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EDITORIAL

J. Fluids Eng. 1976;98(4):589. doi:10.1115/1.3448422.
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Abstract
Commentary by Dr. Valentin Fuster

COMMENTARY

J. Fluids Eng. 1976;98(4):590-591. doi:10.1115/1.3448423.
Abstract
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Fluids Eng. 1976;98(4):592-606. doi:10.1115/1.3448424.

Progress achieved in numerical analysis during the past decade now permits the turbo-machinery designer to carry out a wide variety of inviscid, steady flow, two-dimensional calculations for compressible sybsonic and transonic flow fields, including some strongly diffusing flows. Three-dimensional (including viscosity) calculations are under development and should find wide spread use as analysis tools during the next decade. This review offers an introduction to recent advances in numerical turbomachinery design methods guided by the author’s design usage of several of the techniques reported.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):607-613. doi:10.1115/1.3448425.
Abstract
Topics: Engineers
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):614-618. doi:10.1115/1.3448426.

This paper concerns the pressure losses involved in measuring flow rate. These losses can be large and affect the choice of pump or flow metering section to be used. Solutions are developed for predicting these losses for various fluid meter arrangements. Several methods are described for reducing fluid meter loss, including the use of a new step diffuser. Experimental results are given which verify the theoretical solutions. Design curves are presented to aid in the optimum choice of the flow metering section.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):619-625. doi:10.1115/1.3448427.

Fuel pumps and metering systems are becoming more complex and expensive to meet the high performance requirements of advanced gas turbine engines. A simple, inlet throttled, centrifugal pump integrated with a retracting vane starting element provides the potential for a reliable, high performance design capable of reducing the cost, weight, and temperature rise of the fuel system. This paper presents the results of recent efforts to develop the retracting vane element and to integrate it with a vapor core centrifugal pump in order to meet the fuel performance and functional requirements of an advanced gas turbine main fuel pump.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):626-632. doi:10.1115/1.3448430.

Measurements are given for the combined effects of a change of surface roughness and a simultaneous change of pressure gradient. The latter is negative in a fully developed turbulent, two-dimensional smooth channel flow upstream of the discontinuity, but is artificially held to a value of zero in the rough channel following the surface discontinuity. Measurements of mean velocity, turbulent intensity, and wall shear stress in the current zero pressure gradient apparatus are compared with similar measurements made in the same apparatus with a negative pressure gradient in the rough channel. Results indicate that removal of the pressure gradient in the rough channel does not affect the growth rate of the internal boundary layer nor that of the sublayer; nor does the modified pressure gradient greatly reduce the transitional overshoot of wall shear stress and turbulence intensity previously observed.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):635-643. doi:10.1115/1.3448434.

The flow resistance in a plate roughened by equally spaced wires at right angles to the flow direction was investigated experimentally by measuring the turbulent boundary layer developing along it. Measurements of pressure distribution around a roughness element revealed that the pressure drag accounts for a large portion of the surface resistance and remaining skin frictional part is almost equal to that of a smooth plate. Measurements were also made for plates having three-dimensional roughness. These plates were roughened by short wires in a staggered manner. In this case, the boundary layer was found to have a three-dimensional structure due to accompanying secondary currents.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):645-652. doi:10.1115/1.3448437.

A hydraulic gas compressor has no moving parts and compresses gas at the expense of hydraulic energy by means of entrainment in a downward moving column of liquid with subsequent separation of gas and liquid at depth. Documentation is cited giving the history and performance data for large hydraulic air compressors built around 1900. An analysis is presented based on one-dimensional bulk parameter modeling of the flow, which enables computerized calculation of the performance of hydraulic gas compressors. The results of small-scale experiments are presented showing agreement with analytical results. It is further shown that the analytical results agree with reported performance data for old large-scale compressors. Unique capabilities of the compressor for transducing and transforming energy are described and application studies are suggested in several areas. Calculated results are presented as an example, for the design and performance of a large air compressor, showing the effect on performance of varying the applied hydraulic head.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):654-665. doi:10.1115/1.3448441.

Flow distribution in the lateral branches of dividing, combining, reverse, and parallel flow manifold systems is studied both analytically and experimentally. Predictions for the flow rates and pressures in the headers of any of the above four basic manifold configurations are obtained from the solution of two first order differential equations involving the flow rate and the pressure difference across headers (pressure-flow equation set), or by the solution of a second order, nonlinear ordinary differential equation involving the flow rate alone (flow distribution equation). Experimental results are presented for various manifold designs having different lateral/header area ratios, lateral flow resistances, and length/diameter ratios. Good agreement is obtained between the analytical and experimental results. Dimensionless parameters which affect flow distribution are identified and discussed with respect to the generalized coefficients of the analytical model. The present method of analysis is proposed for general application in evaluating the performance of flow distribution systems.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):667-672. doi:10.1115/1.3448444.

