Recent Results with Grey-Area Improved DDES for a Wide Range of Flows
At the previous HRLM Symposium we presented a novel DES-based approach  that addresses one issue frequently encountered for hybrid RANS-LES methods, i.e. the delayed transition from RANS to LES in separated shear layers also known as the grey area. The approach is based on employing a different sub-grid scale model (i.e. the \(\sigma \) LES model of Nicoud et al. ) for the LES mode of delayed DES (DDES), which offers an ameliorated behaviour in the crucial early shear layer region. Results are presented for basic calibration cases as well as a range of complex applications featuring different flow topologies, where a comparison is drawn to a current state-of-the-art hybrid method, i.e. standard DDES of Spalart et al. . The new DDES variant is found to improve predictive accuracy significantly for cases strongly impacted by the grey area (e.g. a compressible round jet, flow over delta wing) and at the same time maintains key advantages of the original DDES method, such as its non-zonal nature and its capability to shield attached RANS boundary layers.
This work has been financed by the EU FP7 project “Go4Hybrid” (ACP3-GA-2013-60536-Go4Hybrid). The authors would also like to thank M. Shur & M. Strelets (NTS, Russia) and J. Kok (NLR, the Netherlands) for their generous provision of computational grids and advice for the jet and delta wing test cases.
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