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EDITORIAL

J. Fluids Eng. 1975;97(1):1. doi:10.1115/1.3447211.
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Abstract
Commentary by Dr. Valentin Fuster

REPORTS

J. Fluids Eng. 1975;97(1):2. doi:10.1115/1.3447212.
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Abstract
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):5-6. doi:10.1115/1.3447216.
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Abstract
Topics: Cavitation
Commentary by Dr. Valentin Fuster

COMMENTARY

J. Fluids Eng. 1975;97(1):3-4. doi:10.1115/1.3447214.
Abstract
Topics: Propellers
Commentary by Dr. Valentin Fuster

LETTERS TO THE EDITOR

J. Fluids Eng. 1975;97(1):7. doi:10.1115/1.3447221.
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Abstract
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Fluids Eng. 1975;97(1):9-38. doi:10.1115/1.3447225.

Wind has always had a strong influence, both unfavorable and favorable, upon man and his activities. Within the last decade needs for treatment of wind effects from an engineering point-of-view have increased tremendously. Losses due to wind ($500,000,000 in property damage, 240 deaths and 2600 injuries annually), increased demand and concern for human comfort, serious attempts to control air pollution, and the development and expansion of energy-production capabilities have resulted in applications of engineering to problems for which a body of knowledge has only started to emerge in the United States. The primary elements of this body of knowledge are found in the disciplines of meteorology, fluid mechanics, aerodynamics, and structural mechanics—organizing this knowledge to form a coherent subject-matter base for wind engineering is a real challenge for fluids engineers. The objectives of this review are to establish an initial subject-matter base for wind engineering, to demonstrate current capabilities and deficiencies of this base for an engineering treatment of wind-effect problems, and to indicate areas of research needed to broaden and strengthen the subject-matter base. Focusing of subject matter for wind engineering is accomplished through a historical summary of relevant scientific and technological material, an examination of information on wind characteristics, and a review of current capabilities for physical modeling of winds and wind effects in the laboratory. Current methods and capabilities in wind engineering are demonstrated by a review of problems related to atmospheric advection and dispersion of air pollutants, wind forces on buildings and structures, and control of winds. Research needs are specified separately for each area reviewed -wind characteristics, simulation of the wind, atmospheric transport of air pollutants, wind forces, and wind control. Physical modeling of boundary-layer-type winds and wind effects by measurements on small-scale models placed in long-test-section, meteorological wind tunnels currently provides the most reliable source of data for wind engineering. Coordinated measurements on full-scale systems and their small-scale models are necessary for continued confirmation of similarity for the laboratory data and for development of new modeling capabilities. In particular, development of a tornado simulator is an urgent need to support structural design for nuclear-power-plant facilities. Intensive analytical investigations of three-dimensional, thermally-stratified, turbulent boundary layers; separation of turbulent, unsteady flows; turbulent shear flow over bluff bodies; and interacting turbulent flows with a variety of turbulence characteristics are needed to ensure future progress in wind engineering. These investigations are needed to provide a framework for correlation of both laboratory and full-scale data, to support efforts to develop numerical modeling as a practical tool, and to develop a better understanding of the physical processes involved. These flow problems represent formidable frontiers of turbulent fluid motion. Therefore, investigations in the fluid-mechanics laboratory coupled with measurements on full-scale systems are expected to be the primary sources of information for wind engineering in the immediate future.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):39-50. doi:10.1115/1.3447213.

The Navier-Stokes equations and the equation of continuity describing the flow in the flat-faced nozzle-flapper valve are numerically solved by the iterative relaxation method and the effect of the flow contraction (vena contracta) occurring in the radial gap in the valve is investigated. Furthermore, an approximate formula for the flow force acting on the flapper is derived on the basis of the numerical solutions. The formula for the flow force is in good agreement with experimental results.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):51-59. doi:10.1115/1.3447215.

Mixing of a turbulent jet with a coaxial slower-moving secondary stream in a constant diameter tube was investigated. Of special interests were the effects of swirling the jet and initial turbulence kinetic energy. The analysis involved a numerical solution of the governing flow equations which were simplified by the Prandtl boundary layer assumptions. The two unknown turbulent stresses in the flow equations were modeled by defining an isotropic effective viscosity. The effective viscosity was calculated from a two-equation model of turbulence. The turbulence model was modified for swirling flows. Predicted results were compared with experimental results of several investigators. Good agreement was obtained when calculated results were compared with mean velocity and wall pressure data. The addition of swirl to the jet increased the rate of spread of the jet and resulted in decreasing the axial length required for mixing. The initial turbulence levels of the streams were found to have a significant effect on the distribution of mean velocity and pressure. This dependence has not been considered by most investigators and makes it imperative that experimentalists include turbulence information in their presentation of results.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):60-66. doi:10.1115/1.3447217.

Potential flow, control volume, and frozen vorticity models have been used to analyze the wall jet-receiver system. The potential flow model predicts well the extent of the region of influence upstream of the receiver entrance for jet widths the same order as the receiver width, but the assumption of irrotationality drastically mispredicts the receiver spill flow angle. A control volume model which accounts for the extent of influence upstream of the receiver entrance and the possibility of continuous wall stall accurately predicts the receiver spill flow angle for most receiver spill flow ratios. The frozen vorticity model predicts velocity profiles in the receiver entrance region reasonably well, and slightly overpredicts the pressure recovery coefficient in the receiver entrance region.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):67-70. doi:10.1115/1.3447218.

