SEPARATED FLOW UPSTREAM OF A JET IN A CROSS-FLOW

The complex flow in the recirculation region upstream of a rectangular jet issuing normally into a uniform crossflow has been examined using flow visualization techniques. The variation of the primary separation distance with velocity ratio revealed the existence of two different flow regimes. The change from one to the other occurs at a velocity ratio of 5. The recirculation region upstream of the jet is found to be unsteady and periodic. The frequency of this periodic motion appears to be the same as that produced by the vortex shedding in the near wake. Depending upon the flow parameters, the wake behind the jet displays two distinct vortical structures, one dominated by a symmetric vortex pair, forming a closed region, and the other with vortices shed alternately from each side of the jet, similar in nature to the flow past solid bluff bodies. It is also shown that the Strouhal number based on the vortex shedding frequency varies uniquely with the velocity ratio. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.