Experimental investigations of rotor-fuselage aerodynamic interactions

This paper presents wind tunnel experiments of helicopter rotor-fuselage interactions. Several tests have been conducted in the ONERA F1 subsonic wind tunnel on a Dauphin 365N model equipped with a powered main rotor. Numerous measurements have been performed during these tests: time-averaged and time-dependent fuselage pressure measurements, six-components balance measurements, and particle image velocimetry (PIV) measurements. This last technique allows measurements of instantaneous velocity field in large planes around the helicopter for several blade positions during rotor revolution. 2-component PIV results and 3-component stereoscopic PIV results are presented. For each measurement technique accuracy and repeatability are first discussed, thanks to the large number of test points performed. The influence of the rotor downwash on the fuselage and the location of its impingement are then presented by analyzing the test points for different advance ratios and rotor thrust coefficients. The PIV results give a detailed description of the rotor wake in the presence of the helicopter fuselage.