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EDITORIAL

J. Fluids Eng. 1975;97(2):141. doi:10.1115/1.3447234.
FREE TO VIEW
Abstract
Topics: Uncertainty
Commentary by Dr. Valentin Fuster

REPORTS

J. Fluids Eng. 1975;97(2):142. doi:10.1115/1.3447235.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

COMMENTARY

J. Fluids Eng. 1975;97(2):143. doi:10.1115/1.3447236.
Abstract
Topics: Unsteady flow
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Fluids Eng. 1975;97(2):146-154. doi:10.1115/1.3447237.

“Complex” turbulent flows are those which cannot be predicted with acceptable accuracy by methods developed in classical thin shear layers. This is a subjective and time-dependent definition but even at its narrowest it includes a large class of engineering and environmental flows. Examples include shear layers which interact, in pairs or larger numbers, and shear layers which have been perturbed by body forces, such as buoyancy, or extra rates of strain such as longitudinal curvature or lateral divergence. This review assesses our current knowledge of complex turbulent flows and our ability to predict them. It also assesses the usefulness of the boundary layer approximation in engineering flows and suggests methods of extending it.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):155-160. doi:10.1115/1.3447238.

A unique vortex nozzle facility has been conceived and developed to simulate the exit flow from a high pressure ratio centrifugal compressor impeller. Visual studies and performance measurements have been made for three vane sets representing common designs for vaned radial diffusers. Motion pictures show the progression from choke through operating to surge conditions as the back pressure on the diffuser is increased. The films, together with total and static pressure measurements, indicate that surge is an instability triggered by flow separation in the vaneless or quasivaneless space ahead of the diffuser throat. A geometrical criterion for the onset of surge is identified. The surge-to-choke operating range of the three diffusers appears to be a function of the number of diffuser vanes only.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):174-179. doi:10.1115/1.3447249.

Results are displayed which show the effect of gas specific heat ratio, impeller tip running clearance, and compressor insulation on modeling of a high-pressure-ratio compressor’s performance. The data were obtained using a low-speed-of-sound gas and a compressor previously tested extensively in air. Duplication of the air inlet specific heat ratio was found to be essential to modeling the air-equivalent flow rate accurately. Stage pressure ratio and stage efficiency were found to be less sensitive to the accurate replication of the air specific heat ratio. For the compressor tested, stage isentropic efficiency increased as impeller-to-shroud tip running clearance was reduced from 15 to 5 percent of the impeller tip axial depth. The measured stage efficiency was found to depend strongly on the heat transfer between the compressor and surroundings.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):180-190. doi:10.1115/1.3447250.

It was proved experimentally that the conditions of cavitation incipience, such as the positions of incipient cavitation bubble formation and collapse, extent of cavitation, and the propensity toward cavitation onset (in terms of cavitation coefficient or of flow velocity at cavitation incipience), are affected by the degree of turbulence present in the free stream. A side experiment was also undertaken to ascertain the validity of the use of a sphere in measuring the degree of turbulence.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):191-196. doi:10.1115/1.3447251.

An hydraulic ram is a pump in which the momentum of a driving stream of water undergoing a small head drop is used to pump a small portion of the stream to a head considerably greater than that of the supply. An attempt has been made to identify the features of the ram; the drive head and flow, the discharge (or pump) head and flow, the cycle frequency, and the system efficiency. Analytical results are expressed in terms of the ratio of the maximum drive velocity at drive valve closure to the maximum steady state velocity with the drive valve wide open. This ratio is always less than one. Comparison of the analysis with experimental results gives a numerical correlation of heads and flows. The cycle frequency and system efficiency are not predicted with great accuracy, but the trends are predicted correctly.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):197-210. doi:10.1115/1.3447252.

An analytical and experimental investigation of the characteristics of a three-dimensional turbulent boundary layer in a rotating helical channel is reported in this paper. Expressions are developed for the velocity profiles in the inner layer, where the viscous effects dominate, and the outer layer, where the viscous effects are small. The prediction of boundary layer growth is based on the momentum integral technique. The analysis is valid for incompressible flow through a rotor blade row with small camber. The velocity profiles, wall shear stress and limiting streamline angles are measured inside the passages of a flat plate inducer at various radial and chordwise locations using rotating probes. The measurements are in general agreement with the predictions. Flow near the blade tip is found to be highly complex due to interaction of blade boundary layers and the annulus wall, resulting in appreciable radial inward flow as well as a defect in mainstream velocity near the midpassage. A wall shear stress correlation, which includes the effect of both Reynolds number and rotation parameter, is derived from the measured data.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):211-216. doi:10.1115/1.3447253.

