Role of synthetic jet frequency & orientation in dynamic stall vorticity creation

Vorticity creation and its evolution play an important role in the formation of large dynamic stall vortices which cause large excursions in lift, drag and pitching moment on rapidly pitching and oscillating airfoils. While synthetic jets have shown potential in controlling dynamic stall vortices by sustaining lift increases without corresponding drag and pitching moment, their effect on the vorticity creation remains unknown. To address this, high fidelity computational fluid dynamics simulations were conducted to investigate how synthetic jet frequency and orientation alter the dynamic stall leading-edge boundary vorticity flux. Changes in baseline boundary vorticity flux were related to corresponding flow fields to delineate the role of synthetic jets in vorticity creation. Slot orientation was found to play a greater role in altering the amount of vorticity diffused into the flow than actuation frequency. Dynamic stall vortex sizes were found to be directly proportional to the vorticity diffused from the leading-edge and could therefore be effectively manipulated using synthetic jets. The study provides a better understanding of the dynamic stall vorticity creation process and its control using synthetic jets.