Co- and contrarotating streamwise vortices in a turbulent boundary layer

Abstract

A study was carried out on streamwise vortices in a turbulent boundary layer using computational fluid dynamics. The vortices were generated by either a single jet or an array of jets of coor contrarotating arrangement exhausting into the boundary layer. The effects of jet angle, velocity ratio, and spacing were studied. Results confirmed previous experimental observations of single vortex formation at a sufficient distance downstream of the jet exit, from the initial multiple vortices. The study found that jet skew angle variation from 60 to 90 deg did not cause significant changes in the overall flow features. The results also suggested that a high jet velocity ratio might not necessarily be effective for flow control. For the contrarotating jets, it was found that 1) they produced stronger vortices, 2) the circulation level was reduced with the jet spacing, and 3) the maximum vorticity level was not affected by the jet spacing. For the corotating jets, it was found that 1) the circulation level was not affected by the jet spacing and 2) the vortices decayed much faster than those of the contrarotating arrangement. Good comparison was obtained between the calculated circulation levels and previous measurements.