A semianalytical prediction of the trajectory of a turbulent jet issuing at various angles to the horizontal into a crossflowing stream is presented. The predictive technique utilizes the basic conservation equations, in conjunction with idealizations instigated by experimentally observed jet behavior, to arrive at two-dimensional trajectories in either a uniform or a spatially variable mainstream crossflow. Comparisons of the predictions with available experimental data yield good agreement over a range of jet to crossflow velocity ratios of two to eighteen.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):674-679. doi:10.1115/1.3448447.

Severe vibration problems were encountered during initial operation of large Deriaz pumps. This paper describes those problems, the alternative solutions available, and the corrective action taken. Transient shaft vibrations prevented normal pump shutdown operation, when severe counter-rotational whirl occurred as the shaft speed decreased. Vibration at low blade angles preclude operation below half the rated flow. High intake water levels led to rotational shaft whirl in the normal operating range. Subsequent field testing evaluated various possible sources of vibration excitation, and verified the remedy of air injection into the headcover.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):681-687. doi:10.1115/1.3448452.

Cavitation characteristics were determined for sharp-edged orifices. Both circular and rectangular orifices were studied. A simple model is proposed, which was experimentally verified over a range in back pressure, L/d, and entrance radius. Sharp-edge orifices were then incorporated into unlike-impinging-doublet injector elements. The spray mixing uniformity was determined at cavitated and noncavitated conditions. Cavitation was shown to result in a substantial reduction in mixing uniformity for circular orifice elements. Over an identical range in experimental conditions, the rectangular orifice element did not experience lowered mixing uniformity. The orifice cavitation and mixing results should find use in a wide range of applications.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):688-692. doi:10.1115/1.3448453.

The onset of the stable laminar secondary flow (hygrocysts) that arises when a partially filled container is rotated about a horizontal axis has been experimentally studied. Nearly 500 sets of data on thirteen fluid systems were obtained and analyzed using a multiple linear regression computer program. Numerous dimensionless correlation models were investigated, the best being a power law relationship between the Reynolds number, volume fraction, and Weber number. Anomalous behavior was observed in that as the volume fraction approached unity, the critical speed of the onset of the secondary flow approached zero, indicating non-rigid body motion (driven by the lateral body force) in completely filled horizontal rotating containers.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):695-700. doi:10.1115/1.3448458.

Turbulent boundary layers experiencing a time mean adverse pressure gradient and a controllable periodic oscillation are examined experimentally over a tenfold range of dimensionless frequencies, and amplitudes less than ten percent of the lime mean diffuser inlet velocity, for well defined diffuser inlet conditions. Organized velocity fluctuations of the diffuser core and boundary layer flow fields, along with organized wall pressure fluctuations, are characterized using a phase averaging process. Amplitudes of the core velocity fluctuations and wall pressure fluctuations decay in the streamwise direction. Depending on the dimensionless excitation frequency, the amplitude of the organized velocity fluctuations in the boundary layer can exceed the local core flow amplitude by as much as an order of magnitude. At relatively low dimensionless excitation frequency, the organized velocity fluctuation amplitude distribution within the boundary layer grows in an orderly fashion with streamwise distance, and the phase of these fluctuations consistently leads the local core flow fluctuation. At relatively high dimensionless excitation frequency, phase lags of the velocity fluctuations within the boundary layer, relative to the local core flow fluctuation, can extend across the entire boundary layer. Over the range of frequencies examined, the mean flow field of the diffuser remained essentially unaltered.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):702-706. doi:10.1115/1.3448462.

An analytical method is presented for solving the governing equation for fully developed, steady, incompressible laminar flow through ducts of constant cross-section having a complex geometry. The technique uses the Schwarz-Neumann alternating method along with least squares point matching. The method is applied to a complex shaped duct and the resulting velocity series solution is used to calculate the flow rate and pressure drop (f•Re) for a range of duct sizes. Numerical results are presented and compared with experimentally determined friction factors for a duct of similar geometry.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):707-713. doi:10.1115/1.3448463.

This paper describes a secondary streaming motion that appears during the pulsatile flow of a viscous, incompressible fluid through rigid circular channels having walls which diverge at a slow exponential rate. Arising primarily from the interaction of viscous effects with convected inertial effects, this steady streaming motion acts to continuously retard downstream flow near the wall surface and enhance such flow nearer midstream. The secondary flow phenomenon is shown to be directly proportional to mean Reynolds Number, inversely proportional to the unsteadiness parameter of the flow, and to attenuate with decreasing rates of channel divergence. These effects are all self-consistent and interdependent.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):715-722. doi:10.1115/1.3448466.

