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PASSIVE CONTROL OF THE TURBULENT FLOW AT THE OUTLET OF A CIRCULAR JET BY MEANS OF A CYLINDER

Ivan Antonini
Department of Mechanics and Aeronautics, University "La Sapienza" Via Eudossiana 18, 00184 Roma, Italy

Giovanni Paolo Romano
Department of Mechanics and Aeronautics, University "La Sapienza" Roma, 00184 Rome, Italy

Abstract

In this paper, the velocity field at the outlet of a circular jet is investigated experimentally. A long cylinder is placed at different positions in front of the nozzle to study if this passive device enhances mixing. The region within seven diameter from the nozzle is considered. The measurement technique which is used is the high speed Particle Image Velocimetry (PIV) which allows to derive sequences of instantaneous velocity fields and to average them. The cylinder, almost independently of its position, smoothes the large scale Kelvin-Helmholtz vortices. Especially when it is placed close to the centreline, it also spreads the jet flow into the ambient flow much more than the free jet condition thus enhancing mixing.