EFFECT OF ACOUSTIC EXCITATION ON FLOW OVER A PARTIALLY GROOVED CIRCULAR-CYLINDER

An experimental investigation was carried out on the how over a partia lly grooved circular cylinder over a Reynolds number range of 3 x 10(4 ) to 1.22 x 10(5) with and without acoustic excitation. Without excita tion the dow over the smooth half of the cylinder was observed to shif t to higher subcritical regime. The flow over the groove half, however , is shifted to supercritical or transcritical flow regime. With excit ation, on the smooth half it is the separated laminar shear layer whic h locks in with the excitation frequency, resulting in the shift from subcritical to supercritical or transcritical regimes. On the groove h alf excitation is not effective for the flow within the transcritical regime. With excitation, the lift is found to reverse its direction wh ile the drag is nearly the same.