in the case of separate boundary layers must be modified because of secondary flows and skewed boundary layers.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):233-246. doi:10.1115/1.3662539.

A study of the secondary flow type of three-dimensional turbulent boundary layer is presented. Two objectives are achieved: (a) A mathematical model of the relationship between the cross-flow and main-flow components of the velocity vectors of the layer is established. (b) By utilization of the model some of the relationships required to carry out a boundary-layer problem solution by the use of the momentum-integral equations are developed.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):140-142. doi:10.1115/1.3662502.
FREE TO VIEW
Abstract
Topics: Pressure , Pipe bends
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):142-143. doi:10.1115/1.3662503.
FREE TO VIEW
Abstract
Topics: Pressure , Pipes
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1960;82(1):192-193. doi:10.1115/1.3662515.
FREE TO VIEW
Abstract
Topics: Metals , Cavitation
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

ERRATA

Commentary by Dr. Valentin Fuster

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