Wake Vortex Studies in the ONERA Catapult Facility and in the DNW Wind Tunnels

Abstract

As part of the European research programmes WAVENC and EUROWAKE the wake vortex system behind (i) a free flying Airbus model and (ii) the DLR's ALVAST half model has been investigated experimentally in the ONERA catapult facility and in the DNW-LLF (large low-speed wind tunnel facility) respectively. Digital particle image velocimetry (PIV) was used for both testing campaigns. The two facilities offer different experimental access to the physical phenomena of vortex formation, evolution and decay with one and the same measurement technique and require a particular adaptation of this measurement technique to the different test conditions each. In both cases tracer particles added to the flow were illuminated by a pulsed laser light sheet in a plane crosswise to the flight path of the model or to the main flow direction respectively. Two CCD cameras recorded neighbouring areas of the flow field simultaneously. The PIV system operation was fitted to the facilities' requirements. Image data were evaluated utilising the cross-correlation method. The resulting velocity and vorticity fields give quantitative information on the structure and motion of the trailing vortices in different frames of reference: a ground-based one for the catapult and a model's one for the wind tunnel