Effect of Compressibility on Suppression of Dynamic Stall Using a Slotted Airfoil

A multielement airfoil designed for helicopter application has been tested for compressible dynamic stall behavior and has been proven to be a robust dynamic stall-free concept. This slotted airfoil has operated into poststall areas without the dynamic stall vortex that is normally present whenever airfoils are tested beyond their static stall boundary. Point diffraction interferogram images of the dynamic flow over the airfoil are presented, showing details of the flow development during the oscillation cycle, and instantaneous pressure distributions on the airfoil and slat during dynamic airfoil motion are included