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Some Comments on the Modeling of the Collapsing Wake

Author: E. Y. T. Kuo

Publisher:

Published: 1972

Total Pages: 12

ISBN-13:

The problem of scaling the phenomena of the collapse of the wake of a self-propelled body in a stratified fluid is examined. Conditions are derived such that the Froude number (based on body speed, length and Vaisala period) is equal for both model and prototype. Conditions are also obtained for the existence of buoyancy and inertial subranges in the wake turbulence. These conditions are applied to determine the smallest size model for which the phenomenon of wake growth and collapse is properly scaled from the prototype. (Author).

Some Comments on the Modeling of the Turbulent Wake of a Self-Propelled Body in a Stratified Fluid

Author: Edward Y. T. Kuo

Publisher:

Published: 1972

Total Pages: 14

ISBN-13:

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The modeling of the turbulent wake of a self-propelled body in a stratified fluid is discussed. The scaling parameter is taken to be the internal Froude number, using the speed and diameter of the body and Vaisala frequency of the fluid. The ratio of the time for the wake to collapse to the characteristic time of the turbulence is related to model scale when the wake is turbulent up to and including the collapse. A number of criteria for turbulent wake are discussed. Numerical estimates are made, assuming typical values of the model speed and of the Vaisala frequency, of the minimum model size necessary for the existence of a turbulent wake at collapse.

Scientific and Technical Aerospace Reports

Author:

Publisher:

Published: 1987

Total Pages: 920

ISBN-13:

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Wake Collapse and Subsequent Generation of Internal Waves in a Density Stratified Medium

Author: Jin Wu

Publisher:

Published: 1968

Total Pages: 106

ISBN-13:

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An experimental technique was developed to model a two-dimensional mixed region collapsing in a continuously density-stratified medium. The process of this mixed region can be divided into three stages. Empirical formulae were derived to describe the process of the first two stages, during which densimetric effects determine the modeling criterion. The collapse process in the final stage is complicated by viscous effects including mixing at the thin wake tip. The pattern of the internal waves generated by the initial impulsive collapse of the mixed region was studied; it can be represented by moving rays connecting either wave crests or troughs. These rays move away from the collapse center and at the same time decrease their slopes. A simpler steady state wave pattern generated by an oscillating plunger was also studied. Taken together, these experimental results are interpreted to show that the energy density of the initial impulsive collapse is skewed toward higher frequencies and that it is peaked at 8/10 of the Brunt-Vaisala frequency. The mechanism underlying the moving ray patterns is explained. (Author).

MRIS Abstracts

Author: Maritime Research Information Service

Publisher:

Published: 1973

Total Pages: 810

ISBN-13:

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Collapse of Turbulent Wakes in Density-stratified Media

Author: Jin Wu

Publisher:

Published: 1965

Total Pages: 50

ISBN-13:

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The wake generated by a submerged body moving through a density-stratified medium consists not only of a region of turbulence but also of a region of water with homogeneous density. The purpose of the present research is to study phenomena and modeling criteria relating to the collapse of this wake. Since the wake is very slender in the direction of the body passage, this problem is simplified by studying only the collapse of a particular transverse section of the wake. An experimental technique was successfully developed by using a wall-mixer to model the collapsing phenomen of a two-dimensional wake in densitystratified media. The process of collapse can be divided into three stages: 'initial', 'principal' and 'final' collapse stages. Empirical formulae were derived to describe the collapse processes of the first two stages, during which the gravitational effect is found to be the predominant modeling criterion. The collapsing process in the final stage was complicated by the increasing viscous effect and observed mixing at the thin wake tip. (Author).