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EDITORIAL

J. Fluids Eng. 1974;96(4):309. doi:10.1115/1.3447161.
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Abstract
Commentary by Dr. Valentin Fuster

REPORTS

J. Fluids Eng. 1974;96(4):310. doi:10.1115/1.3447162.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Fluids Eng. 1974;96(4):311-316. doi:10.1115/1.3447163.

The apparatus of previous workers are described in order to evaluate the need for further studies of mass transfer into turbulent boundary layers. The apparatus built at the University of Waterloo is then described with particular reference to the areas where it is felt that significant improvement has been achieved over other apparatus. Some suction data obtained on the present apparatus is presented.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):317-322. doi:10.1115/1.3447164.

The von Karman vortex streets formed in the wakes of vibrating, flexible cables were studied using a hot-wire anemometer. All the experiments took place in the flow regime where the vibration and vortex-shedding frequencies lock together, or synchronize, to control the wake formation. Detailed measurements were made of the vortex formation flow for Reynolds numbers between 230 and 650. As in the case of vibrating cylinders, the formation-region length is dependent on a shedding parameter St* related to the natural Strouhal number and the vibrational conditions. Furthermore, the near wake configuration is found to be dependent on the local amplitude of vibration suggesting that the vibrating cylinder rseults are directly applicable in that region.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):323-332. doi:10.1115/1.3447165.

This paper investigates the feasibility of diagnosing intraurethral obstructions in males by means of a pressure pulse technique. Initial discussion centers on some of the anatomical and physiological characteristics of the male lower urinary tract for both normal and abnormal (obstructed) conditions. Present methods of diagnosis are reviewed and the limitations of these techniques are discussed. An alternate method of diagnosis is then described which is based on examination of wave reflection behavior in the urethra during micturition after a pressure pulse is generated by means of quick-acting valve downstream of the meatus. Numerical results based on a proposed analytical model show that reflected waves from upstream obstructions can be detected, even for partial valve closure, and that induced peak pressures can be maintained within acceptable physiological limits. These results imply that the technique should be useful as a means of diagnosing obstructions in the male lower urinary tract.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):333-340. doi:10.1115/1.3447166.

The boundary layer simplification of the Navier-Stokes equations for hydrodynamically developing laminar flow with constant physical properties in the entrance region of concentric annuli with rotating inner walls have been numerically solved using a simple linearized finite-difference scheme. Additional results to those existing in the literature by Martin and Payne [1–2] will be presented here. An advantage of the analysis used in this paper is that it does not solve for the stream function and vorticity, but predicts the development of tangential, axial and radial velocity profiles directly, thus avoiding numerical differentiation. Results for the development of these velocity profiles, pressure drop and friction factor are presented for five annuli radii ratios (0.3, 0.5, 0.674, 0.727 and 0.90) at various values of the parameter Re2 /Ta. The paper may be considered as a direct comparison between the boundary layer solution and the complete solution of the Navier-Stokes equations [1–2] for that special case.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):341-347. doi:10.1115/1.3447167.

Hydrostatic thrust bearings commonly employ a sharp-edged asymmetric inlet, generally referred to as an inherent restrictor. For gas and liquid metal bearings, this inlet configuration offers significant advantages and is of definite practical interest. In this paper, an approximate solution is obtained for the laminar flow past the sharp-edged asymmetric inlet to a channel flow or a bearing film, using a simple integral method. The results exhibit important features of the oblique flow disturbance associated with inherent restrictors, including the occurrence of a separation bubble highly destabilizing to laminar flow. From this solution, a first approximation to the inlet pressure loss generated by the separation-induced local breakdown of laminar flow is calculated through the use of energy and momentum theorems. The predicted Reynolds number dependent pressure loss coefficient shows substantial agreement with available experimental data.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):348-352. doi:10.1115/1.3447168.

An existing integral boundary layer calculation procedure is modified to predict turbulent boundary layers developing in a turbulent freestream. Extra terms in both the turbulence model equation and the momentum integral equation are introduced to account for the effects of freestream turbulence. Good agreement with flat plate boundary layer measurements in a turbulent freestream has been obtained, while comparison with measurements in a severe adverse pressure gradient shows qualitative agreement with experiments.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):353-357. doi:10.1115/1.3447169.

Experiments were performed to examine the resistance law for non-Darcy compressible gas flow through a porous material. A particular objective of the investigation was to determine whether a resistance law deduced from incompressible flow experiments could be applied to flows with significant density changes. To this end, the coefficients appearing in the Forchheimer resistance law were first determined from experiments in the incompressible flow regime. These values were then used in an analytical model employing the Forchheimer resistance law to predict streamwise pressure distributions for subsonic compressible flow through the porous material. Corresponding experimental pressure distributions were measured for flow Reynolds numbers up to 81.6. At the highest Reynolds number of the tests the density changed by about a factor of two along the length of the porous medium. The greatest discrepancy between experimental and predicted pressures at any Reynolds number was 2 percent. This agreement lends strong support to the validity of using the incompressible Forchheimer resistance law for subsonic flows in which density changes are significant.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):358-364. doi:10.1115/1.3447170.

