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IN MEMORIAM

J. Fluids Eng. 1980;102(4):394-395. doi:10.1115/1.3240709.
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Abstract
Commentary by Dr. Valentin Fuster

EDITORIAL

J. Fluids Eng. 1980;102(4):396. doi:10.1115/1.3240710.
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Abstract
Commentary by Dr. Valentin Fuster

REPORTS

J. Fluids Eng. 1980;102(4):397. doi:10.1115/1.3240711.
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Abstract
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Fluids Eng. 1980;102(4):402-411. doi:10.1115/1.3240712.

An axial-flow research compressor facility, which is designed for relative flow measurement, is described in this paper. The facility has a rotating-probe traverse mechanism which is capable of traversing hot-wire, pilot and other probes at 0.09 deg intervals across the rotor blade passage. The data transmission system includes rotating transducers, pressure transfer device, ten-channel mercury slip-ring unit, scanivalve, etc. The instrumentation includes on-line data processing capability. A brief description of probes used as well as some typical data on the rotor blade static pressure, rotor endwall flow, and rotor wake characteristics are given in the paper.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):412-419. doi:10.1115/1.3240713.

Numerous results—most of them are published—have proved the applicability of the L2F-velocimeter to experimental studies of the complex compressor flow: e.g. the blade wakes and the shock-wave system within the blade passages. Furthermore, measurements close to the compressor surfaces provide information about boundary layers and flow separation. However, the measuring procedure is rather time-consuming. It takes about one hour to accumulate 10 to 15 vector measurements within a rotor blade channel. This paper presents a technique whereby the measuring time is reduced by a factor of ten. Mathematical considerations of the L2F-signal statistics lead to a modified calculation model and a new measuring procedure. Now, about 100 to 150 flow points can be acquired in one hour which includes the magnitude and direction of the mean flow vector as well as its turbulent components. This paper describes the innovations in optics, operational procedures, and electronics that have resulted in an enhanced state-of-the-art in flow measurement. Experimental results are also submitted and discussed.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):420-426. doi:10.1115/1.3240714.

The flow patterns in centrifugal pump impellers with three and seven blades, respectively, were measured using a cylindrical yaw probe and an oil surface flow method. The measured distributions of velocities and pressures for the seven (sufficient number) blade impeller at the design flow rate coincide well with the numerical solution obtained from the theoretical equation based on a potential flow. The flow patterns of the three (insufficient number) blade impeller deviate largely from those of the seven blade impeller both at the design and off-design conditions. The values of the slip factor deduced from the data of velocity measurements in the impeller passage were compared with those calculated by commonly-used formulae, and considerably good agreement was obtained for the seven blade impeller.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):427-432. doi:10.1115/1.3240715.

In order to assist in the understanding of high speed flutter, a series of tests has been conducted on a research fan in which the blade surface pressures have been measured by means of miniature silicon diaphragm pressure transducers embedded in selected fan blades. Prior to this investigation a program of rig tests was conducted to examine the effects of centrifugal force and vibration on the transducer performance and a transducer mounting technique was developed to minimize blade induced stress in the transducer. Instantaneous measurements of the tip stagger angles of the pressure instrumented fan blades have enabled a cross correlation to be performed on the blade surface pressure data and the blade tip angles. Some typical test results are shown.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):433-438. doi:10.1115/1.3240716.

The behavior of supercavitation as well as of cavitation, especially near the separation point, were carefully observed in a two-dimensional subcritical flow around a cylinder with and without ventilation. Since supercavitating flow generally detaches from the separation point abruptly, the assumption “smooth separation” often applied is evidently unsatisfactory. There is a transient region, where a kind of supercavitation and of subcavitation can be alternately observed. Outside the immediate neighborhood of the separation point, the flow features are uniquely expressed by σc based on cavity pressure both with and without ventilation, while within that neighborhood, there arise some different features due to ventilation.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):441-445. doi:10.1115/1.3240720.

A criterion for the onset of a slug flow in a horizontal duct is derived theoretically. A potential flow analysis is carried out by considering waves of finite amplitude. The stability criterion is obtained by introducing the wave deformation limit and the “most dangerous wave” concept in the stability analysis. The present theoretical criterion for slug formation shows very good agreement with a large number of experimental data and with some empirical correlations.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):446-453. doi:10.1115/1.3240721.

Equations of motion for air bubbles in a centrifugal pump impeller were obtained and solved numerically for a flow in a radial-flow-type impeller, and the results were compared with experiments. Governing factors for the bubble motion are the force due to the pressure gradient, the drag force due to the flow resistance of the surrounding liquid, and the inertia force due to virtual mass of the liquid. If the bubble diameter is reduced continuously, the effect of the inertia force is also reduced and trajectories of the air bubbles approach more and more to the path of the flowing water.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):456-461. doi:10.1115/1.3240725.

A parabolic numerical analysis procedure has been used to predict the flow in a straight, radial rotating channel of rectangular cross-section, chosen as a simple model of an impeller passage. A two equation turbulence model was employed, with alternative modifications, to include the influence of Coriolis force on turbulent kinetic energy. Alternative Coriolis force terms were evaluated by comparisons in a high-aspect-ratio duct with measured velocity, wall shear stress and turbulent viscosity. Secondary velocity predictions were checked with data from a low-aspect-ratio duct where the Coriolis modification of turbulence was found less influential than the secondary flow in the modification of side wall shear stress.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):462-472. doi:10.1115/1.3240726.

