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Horizontal jets and vortex dipoles in a stratified fluid

Published online by Cambridge University Press:  26 April 2006

S. I. Voropayev ,
Ya. D. Afanasyev  and
I. A. Filippov
S. I. Voropayev
Affiliation:
Institute of Oceanology, USSR Academy of Sciences, Krasikova 23, Moscow 117218, USSR
Ya. D. Afanasyev
Affiliation:
Institute of Oceanology, USSR Academy of Sciences, Krasikova 23, Moscow 117218, USSR
I. A. Filippov
Affiliation:
Institute of Oceanology, USSR Academy of Sciences, Krasikova 23, Moscow 117218, USSR
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Abstract

When a horizontal force is applied locally to some volume of a viscous densitystratified fluid, flows with high concentration of vertically oriented vorticity (vortex dipoles) are generated. The processes of generation and evolution with time of these unsteady flows in a stratified fluid are studied. A convenient way to produce and study these flows in the laboratory is to use a submerged horizontal jet as a ‘point’ source of momentum. The main governing parameter (the ‘force’) is easily controlled in this case. Two regimes were studied: starting jets with dipolar vortex fronts (the force acts continuously) and impulsive vortex dipoles (the force acts for a short period of time). A conductivity microprobe, aluminium powder, shadowgraph, thymol-blue and other techniques have been used to measure the velocity and density distributions in the flows. It is found that in both regimes the flows are self-similar: the lengthscale of the flows increases with time as t½ for starting jets and as t1/3 for vortex dipoles. Detailed information about the generation mechanism, kinematics and dynamics of the flows is obtained. On the basis of similarity principles a theoretical explanation of the experimental results is given. The theory is in good agreement with the results obtained.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 227 , June 1991 , pp. 543 - 566
Copyright
© 1991 Cambridge University Press

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