The effect of streamwise vortices on a turbulent boundary layer exposed to an unsteady adverse pressure gradient

This experiment studied the effect of streamwise vortices on a turbulent boundary-layer exposed to an unsteady adverse pressure gradient in a water tunnel at a momentum thickness Reynolds number of 1840. The streamwise vortices were created by three pairs of half-delta wing vortex generators, while impulsively initiated opposite-wall suction created a strong adverse pressure gradient. The time response of the freestream velocity is characterized by two time scales, an initial fast response throughout the boundary layer which is unaffected by the presence of vortex generators, followed by a slow or convective response, the magnitude of which is substantially modified by the presence of the vortex generators.