Some Measurements on Dynamic Stall

Details of a flow oscillation device and of force and moment measurements on a 2 ft chord twodimensional NACA 0012-64 airfoil in the oscillating flow and oscillated in pitch in a steady flow through stall are presented. Results indicate that both methods give essentially the same description of the dynamic stall process. It is apparent from peaks in the pressure distributions and in the pitching moment traces that more than one vortex is shed from the leading edge during the stall process. This, coupled with the very rapid changes that occur during stall, requires very close scrutiny of force and moment data that has not been recorded continuously. Understanding of dynamic stall overshoot will not be complete until detailed measurements are obtained in the region of the laminar separation bubble near the nose.