Experimental Velocity Fields Evaluation under the Rotor/Propeller Interactions for High Speed Helicopters for Different Propeller Positions

This paper focuses on the experimental evaluation of the rotor/propeller interactions for hybrid compound configurations. Experiments are conducted in the ONERA L2 large size-low speed wind tunnel with a 1/7.7 Dauphin 365N model and a four-bladed small-scale propeller. PIV measurements are performed to visualize the velocity fields around the helicopter. Different flight conditions (wind speeds, and propeller position) are tested. In hover, the propeller is completely immersed in the rotor wake for all the configurations, and the thrust is therefore maximal. At low speed, the propeller is partially immersed and the flow on the propeller disk is highly asymmetrical. In this flight configuration, moving the propeller towards the tail of the device increases the interactions and thus the performances of the propeller. No direct interactions of the two rotating parts are measured at high speed for all the configurations tested.