The Shape of Two-dimensional Turbulent Wakes in Density-stratified Fluids
The Shape of Two-dimensional Turbulent Wakes in Density-stratified Fluids

Author: Roy Hayden Monroe

Publisher:

Published: 1968

Total Pages: 85

ISBN-13:

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The results of an analytical and experimental investigation of the rate of growth of the zone of turbulent mixing behind a two-dimensional circular cylinder are presented. The analytical phase of the study formulated a dynamical model for a parcel of fluid subjected to inertia, turbulent damping, and gravity restoring forces. The experiments were conducted in a tank 120 in. long and 4.5 in. wide which was filled to a depth of 18 in. with a fluid having a linear density gradient. The cylinder was towed at mid-depth by a variable speed motor-pulley system. A record of wake growth behind the cylinder was made by means of motion pictures of an aluminum pigment tracer in the fluid. The Reynolds number ranged from 1300 to 3500 and densimetric Froude numbers varied from 5 to 20. The density stratification was found to exert a strong inhibiting force on the wake growth. Using the dynamical model to correlate experimental data, the mixing length in the turbulent zone was found to decrease with increasing density stratification. (Author).

The Shape of Two-dimensional Turbulent Wakes in Density-stratified Fluids
The Shape of Two-dimensional Turbulent Wakes in Density-stratified Fluids

Author:

Publisher:

Published: 1968

Total Pages: 85

ISBN-13:

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The results of an analytical and experimental investigation of the rate of growth of the zone of turbulent mixing behind a two-dimensional circular cylinder are presented. The analytical phase of the study formulated a dynamical model for a parcel of fluid subjected to inertia, turbulent damping, and gravity restoring forces. The experiments were conducted in a tank 120 in. long and 4.5 in. wide which was filled to a depth of 18 in. with a fluid having a linear density gradient. The cylinder was towed at mid-depth by a variable speed motor-pulley system. A record of wake growth behind the cylinder was made by means of motion pictures of an aluminum pigment tracer in the fluid. The Reynolds number ranged from 1300 to 3500 and densimetric Froude numbers varied from 5 to 20. The density stratification was found to exert a strong inhibiting force on the wake growth. Using the dynamical model to correlate experimental data, the mixing length in the turbulent zone was found to decrease with increasing density stratification. (Author).

Turbulent Wakes in Density Stratified Fluids of Finite Extent
Turbulent Wakes in Density Stratified Fluids of Finite Extent

Author: Edmund A. Prych

Publisher:

Published: 1964

Total Pages: 65

ISBN-13:

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Results are presented of an investigation of the effects of a free surface and density stratification of the turbulent transfer of mass and momentum in two-dimensional wakes. The effect of depth of submergence on the drag of a twodimensional body was also investigated.

The Growth of a Turbulent Wake in a Density-stratified Fluid
The Growth of a Turbulent Wake in a Density-stratified Fluid

Author: Walter P. M. van de Watering

Publisher:

Published: 1966

Total Pages: 116

ISBN-13:

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The force of gravity causes a turbulent wake in a density-stratified fluid to eventually cease its vertical growth and then to collapse towards its horizontal midplane. In the present investigation this phenomenon was studied experimentally. The turbulent wake was created by means of a spiral paddle, agitated by a pendulum-type arrangement outside a transparent lucite tank. Data were obtained from tracings of the motion pictures taken by a 16 mm movie camera. Both the pendulum arrangement and the paddle diameter were varied to find the possible influence of the experimental conditions. It was observed that the initial rate of growth in the vertical direction is constant, depending primarily on the density gradient and the agitation mechanism (i.e. pendulum and paddle diameter). This initial rate of growth of the wake, the maximum vertical thickness of the wake, the time at which collapse begins and the turbulence intensity within the wake at that time, were all correlated with the Vaisala frequency, resulting in three important constants which seemed to be independent of the experimental conditions. (Author).

Experiments on Turbulent Wakes in a Stable Density-stratified Environment
Experiments on Turbulent Wakes in a Stable Density-stratified Environment

Author: Walter P. M. van de Watering

Publisher:

Published: 1969

Total Pages: 74

ISBN-13:

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In a laboratory experiment, turbulent mixed regions were generated in a linearly density-stratified fluid and their behavior was studied. Such regions may occur in nature in the atmosphere and in the ocean. Particularly during their early history, the shape of such regions is influenced by the interacting effects of turbulence and buoyancy, culminating in the occurrence of a maximum thickness and subsequent vertical collapse. A Richardson number (equivalent to the ratio of the characteristic turbulence time and the Vaisala period) was found satisfactorily to correlate the data obtained, together with those previously obtained by other investigators with self-propelled bodies. An estimate is made of the degree of mixing that takes place inside a turbulent mixed region during its growth in stably-stratified surroundings: the effectiveness of this mixing determines the ultimate thickness to which the mixing region collapses. (Author).

Turbulence Models and Their Application in Hydraulics
Turbulence Models and Their Application in Hydraulics

Author: Wolfgang Rodi

Publisher: CRC Press

Published: 1993-01-01

Total Pages: 124

ISBN-13: 9789054101505

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This book provides an introduction to the subject of turbulence modelling in a form easy to understand for anybody with a basic background in fluid mechanics, and it summarizes the present state of the art. Individual models are described and examined for the merits and demerits which range from the simple Prandtl mixing length theory to complex second order closure schemes.

Three-dimensional Momentumless Wakes in Density-stratified Liquids
Three-dimensional Momentumless Wakes in Density-stratified Liquids

Author: Philip Joseph Stockhausen

Publisher:

Published: 1966

Total Pages: 80

ISBN-13:

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Experiments were performed to investigate the configuration and surface effects of the turbulent wake generated by a self-propelled body moving in a linearly density-stratified liquid. The experiments were performed in a 50-foot long tank filled to a depth of 2 1/2 ft. For all experiments, the Reynolds number, based on the diameter of the circular disc mounted on the model's bow, was 89,000. It was found that the mixed region generated by the turbulent wak5 rapidly attained a maximum vertical extent, and then collapsed vertically while continuing to expand laterally. The vertical collapse of the wake was accompanied by the convergence toward the model of the fluid at the free surface. The convergence did not occur with homogeneous liquids. It was concluded that this surface convergence is possible only if the turbulent wake extends to the free surface. A new method was developed for generating linear density profiles in large tanks. (Author).