Active Feedback Interaction with a Shear Layer.

Abstract : Work continues on the characterization of the effects of a pitching airfoil on the shear layer structure and growth under open loop forcing. We have shown that locally introduced disturbances can induce significant changes in the growth of the shear layer mixing zone. A separate investigation into the structure of the wake of an oscillating airfoil in a steady, uniform free stream revealed the existence of an axial flow along the cores of the wake vortices. The magnitude of the axial flow appears to depend on both the frequency and amplitude of oscillation.