Flow Induced Vibrations in Engineering Systems and the Control of Flow Induced Vibrations. Active Control of Vortex Shedding from Circular Cylinder by Rotary Cylinder Oscillations.

Abstract

The present paper describes a new active method for controlling vortex shedding from a circular cylinder in a uniform flow, using rotary cylinder oscillations controlled by the reference velocity signal in the wake with some phase lag. The effectiveness of this active method is evaluated by measuring the response of mean and fluctuating velocities in the cylinder wake and by visualizing the flow field around the cylinder. It is found that velocity fluctuations are reduced by the control at the optimum phase lag, while they are enhanced at the reverse phase. The maximum reduction of 30 percent in the reference velocity fluctuations is obtained with the optimum control, where the optimum value of phase lag and the feedback coefficient are adopted. The modification of the mean velocity profile and the reduction in the fluctuating velocities in the wake are measured under the optimum control and the corresponding variations in the visualized flow field are recognized, similar to the change observed under the control with cross-flow cylinder oscillations.