High Reynolds number backward-facing step flow control

Abstract

The flow over a backward facing step is investigated at Reynolds numbers higher than that previously reported for both the natural response and with imposed periodic forcing emanating from the step top corner. Surface pressure measurements and surface flow visualisation were used to characterise the flow. It was found that no significant change to the reattachment length occurred over the range 1.18 × 10 5 < Re H < 4.72 × 10 5 . With imposed actuation, up to a 16% base pressure increase was observed with a corresponding 3% increase in reattachment length. For high forcing frequencies a reduction in base pressure near the top step corner, close to the actuator, was observed.