Instantaneous Flow Field Measurements for Propeller Aircraft and Rotorcraft Research

This paper illustrates of instantaneous flow field measurements which were performed by the PIV group of DLR Göttingen during test campaigns in three different wind tunnel facilities of the Dutch-German Wind Tunnel foundation (DNW). The test results described first were obtained in the low speed tunnel LST in order to obtain detailed flow field information about the wake of a new high speed propeller model. The second test was performed in the transonic wind tunnel TWG in the frame of a German helicopter research project. Here the flow field above a pitching airfoil equipped with a flap driven by an integrated piezoelectric actuator has been observed with high spatial resolution. During the third test, stereoscopic flow field measurements were performed in the wake of a rotorcraft model in order to characterize the blade tip vortices at different flight conditions. The test was conducted in the 6x8m² open jet test section of the large low speed facility LLF which required observation distances exceeding 9 meters between camera and light sheet