Recent results with grey-area improved DDES for a wide range of flows

Abstract

At the previous HRLM Symposium we presented a novel DES-based approach [4] 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 σ LES model of Nicoud et al. [6]) 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. [11]. 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.