PREDICTION AND MEASUREMENT OF THE AERODYNAMIC INTERACTIONS BETWEEN A ROTOR AND AIRFRAME IN FORWARD FLIGHT

Results of a detailed study of aerodynamic interactions are summarized. The test case is a two-bladed, rigid teetering rotor above a hemisphere-cylinder airframe in low-speed forward flight. A multi-faceted set of measurements, including surface pressures, thrust, flow velocity, and vortex trajectories has been acquired and used to develop and validate a potential-flow method to predict such interactions. The salient features of the measurements and the prediction method are summarized. The test case shows strong interaction effects. The interaction problem is seen to be dominated by unsteady, but mostly periodic, effects. The potential flow method is seen to be capable of predicting the dominant features of the interaction, in an azimuth-resolved fashion, under these conditions. However, it is inadequate to explain the details of the interaction of the strong vortices from the rotor with the airframe surface.