Vertically downward slug flow of air-water mixtures was experimentally investigated in circular pipes of diameter D = 2.60, 10.16, and 14.0 cm. The terminal velocity of descending, stationary, and ascending bubbles in downward flows was measured and correlated with the air and water volumetric flux densities. Except for very small pipe diameters, bubbles in downward flow are unstable and eccentrically located off the pipe axis in regions of lower fluid velocities. Consequently, the value of the flow distribution parameter C0 is less than unity for downward flow, compared to C0 = 1 for rising bubbles in quiescent liquid, and C0 = 1.2 for ascending bubbles in upward flow. Above a certain pipe diameter stable Taylor bubbles are not possible for downward flows. The terminal velocity coefficient C1 is no longer 0.35 for downward flows in relatively large pipes because the unstable bubbles ride the pipe wall, resulting in a higher value of C1 .

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):723-726. doi:10.1115/1.3448467.

An expression for the wake deficit g(Π, y/δ) in a turbulent boundary layer is combined with a function f(U+ ) for the inner layer to yield a single formula for the complete velocity profile in the form y+ exp {Kg(Π, y/δ)} = f(U+ ). Close agreement is shown with data from boundary layers in a wide range of pressure gradients and beneath a turbulent free stream. The formula will be particularly useful for integral and differential calculation methods.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):728-735. doi:10.1115/1.3448470.

Flow control techniques in wide-angled conical diffusers are discussed. Selected performance characteristics of a wide-angled conical diffuser and tailpipe with and without a star flow-control device are also presented. The diffuser performance is sensitive to the star location and geometry and to the diffuser inlet flow conditions. The correct combination of the first two factors for a given inlet condition leads to a significant increase in pressure recovery and flow stability in the diffuser and tailpipe, together with satisfactory mean velocity profiles for entry to downstream duct components.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):736-739. doi:10.1115/1.3448471.

The response of a single inclined rotating hot wire anemometer was analyzed. The mean flow anemometer response equation was expanded in a Fourier Series about the fundamental frequency of rotation. Utilizing the d-c level and the first two harmonics of the response it is possible to construct the mean flow velocity vector within a solid angle determined by the mounting angle of the wire. The rotating anemometer response was measured using the technique of two phase lock-in detection to determine the first two harmonics and their phases relative to the fundamental frequency of rotation. Determination of the mean flow velocity vector using this technique was found to be feasible.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):740-748. doi:10.1115/1.3448472.

The High Speed and Free Surface Water Tunnels are the principal research facilities of the Hydrodynamics Laboratory at the California Institute of Technology. Significant changes have been made to these facilities since their erection in 1945. This paper presents a description of these facilities, and their operating characteristics, as they exist today. Recent projects, new instrumentation, and support facilities are also described.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):749-752. doi:10.1115/1.3448473.

The circuit and application of an inexpensive simple linearized hot wire anemometer especially suited to turbulence research in incompressible media is described. Special features of the design are very high stability, simple bridge adjustment, and a linearizer having an adjustable exponent and very high transfer function accuracy. Measured frequency response is in excess of 100 kilohertz for the bridge and 7.5 kilohertz for the linearizer.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):753-758. doi:10.1115/1.3448474.

Numerical predictions are presented of fully-developed turbulent flow through a concentric annulus in which the core tube rotates about its axis. Comparisons are drawn with the extensive experimental data of Kuzay and Scott [1] which span Reynolds numbers from 1.7 to 104 to 6.5 × 104 and with rotational speeds of the core tube varying from zero to nearly 2.8 times the bulk axial velocity. Predictions have been obtained by means of an adapted version of the Patankar-Spalding [5], numerical procedure employing, as turbulent transport model, the version of the mixing length hypothesis applied by Koosinlin, Sharma and Launder [2] to flows on spinning cones and cylinders. Agreement with experiment is generally close at the higher relative swirl rates but the predictions of the swirling velocity profile deteriorate as the bulk flow rate is increased. The discrepancy seems to be due to the experimental data requiring a greater development length as the magnitude of the rotational velocity is reduced relative to that of the mean flow. Demonstrative developing-flow predictions are provided which exhibit closer agreement with the experimental data.

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

TECHNICAL BRIEFS

J. Fluids Eng. 1976;98(4):762-764. doi:10.1115/1.3448476.
Abstract
Topics: Reynolds number
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):764-766. doi:10.1115/1.3448477.
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):766-768. doi:10.1115/1.3448478.
Abstract
Topics: Turbulence , Annulus
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):770-771. doi:10.1115/1.3448480.
Abstract
Topics: Vorticity , Equations
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):771-773. doi:10.1115/1.3448481.

When a circular cylinder is placed in a two-dimensional shear flow, a lift force is experienced by the cylinder. In the case of hot-wire measurements in the viscous sublayer, this will give rise to a displacement of the wire from its true position. The resultant measurements are found to be in error if the wire length to diameter ratio is > 300 and the shear gradient of the flow is large.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1976;98(4):773-775. doi:10.1115/1.3448482.
Abstract
Commentary by Dr. Valentin Fuster

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