Present speed control governors for hydroelectric installations employ constant gain settings. This paper develops appropriate gain functions of load level for optimal (deadbeat sense) transient response throughout the operating range. The results coincide with the Paynter numbers for the special case of best efficiency operation and consider the null conduit and reverse blading effects as additional special cases.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):71-77. doi:10.1115/1.3447219.

The dependence of ion-chamber current on the density of the filling gas has been investigated, experimentally and analytically, to explore the use of an ion chamber as a high-pressure gas densitometer. A flat-plate ion chamber with a self-contained beta-particle source (Sr90 -Y90 ) was used in experiments with methane, nitrogen, and carbon dioxide and for pressures up to 2000 psia and densities up to 9 lbm/ft3 . Over an appreciable density range, the linearity of the current-density response was good with a static sensitivity of about 10−10 amp/(lbm/ft3 ) and a reproducibility of ±0.5 percent. Variables which could be used to increase the static sensitivity and the linear range were identified.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):78-81. doi:10.1115/1.3447220.

The author has found a class of entry velocity profiles that develop into the Raithby fully developed second solution for flow in a parallel porous plate channel with strong suction. The entry profiles of interest are characterized by a velocity defect at the channel centerline. Two numerical solution techniques are employed. The faster first technique involving solution of the boundary layer equations is used to predict overall trends of profile development. The boundary layer solutions are compared to exact solutions of the Navier-Stokes equations. A detailed examination was made of the double Poiseuille entry condition which was found to develop into Raithby’s profile.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):82-86. doi:10.1115/1.3447222.

Boundary layer transition on an axisymmetric body up to Reynolds number of 1.26 × 106 was observed by schlieren method of flow visualization developed for water tunnel use. The spectrum of the flush mounted pressure transducer signal showed a dominant frequency to exist at transition and further, this frequency was in close agreement with the predicted critical frequency by Smith’s approximate method of transition calculation based on linear stability theory.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):87-96. doi:10.1115/1.3447223.

Water table flow visualization tests of a straight wall diffuser and corresponding ribbed diffuser were conducted over a wide range of total divergence angles and diffuser length to throat width ratios. Rib parameters such as inter-rib cavity depth to width ratio, inter-rib cavity width, rib thickness, and number of ribs were varied, as well as rib contour. Motion pictures were obtained of the secondary flow patterns occurring within the inter-rib cavities, and hot film measurements were made to determine the extent of velocity fluctuations induced by the cavities. In general, the addition of ribs increased the no-appreciable stall regime.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):97-105. doi:10.1115/1.3447224.

An efficient procedure is developed for simulating frequency-dependent friction in transient laminar liquid flow by the method of characteristics. The procedure consists of determining an approximate expression for frequency-dependent friction such that the use of this expression requires much less computer storage or computation time than the use of the exact expression. The derived expression for frequency-dependent friction approximates the exact expression very well in both time and frequency domains. Calculated results for a test system are compared with the experimental results so show that the approximate expression predicts accurately the surge pressures, pressure wave distortion as well as pressure attenuation in a liquid line.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):106-111. doi:10.1115/1.3447182.

The motion of a medium consisting of an incompressible viscous fluid and suspended solid particles was analyzed from the standpoint of continuum mechanics. It was assumed that the particles’ translational and rotational velocities were different from those of the fluid. A numerical scheme was used to determine the non-equilibrium particulate flow properties as well as their equilibrium and frozen values. The results are presented for the case of particulate flow due to the impulsive motion of an infinite flat plate in a suspension. A demixed region, with no particles present, was found to develop near the plate due to particle migration away from the wall. Similar demixed particle regions were noticed in the experimental data of particulate flows in pipes and channels.

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):113-116. doi:10.1115/1.3447184.

Velocities up to 200 m/s in condensing steam flows have been successfully measured using a laser Doppler anemometer, without artificial seeding. The performance of the system is described and results are compared with simultaneous pitot tube measurements. The discrepancy between the alternative methods used here for converting pitot pressure to velocity in subsonic wet flow becomes greater at higher speeds; extension of this work is discussed, with the objective of calibrating pitot tubes for use at high subsonic and low supersonic speeds encountered in low pressure turbines.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):116-117. doi:10.1115/1.3447186.
Abstract
Topics: Force , Fluid dynamics
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):117-119. doi:10.1115/1.3447187.
Abstract
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):119-120. doi:10.1115/1.3447188.
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):122-124. doi:10.1115/1.3447190.
Abstract
Topics: Swirling flow
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):124-126. doi:10.1115/1.3447191.
Abstract
Topics: Flow (Dynamics)
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):126-129. doi:10.1115/1.3447192.

The two-dimensional momentum integral equation is derived for the case where free-stream turbulence or ordered unsteadiness exist. It is shown that extra terms may arise, of which one, the shear stress at the edge of the boundary layer, is important.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1975;97(1):135. doi:10.1115/1.3447208.
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Abstract
Topics: Fluids , Turbulence

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