Active control of flow over backward facing step by synthetic jets

Experimental measurements of time-averaged Reynolds stress and skin friction by means of a constant temperature hotwire anemometer and sublayer fences respectively were conducted for flow over a backward facing step with and in absence of active control by synthetic jets. Some possible parameters of the employed synthetic jet, including forcing frequency, synthetic jet direction and location, were discussed to investigate their effects on the separated free shear layer created by the recirculating region and reattachment process downstream of the step. Results showed that the spreading rate of the separated mean flow was increased significantly in the forced flow. Considerable changes in the Reynolds stress components accompanied by a prominent increase in the skin friction and a significant decrease in the reattachment length were also observed by different configurations of synthetic jet.