Helicopter Downwash/Frigate Airwake Interaction Flowfield PIV Surveys in a Low Speed Wind Tunnel

The work presented was performed at Old Dominion University and is part of a larger research program aimed at identifying interactions between rotor downwash and ship airwakes. The ODU Low-Speed Wind Tunnel was used with a simplified 1/50 scale frigate waterline model and traverse mounted powered rotor. Particle Image Velocimetry (PIV) velocity surveys were compared with rotor thrust coefficient measurements at locations of identified interaction to help understand the underlying flow physics. Initially, PIV surveys of the frigate model landing deck in isolation and the rotor in isolation were performed to provide a baseline flow understanding. A PIV flowfield survey was conducted with the ship in isolation, rotor in isolation and then the combined ship/rotor cases in order to compare superposed individual velocity fields to a combined measurement. Tests were performed with and without the presence of a rotary wing downwash influence on the landing deck centerline (y=0) for a wind-over-deck angle (WOD) of zero.