On the Hybrid RANS-LES of Compressible Flows
The formulation of a RANS-LES method for compressible flows faces many fundamental problems. The usual adoption of mass weighted, Favre, averages in the RANS region, and filtered Favre averages in the LES region produces additional difficulties to the connection of the RANS and LES zones, and the dialogue between RANS and LES quantities, both as regards the post processing of data and the formulation of bridging RANS-LES closures, is not so easy. In this paper this problem is explored on the basis of the operational filtering approach that with the introduction of the generalized central moments gives a unified averaging invariant formulation both of RANS and LES. The extension of this approach to the mass weighted averages will be discussed and a mixed RANS-LES system of equations will be presented.
KeywordsCompressible Flow Turbulent Channel Flow Subgrid Stress Favre Average Mass Weighted Average
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