A Comparision between CFD and Wind Tunnel Measurements for Wake Vortex Prediction

A comparative investigation on the wake vortex evolution of a large transport aircraft has been conducted by means of simulations using the DLR{TAU code and by hot{wire anemometry in a wind tunnel as part of the EC funded project FAR{Wake. In order to judge the in uence of the wind tunnel two calculations of the aircraft have been conducted, one in free ight and one in the wind tunnel. Di�erences in the lift distribution of the two cases cause mainly di�erent positions of the trailing vortices. Also, an additional vortex around the front portion of the peniche of the half model can be found in the wind tunnel case. A comparison of the results obtained for the fuselage by simulation and measurement leads to grid and simulation parameters for wake vortex simulations. High order turbulence modeling together with grid adaptation delivers a highly accurate simulation result which is almost identical in comparison to the wind tunnel measurement. Using this the entire aircraft has been simulated in free ight and compared to wind tunnel results in terms of non{ dimensional axial vorticity. The overall ow �eld and e�ects are represented quite well, whereas the peak vorticity values are clearly under predicted due to a still too coarse mesh. This can be solved, as shown for the fuselage case, by further grid adaptation, which is still very costly and time consuming on present super{ computers