CONTROL OF THE SEPARATED FLOW DOWNSTREAM OF A 2-DIMENSIONAL FENCE BY LOW-FREQUENCY FORCING

Streamwise distributions of wall shear-stress, reverse-flow-factor and static pressure were measured in the turbulent separation regions ups tream and downstream of a two-dimensional fence. In front of the fence , boundary layer profiles were measured with a pulsed-wire probe trave rsing out of the wall. The flow was then manipulated by a periodic dis turbance which was located upstream of the forward separation region. Two different disturbances were tested: an oscillating spoiler and a t wo-dimensional oscillating jet with zero mean mass flow driven by a lo udspeaker. Both manipulators were orientated parallel to the fence. Wi th appropriate tuning of the parameters, the reattachment length behin d the fence could be reduced by 50%.