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RESEARCH PAPERS

J. Basic Eng. 1961;83(3):317-327. doi:10.1115/1.3658953.

Physical evidence on stall inception from visual studies, mean-velocity-profile correlations, shear measurements, and fluctuations in separating boundary layers in the neighborhood of stall are discussed. Direct visual studies suggest that stall inception in the laminar boundary layer follows the classical model, but does not necessarily do so in the turbulent shear layer. It is useful to describe stall as a certain type of transition region, which can be long or short. Adoption of these ideas is shown to lead to better correlation of stall data and more complete understanding of available physical evidence. However, physical data on the relation between the various types of evidence in the turbulent case and their respective connections with the events in the transition region leading to stall are not presently complete. This suggests experiments of a certain type which should lead to further clarification of the process of stall inception in the turbulent boundary layer.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):328-332. doi:10.1115/1.3658954.

The momentum, continuity, and energy equations of the laminar incompressible boundary layer in a skew-linear co-ordinate system are similar in form to those in a rectangular co-ordinate system. This fact is used to generalize the requirements for similarity solutions in rectangular co-ordinates. The requirements for all possible similarity solutions of the boundary-layer and energy equations in skew-linear co-ordinates are presented. The usual Cartesian co-ordinate system is a special case of co-ordinate systems considered.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):333-339. doi:10.1115/1.3658957.

The motion of spherical particles injected into a cylinder of gas which rotates as a solid body has been studied. The particle trajectory is expressed explicitly as a function of two dimensionless parameters; an injection-velocity parameter and an inertial parameter which is roughly the ratio of centrifugal force to drag force on the particle. The main results are the dependence on particle size of the time for particles to be centrifuged and of deposition angle. These results indicate performance limitations for an idealized cyclone separator and a centrifugal particle-size analyzer. Experimental data are presented for an air centrifuge which was designed to approximate the analytical flow model. Reasonably good agreement with theoretically predicted deposition angles was found for spherical glass beads and irregularly shaped chalk crystals, even to Reynolds numbers in excess of the Stokes flow regime for which the analysis applies. Particles as small as 2 microns may be classified with the present centrifuge configuration; however, by modification it might be used to classify particles in the submicron-size range.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):341-348. doi:10.1115/1.3658961.

The calculation of a nonsteady flow discharging into the atmosphere, or into a large reservoir, is generally based on the assumption that the effective exit pressure is the same as if the flow were steady. In reality, however, the steady-flow boundary conditions are asymptotically approached after a disturbance produced by an incident wave, and recently published investigations provide a better approximation to these transient boundary conditions. Utilizing these results, one can compute the rate of discharge and compare it with the rate obtained in the conventional manner. The difference between the results of the two calculations is used to define a lag error in the conventional calculations. Examples for discharges through an open end and through a sharp-edged orifice indicate that the actual transient flow rate may deviate considerably from that computed on the basis of steady-flow boundary conditions.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):349-360. doi:10.1115/1.3658962.

Performance data and flow characteristics for subsonic two-dimensional plane-wall diffusers are presented for the following conditions. (a) Wall-length to throat-width ratios of 8.0, 12.0, and 48.0, (b) total divergence angles from 2.5 to 40 deg, (c) extremely thin inlet boundary layers to fully established channel flow, (d) a vaned diffuser with L/W1 = 8.0 and quite thick inlet boundary layers. Flow conditions and variations of flow regimes for L/W1 = 48.0 are compared. No real gain in recovery or pressure effectiveness is achieved by use of very large L/W1 . L/W1 = 20 – 25 appears to be maximum useful range in the absence of boundary-layer control. A few data are given where the inlet flow of the diffuser is distributed by obstructions. Recovery and effectiveness are found to be strongly dependent on type and amount of inlet turbulence.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):361-368. doi:10.1115/1.3658963.

An analytical and experimental study of flow in headers with a resistance parallel to the turbulent and incompressible main stream has been made. The purpose was to shape the inlet and exit headers, which had a large length-to-height ratio, so that the fluid would pass through the resistance uniformly. Analytical wall shapes and estimated total pressure drop through the headers were compared with experimental results. Good agreement between analysis and experiment was found for the cases compared.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):371-377. doi:10.1115/1.3658967.

An experimental study of the influence of tip clearance on the stall limits of compressor blades was conducted on a rectilinear cascade. By using the mirror and image technique the end wall boundary layer near the clearance was dispensed with. The blade loading was maximum at a distance from the tip clearance, but the clearance was found to relieve the pressure gradient in general and to retard stalling.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):379-383. doi:10.1115/1.3658971.

