International Journal of Fluid Dynamics (1999), Vol. 3, Article
Turbulence control in wall jets: a visualisation
M. SCHOBER, F.
GREWE and H.H. FERNHOLZ
Straße des 17. Juni 135
10623 Berlin, Federal Republic of Germany
(Received 25 Feb 1999 and in Revised Form 31 March 1999; Publication
Date April 14 1999)
A new method for the control of the mixing of a plane turbulent wall jet
has been investigated. A thin wire, mounted in the vicinity of the wall-jet
nozzle, changes the formation of the shear-layer structures in the early
stages of the development of the wall jet. The wire is operated in two
ways: (1) A still wire inhibits the natural shear layer roll-up and reduces
the size of the turbulent structures and thereby the mixing; (2) A self-excited
oscillating wire introduces large coherent structures and thereby enhances
the mixing. The size of these structures does not depend on the shear-layer
instability but rather on the wire frequency.
Flow visualisations with paraffin vapour have been performed for these
cases. The Reynolds number based on the slot width was in the range of 2500Rej 10000.
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