The wakes of turbomachinery rotor blades are turbulent, three-dimensional, and are subjected to curvature and rotation effects. The objective of this study is to predict the development of such wakes and compare the predictions with the existing data. A finite difference procedure is employed in the numerical analysis of the wake utilizing the continuity, momentum, and turbulence closure equations in the rotating curvilinear and non-orthogonal coordinate system. The turbulence closure is affected by the modified Reynolds stress model. The effects of curvature and rotation on the turbulence structure are accounted for with this turbulence closure model. The pedictions from the present turbulence model agree well with the mean velocity and the turbulence wake data.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):473-477. doi:10.1115/1.3240727.

Theoretical and experimental results concerning rotational inviscid flow in an annulus, pipe or channel of variable cross-section are given. Vorticity and continuity considerations are used to determine the velocity profile downstream from the variable area portion in terms of the velocity profile upstream. The lengthening or shortening of vortex lines alters the vorticity in the flow. Regimes of possible reverse flow and flow separation are obtained. The agreement between the theory and experiment is good.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):478-480. doi:10.1115/1.3240728.

Measurements of three orthogonal components of mean velocity and the rms values of the corresponding velocity fluctuations have been obtained by laser-Doppler anemometry in the axisymmetric swirling flow in a motored piston-cylinder assembly. The crank was rotated at 200 rpm and the inlet arrangement, a simulated open valve inclined at 60 deg to the cylinder head, provided swirl numbers at entry of approximately 0.45 and 1.20. There was no significant compression. The present results and previous results without swirl are compared.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):481-485. doi:10.1115/1.3240729.

This study focused on two aspects of the cavitation damage problem, namely an energy approach to the scaling of cavitation damage in the incubation zone and damage near the leading edge of a test model. The damage to the surface of the models was in the form of small indentations in which no material was removed. For a wide range of velocities namely 14.9 to 59.3 m/s the rate of pit formation per unit area in the maximum damage zone increased by the sixth power of velocity. Furthermore it is shown that the damage rate versus velocity data are in good agreement with three other investigations. The volumes of the pits were found to increase by the fifth power of velocity. A relationship between the volume of a pit and the cavitation bubble collapse energy absorbed was developed. The damage to the leading edge was felt to be due to the reentrant jet striking the leading edge of the cavity creating a short term pressure rise causing the collapse of any cavitation bubbles in this area.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):486-493. doi:10.1115/1.3240730.

An experimental investigation to improve the stage efficiency through the use of vaned diffusers is presented. Sixteen different vaned diffusers were tested on a model compressor rig. The results showed that the pressure recovery of the vaned diffuser increased up to the critical diffusion ratio, which was shown to be approximately 0.5. The measured pressure distribution around vanes of the well-designed diffusers which had the fair diffusion ratios, were found to agree well with the potential flow solutions. Finally, the importance of the diffuser inlet configuration to the improvement of the stage efficiency is discussed.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):494-496. doi:10.1115/1.3240731.

The flow over a blunt plate aligned parallel to the stream was visualized using dye tracers. A leading edge separation bubble was observed to form at a Reynolds number based on plate thickness of 100. The steady, laminar separation bubble on a long plate, L/t ≥ 8, grows in size with increasing Reynolds number reaching a maximum streamwise length at Ret = 325. The separated shear layer becomes unsteady and the bubble shrinks in size with further increases in Reynolds number. The leading and trailing edge separation zones on short plates, L/t ≤ 4, may combine to form a large recirculation pocket.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):499-501. doi:10.1115/1.3240733.

A new technique is proposed for measuring very low pressure differences between two points in a fluid. The device combines an optical velocity measurement with the Hagen-Poiseuille relation to infer the pressure drop. A prototype model has been constructed which measures pressure differences in the range 3.07×10−5 to 1.59×10−3 cm H2 O. The estimated uncertainty of this technique is approximately 4 percent. However, no accurate, independent calibration of this device has yet been achieved.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):502-509. doi:10.1115/1.3240734.

The problem of the propagation of three-dimensional laminar instabilities, due to crossflow, in a three-dimensional compressible boundary layer, is examined using linear theory. The theory is applied to the case of a transonic swept wing. It is shown that compressibility has a mild stabilizing effect in the regions where the crossflow is strong. The problem of defining the direction of propagation of the disturbances is discussed.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):510-518. doi:10.1115/1.3240735.

There are many applications in industrial fluid mechanics and fluidic technology where jets of fluid interact. This paper examines the interaction of two liquid laminar free jets under low Reynolds number conditions and particularly highlights the phenomenon of the inwards deflecting jet. A potential flow solution is developed for the modelling of the control jet flow in the vicinity of the control nozzle exit plane, which demonstrates the presence of a net suction force modifying the momentum interaction of the two orthogonal jets under these low Reynolds number conditions.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J. Fluids Eng. 1980;102(4):525. doi:10.1115/1.3240750.
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Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1980;102(4):526. doi:10.1115/1.3240752.
FREE TO VIEW
Abstract
Topics: Fluid dynamics
Commentary by Dr. Valentin Fuster

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