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Mixing layer produced by a screen and its dependence on initial conditions

Published online by Cambridge University Press:  20 April 2006

Hakuro Oguchi  and
Osamu Inoue
Hakuro Oguchi
Affiliation:
Institute of Space and Astronautical Science, Komaba 4-6-1, Meguro-ku, Tokyo 153, Japan
Osamu Inoue
Affiliation:
Institute of Space and Astronautical Science, Komaba 4-6-1, Meguro-ku, Tokyo 153, Japan
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Abstract

This paper aims to elucidate the structure of the turbulent mixing layers, especially, its dependence on initial disturbances. The mixing layers are produced by setting a woven-wire screen perpendicular to the freestream in the test section of a wind tunnel to obstruct part of the flow. Three kinds of model geometry are treated; these model screens produced mixing layers which may be regarded as the equivalents of the plane mixing layer and of two-dimensional and axisymmetric wakes issuing into ambient streams of higher velocity. The initial disturbances are imposed by installing thin rods of various sizes along the edge of the screen or at the origin of the mixing layer. Flow features are visualized by the smoke-wire method. Statistical quantities are measured by a laser-Doppler velocimeter. In all cases large-scale transverse vortices seem to persist, although comparatively small-scale vortices are superimposed on the flow field in the mixing layer. The mixing layers are in self-preserving state at least up to third-order moments, but the self-preserving state is different in each case. The growth rates of the mixing layer are shown to depend strongly on the initial disturbance imposed.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 142 , May 1984 , pp. 217 - 231
Copyright
© 1984 Cambridge University Press

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