This paper discusses the appropriate scaling factors for the modeling of the fluid-mechanical interaction of complex structures. The possible mechanisms of flow-excited vibration are described, and scaling parameters are derived from considerations of the mechanical and fluid systems. The paper is particularly concerned with the flow-induced vibrations of banks of cylinders in single phase, high Reynolds number, turbulent, cross flow, as occur for example in light water nuclear reactors and heat exchangers. It is concluded that the modeling of the tube banks in light water nuclear reactors will involve a mismatch of Reynolds number, but that the major phenomena of fluid-solid interaction in the single-phase flow region will probably be closely replicated if the Reynolds number is high enough so that the entering flow is turbulent and if the scaling ratio is not too large.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):365-369. doi:10.1115/1.3447171.

A single boundary layer model to account for transient viscous effects is applied to small amplitude sinusoidally disturbed turbulent flow in a tube. The viscous dissipation is calculated using a transfer function relating the local boundary layer velocity gradient to the core velocity. A simple expression for the attenuation factor is derived and the analytical results are shown to be in excellent agreement with previously reported experimental data.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):370-376. doi:10.1115/1.3447172.

Automatic control of an oil well drilling process requires the knowledge of the dynamics of signal propagation through the annulus formed between the drill and the casing. This paper extends work previously done for circular lines to the annular case. Attenuation and phase speed are presented for various radius ratios as a function of signal frequency. For the liquid case, the results are correlated through the use of an equivalent radius.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):377-383. doi:10.1115/1.3447173.

The small signal frequency response of rigid pneumatic transmission lines of annular cross section has been obtained. Dimensionless expressions for the velocity and temperature profiles are obtained by solving the unsteady continuity, momentum, and energy equations for the boundary conditions of isothermal walls and no-slip flow at the walls. As a consequence, shear flow effects are included. By electric-pneumatic analogy the series impedance and shunt admittance per unit length of line are obtained and used to find the characteristic impedance and propagation operator. These quantities are shown to be dependent on both the signal frequency and the radius ratio of the annular cross-section. The annular line results are compared with previously obtained results for circular and rectangular lines.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):384-388. doi:10.1115/1.3447174.

The transition process of laminar flow between parallel plates is investigated experimentally. This problem has recently gained much attention with several reported works; however, the maximum transition Reynolds number reported has been approximately 3000 (based on average velocity and channel height) whereas the theoretical critical Reynolds number is 7700. Primary emphasis in this work is on approaching the theoretical limit in an experimental facility. A high aspect ratio (70 to 1) channel was used with air as the fluid. As the disturbance level at the entrance to the parallel plate section was reduced the transition Reynolds number increased monotonically. At a disturbance level of 0.3 percent the transition Reynolds number was 6700. Near transition small nearly sinusoidal waves in the critical shear layer were observed. The frequency of the waves was approximately 70 hertz, close to the frequency associated with the Tollmien-Schlichting waves of the critical point of linear theory. Sinusoidal waves preceded a turbulent burst which possessed an essentially plane front as it traveled downstream. As the Reynolds number was increased the bursting rate increased and the flow eventually became completely turbulent.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):389-393. doi:10.1115/1.3447175.

The interaction between an air bubble in water (d0 = 10–30 mm) and a shock wave generated by a small detonator (0.8 g) is studied. On the basis of direct pressure measurements inside pulsating bubbles and simultaneous photographic recording of the diameter variations, the overall thermal behavior of the gas in the bubbles is determined. It is found that the pulsation process is nearly adiabatic for the bubble sizes considered. The measured maximum pressures inside pulsating bubbles are given as a function of bubble size and distance from the explosion. From these results, the total energy absorbed by a bubble is calculated as a measure of the attenuation effect of a single bubble on a shock wave.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1974;96(4):394-400. doi:10.1115/1.3447176.

The flow field in an inertial impactor was studied experimentally with a water model by means of a flow visualization technique. The influence of such parameters as Reynolds number and jet-to-plate distance on the flow field was determined. The Navier-Stokes equations describing the laminar flow field in the impactor were solved numerically by means of a finite difference relaxation method. The theoretical results were found to be in good agreement with the empirical observations made with the water model.

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Fluids Eng. 1974;96(4):401-403. doi:10.1115/1.3447177.
Abstract
Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster

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