Active Control of the Profile Drag of Two-Dimensional Cylinders

Abstract

The control of profile drag on a circular cylinder was studied experimentally at Reynolds numbers, ranging from 160 to 400, using an acoustic active control system. The investigation has been carried by, quantitatively, hot-wire to measure the mean and fluctuating velocities and, qualitatively, by using smoke-wire flow visualization technique to examine the formation of the flow field down-stream of the cylinder. The present active control method is able to influence the rate of entrainment from main flow into the wake flow. When the Reynolds number is relatively small, it is the size of the cylinder and the induced sound field velocity as well as Reynolds number which are the significant parameters in determining the controlling reverse and optimum phase lag angels. The reported control strategy is able to alter the profile drag of a two-dimensional circular cylinder. At optimum lag angle and low Reynolds number the profile drag was reduced by 9%.