The virtual mass effect of a liquid annulus surrounding a shell is established in closed form. Simple support conditions for the shell and open end conditions for the liquid annulus are considered. In this fashion one arrives at a generalization of Stokes’ formula which treats the case when a rigid rod moves back and forth in the liquid. The present theory encompasses vibrations of the beam mode and breathing mode types. Availability of the entrained liquid mass expression is of importance in the computation of reactor and missile vibrations. The results for the beam modes of shell vibrations, for the example considered, are in satisfactory agreement with previous results obtained on the basis of beam analysis.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):217-224. doi:10.1115/1.3447254.

Theoretical predictions of turbulent boundary layer development under the influence of strong favorable pressure gradients made using a finite-difference calculation procedure are compared to experimental data. Comparisons are presented for low speed flows with and without wall heat transfer as well as for supersonic flows with adiabatic walls. The turbulence model used is governed by an integral form of the turbulence kinetic energy equation and the results are compared with predictions made using a conventional equilibrium turbulence model based upon Prandtl’s mixing length, a Clauser-type eddy viscosity model used by Cebecci and Mosinskis, and a two-equation turbulence energy model of Launder and Jones.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):225-233. doi:10.1115/1.3447255.

Design charts for wind tunnel contractions are developed using an inviscid, incompressible flow analysis. A contour formed of two cubic arcs joined smoothly together was found to be a good choice for a wall shape. Therefore, it was selected as the basis for a one-parameter family of wall shapes, which was then investigated in detail. The design chart parameters are the maximum wall pressure coefficients at the inlet (as an indicator of the danger of separation at the inlet end) and at the exit (which is related to the exit velocity nonuniformity). For any choice of these two parameters the charts yield the shape parameter and the nozzle length for this particular family of shapes. The charts may be used to design nozzles with no local separation at the inlet, and with any desired exit velocity uniformity. When the two pressure coefficients are chosen so that separation at both ends is just avoided, the exit boundary layer thickness should be near its minimum.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):234-241. doi:10.1115/1.3447256.

A simple turbulent energy model, based on an improved version of Wolfshtein’s model for Newtonian flows, with a variable damping parameter, is used to describe the effect of linear polymers on the velocity profile and the turbulent energy distribution in channel and pipe flows. Measured mean velocity profiles seem to be in good agreement with the model, which predicts as well the observed increase in turbulent energy near the wall in flows with drag reduction.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Fluids Eng. 1975;97(2):242-243. doi:10.1115/1.3447257.
Abstract
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):243-246. doi:10.1115/1.3447258.
Abstract
Topics: Pipes
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):246-247. doi:10.1115/1.3447259.
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):247-249. doi:10.1115/1.3447260.
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):252-253. doi:10.1115/1.3447262.
Abstract
Topics: Diffusers
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):253-256. doi:10.1115/1.3447263.

If the exact metric influence of curvature is retained and the displacement effect neglected, it can be shown that the momentum integral for two-dimensional, curved boundary-layer flows is identical to the von Karman momentum integral. As a result, attempts by previous researchers to account for longitudinal curvature effects by adding more terms to the momentum integral are shown to be correct.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):256-258. doi:10.1115/1.3447264.

A new analytical method is presented, allowing direct, easy and accurate computation of the nonlinear waterlevel oscillations occurring in a simple surge tank under instantaneous load rejection. The method yields several design equations and is also applicable in the case of instantaneous load demand and to other types of surge tanks.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):258-260. doi:10.1115/1.3447265.
Abstract
Topics: Suction , Diffusers
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(2):260-262. doi:10.1115/1.3447266.

The steady-state form of a plane waterhammer wave is considered in order to illustrate the application of perturbation methods to fluid transients. An asymptotic solution is obtained for small Mach numbers. The jump conditions are determined and a solution for the internal, viscous structure of the wave is found.

Commentary by Dr. Valentin Fuster

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