Separated flow upstream of a jet in a crossflow

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