On the assumption that the motion of incipient cavitation bubbles on geometrically similar bodies is dynamically similar, the relation between incipient cavitation number kdi and Reynolds number Re has been obtained from the dynamical similarity law deduced from the equation of the motion of spherical bubbles. A comparison of calculated values based on this theory with experimental data obtained by R. W. Kermeen and others shows good agreement at values of Reynolds number greater than the critical Reynolds number. Also, by comparing this theory with the formula by R. T. Knapp, concerning scale effects on cavitation inception, it is shown that Knapp’s formula is a special case of the present theory.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):385-395. doi:10.1115/1.3658974.

Scale effects on cavitation are defined here as departures from the classical similarity relations when changing size, velocity, and/or properties of the fluid. The various phenomena governing such scale effects are examined and the resulting similarity laws, together with some expected scale effects, are tabulated. The theoretical expectations are then compared with extensive test data on desinent cavitation in cold water. This comparison leads to two different sets of plausible relationships for cavitation attached to a streamlined body, and cavitation not attached to a solid wall. However, the conclusions drawn are only tentative and qualitative, clearly indicating the need of further careful experimentation and analysis.

Topics: Cavitation , Water , Fluids
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):399-400. doi:10.1115/1.3658979.
Abstract
Topics: Fluids , Cavitation
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):401-406. doi:10.1115/1.3658980.

Scholz’s method for measurements on a two-dimensional cascade has been extended to include mass and energy input into the main flow by trailing-edge jets. Pressure recovery and mixing losses downstream of the cascade have been theoretically investigated and the need of low jet velocities has been emphasized. Improvements which can be expected by increasing the jet width but keeping the jet coefficient constant have been demonstrated. The airfoil tested was the NACA 65-(12)10 compressor blade with a thickened trailing edge. A stagger angle of 45 deg and a solidity of 0.915 were used throughout. Results are given in the form of wake profiles, axial and tangential force coefficients, and cascade polars.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):423-432. doi:10.1115/1.3658989.

An analytical method is presented for studying the compressible boundary-layer motion over a rotating disk including axial forced flow. Some existing incompressible flow data can be utilized. The range considered includes free-molecule flow, slip flow, and high-density gas flow. A new correlation for treating disk-friction data is suggested. General aspects of friction and heat transfer are discussed. Results suggest the rotating disk as a suitable tool for experimental study of mechanics of a rarefied gas.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):433-442. doi:10.1115/1.3658990.

The Scattergood Steam Power Plant of the City of Los Angeles uses Pacific Ocean water as a heat sink. During the design of the circulating water system which conveys the ocean cooling water to the condensers, it was necessary to predict the hydraulic behavior under certain unsteady conditions in order to establish design criteria. This article describes the circulating water system, the problems to be solved, the methods of mathematical analysis, and the analog computer solution of the resulting set of 28 simultaneous nonlinear differential equations.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):445-450. doi:10.1115/1.3658993.

Equations are developed to calculate speed and pressure transients of a hydraulic turbine during a load change. Water hammer, governor time, dashpot time, temporary speed droop, and promptness of governor response are taken into account. An example illustrates the application of equations to a step-by-step calculation.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):456-458. doi:10.1115/1.3659000.

Equations have been derived using rigid-water-column theory which permit rapid assessment of pressure surge magnitude owing to rejoinder of water columns in pump-discharge lines subsequent to a water-column separation induced by failure of power to the pump drivers. The method is valid only for systems which are equipped with check valves at the pumps.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):461-470. doi:10.1115/1.3659004.

The Magnus force on a rotating body traveling through a fluid is partly responsible for ballistic missile and rifle shell inaccuracies and dispersion and for the strange deviational behavior of such spherical missiles as golfballs and baseballs. A great deal of effort has been expended in attempts to predict the lift and drag forces as functions of the primary parameters, Reynolds number, ratio of peripheral to free-stream velocity, and geometry. The formulation and solution of the mathematical problem is of sufficient difficulty that experimental results give the only reliable information on the phenomenon. This paper summarizes some of the experimental results to date and the mathematical attacks that have been made on the problem.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(3):471-477. doi:10.1115/1.3659006.

A theory for the prediction of flow for fully choked divergent shroud nozzles has been compared with experiment and corrected empirically. The prediction of thrust has been extended to include both the underexpanded and overexpanded flow regimes in this type of nozzle. Comparisons with the theory have been made and good correlation found in both overexpanded and underexpanded regimes of flow.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Basic Eng. 1961;83(3):478-480. doi:10.1115/1.3659007.
Abstract
Topics: Whirls
Commentary by Dr. Valentin Fuster

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