Effect of acoustic excitation on flow over a partially grooved circular cylinder

An experimental investigation was carried out on the flow over a partially grooved circular cylinder over a Reynolds number range of 3 × 10⁴ to 1.22 × 10⁵ with and without acoustic excitation. Without excitation the flow over the smooth half of the cylinder was observed to shift to higher subcritical regime. The flow over the groove half, however, is shifted to supercritical or transcritical flow regime. With excitation, on the smooth half it is the separated laminar shear layer which locks in with the excitation frequency, resulting in the shift from subcritical to supercritical or transcritical regimes. On the groove half excitation is not effective for the flow within the transcritical regime. With excitation, the lift is found to reverse its direction while the drag is nearly the same.This study is partly supported by a grant from the Committee of Research and Conference Grants. The University of Hong Kong