Effects of multiple radial blowing around a circular jet

Abstract

An experimental investigation has been carried out to study the effects of radial blowing at strategic locations around a free primary circular jet at a Reynolds number (Re) of 8800 using hot-wire anemometry. It is shown that the exact locations of the blowing ports play an important role in determining the centerline velocity decay and turbulence levels, which reflects the gross mixing-enhancement effects. For the present case of constant blowing ratio (3%) for all configurations, the number of blowing ports decides the absolute velocities of radial blowing which will have differing influence on the jet potential core. It is noted that the best performing configurations are those possessing the least number of blowing ports which imply that sufficiently high blowing velocities are required for effectiveness. On the other hand, for the same number of blowing ports, equally-distributed radial blowing does not perform as well as non equally-distributed blowing. An attempt was made to emulate the mixing characteristics of non-circular jets by imparting blowing at locations where the corners/vertices are supposed to be and the results showed surprisingly good agreement with the results on non-circular orifice jets as presented by Mi et al. (2000). While the centerline velocity levels seemed to decay faster, it is possible that the jet may have been deflected such that the potential core may not be aligned along the centerline. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.