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Turbulence and Shear Flow Phenomena -1 First International Symposium

ISBN:
1-56700-135-1 (Print)

LOCALIZED UNSTEADY BLOWING AND NEAR WALL TURBULENCE CONTROL

Sedat Tardu
Laboratoire des Ecoulements Geophysiques et Industriels (LEGI) UMR 5519/Universite de Grenoble 38402 Saint mrtin d'heres Cedex France

Abstract

The effect of time-periodical blowing through a spanwise slot on the near wall turbulence characteristics is investigated. The blowing velocity changes in a cyclic manner from 0 to 5 wall units. The frequency of the oscillations is equal to the median frequency of the wall turbulence. The flow field near the blowing slot is partly relaminarized during the acceleration phase of the injection velocity until 40 wall units downstream. The imposed unsteadiness is confined into the buffer layer and the time mean structural parameters under unsteady blowing are found close to those of an isotropic turbulence in this zone. The relaminarized phase is unstable and gives place to a coherent spanwise structure which, in return, increases the shear from 80 to 300 wall units downstream of the slot in a predictible way.