Forschung im HLRN-Verbund 2011

117Figure 1: Visualization of vortex structures around the vehicle model in cross-wind conditions (vortices are coloredwith the streamwise velocity: red = high velocity, blue = low velocity).rameter space it requires a large number of simulationruns. Thus the authors considered a statisticallydesigned set of simulations based on orthogonalarrays. In such a way the number of requiredsimulations can be drastically reduced. Theinfluence of each parameter can be determinedand at the end an optimum control setup can beconcluded. In the future the authors would like todevelop, similarly to the above mentioned robustclosed-loop controller, a new method, which will beable to track the prescribed drag reduction with anasymmetric (more than one output parameter) actuationsetup successfully, also in case of crosswindconditions.A visualization of the LES simulation result isshown in fig. 1 for cross-wind conditions without actuation.In the figure vortex structures are shownthat have been colored by the local velocity. Thesnapshot indicates the level of complexity of thisflow. This simulation requires approximately 72hours of wall clock time on 270 processor coresof the HLRN system in order to reach an adequatelevel of time averaging.More Information1. Ahmed, S.R., Ramm, G. and Faltin, G., Somesalient features of the time-averaged ground vehiclewake, SAE Technical Paper Series, No.840300, 1984.2. Eichinger, S., Thiele, F. and Wassen, E., LESof active separation control on bluff bodies bysteady blowing, Proceedings of ASME 20103rd Joint US-European Engineering SummerMeeting, August 2-4, 2010, Montreal, Quebec,Canada, FEDSM-ICNMM2010-30462.FundingGerman Research Foundation (DFG)Ingenieurwissenschaften