Active Wake Control of Flow Past a Circular Cylinder with Slot Jet

Abstract

In the current research, an active-flow control scheme characterized by leeward slot jet over a circular cylinder was experimentally investigated to manipulate the vortex shedding from the cylindrical test model and stabilize the unsteady cylinder wake. A slot installed on the leeward stagnation point of the circular cylinder was used to implement steady jet. The experimental research was conducted in a wind tunnel at a subcritical Reynolds number (Re) of 2.17×104. The high-speed particle image velocimetry (PIV) system was utilized to visualize and analyze the vortical structures in the wakes of the baseline and controlled cylinders to evaluate the effectiveness and mechanism of the active slot jet control technique with various equivalent blowing momentum coefficient Cμ. Experimental results reveal that the slot generates a pair of symmetric jet vortices that interact with the sheared layer from the cylinder wall, which thus modifies effectively the flow features in the cylinder wake. With such dynamic interactions, the unsteady separation flows rolled up from the upper and lower surfaces of the test model are elongated and push the alternating vortex shedding downstream. Owing to the convection between the jet vortices and the cylindrical wake vortical structures, a modal transition from asymmetric to symmetric of the cylinder wake was realized. It is also shown that the flow characteristics such as Reynolds shear stress and turbulent kinetic energy are controlled to be quite low. Furthermore, a linear stability analysis is carried out to imply that the stability characteristics in the flow field behind the cylindrical model can be manipulated by the blowing slot jet.