Streamwise vortices near a density interface

The interaction of streamwise vortices with a density interface is investigated by experiments and by computations of the stratified cavity flow. The flow pattern of the primary circulation is different from that of homogeneous fluid. The results show that the deepening of a mixed layer into a region of constant density gradient proceeds with three-dimensional deformation of the interface and that pairs of counter-rotating streamwise vortices appear in the strong shear layer near the interface. The comparison between the three-dimensional and two-dimensional computations indicates that this streamwise vortical structure contributes to mixing across the interface.