Airfoil pressure measurements during a blade vortex interaction and a comparison with theory

A two-dimensional, airfoil-vortex interaction experiment was conducted to obtain the aerodynamic behavior of the airfoil during a parallel interaction. The vortex was created by pitching a second airfoil placed upstream and parallel to an instrumented test airfoil. Hot-wire anemometer measurements were taken to determine the vortex velocity distribution. The interaction tests were conducted for a counterclockwise vortex passing above a symmetrical airfoil at zero angle of attack. Pressure transducers located inside the test airfoil measured steady and unsteady airfoil pressure distributions. Time histories of the lift, drag, and moment coefficients were determined from the measured pressure distributions. These results are compared to an analytical study using an unsteady, discrete-vortex, potential-flow theory.