COHERENT CONTRIBUTION TO TURBULENT MIXING OF A JET IN CROSS-FLOW

In this work, an experimental study of a jet issuing in cross flow is reported. Support is offered to a theory on the origin of Karman-like vortices, in the wake of jets issuing in boundary layers. Further, a c oherent structure with strong contribution to the energetics of the fl ow field is identified here. This structure has not been reported earl ier, according to the present authors' knowledge, and it is shown to b e related to engulfment of external fluid at the bottom of the jet, an d to. interesting stochastic and spectral characteristics of the flow field. Three-dimensional plots of the coherent quantities, based on ex perimental data, reveal a double-helical morphology of the coherent st ructure. The same morphology has recently been proposed for the far fi eld of jets issuing in stagnant fluid (i.e., without cross flow). The results of this study are expected to support theoretical and numerica l work on jets issuing in cross flow.