Turbulent Eddies in the RANS/LES Transition Region.

Hybrid RANS/LES methods combine the advantages of RANS models in terms of simulation costs, with the ability of LES to capture unsteady flow structures. A problem encountered in applications of this technique is the transmission of information between the RANS and LES zones: in the RANS region only mean-flow data is available, and the Reynolds shear stresses are entirely supported by the turbulence model; in the LES region, on the other hand, turbulent eddies must be present to support the turbulent momentum transport. The generation of these eddies is a critical ingredient in determining the effectiveness and accuracy of a hybrid method. In this paper we discuss this problem for applications in which the RANS region is below the LES zone, and in cases in which the flow advects from RANS to LES regions. We will also present recent results from our research group. [ABSTRACT FROM AUTHOR]