Explicit Algebraic subgrid-scale models for LES

Authors: Rasam, A., Brethouwer, G.B., Johansson, A.V.J.
Document Type: Conference
Pubstate: Unknown
Journal: Proc. of 9th Int. ERCOFTAC Symp. on Engineering Turbulence Modelling and Measurements (ETMM9)
Year: 2012


The explicit algebraic subgrid stress model (EASSM) has been introduced recently byMarstorp et al. (2009). The EASSM improves the prediction of the individual subgrid-scale (SGS) stresses and gives large-eddy simulation (LES) predictions that are less resolution dependent in comparison with isotropic eddy viscosity SGS stress models (Rasam et al. 2011). In the first part of the paper, we present LES results of turbulent channel flow at Re = 934 and 2003 using the EASSM and compare its performance to that of the dynamic Smagorinsky model (DSM) of Germano et al. (1991). We show that the EASSM predictions are much less resolution dependent and more accurate than those of the DSM at both Reynolds numbers. In the second part of the paper, we present a new explicit algebraic subgrid scalar flux model (EASSFM) for LES of passive scalar transport. The new model is derived from the explicit algebraic scalar flux model of Wikstrom et al. (2000) for Reynolds averaged Navier–Stokes equations. The new model is derived from the modeled transport equation of the SGS scalar flux and has a tensorial eddy diffusivity formulation which uses the strain rate, rotation rate and the subgrid stress tensors in its formulation . The new model predictions of the SGS scalar fluxes are not necessarily aligned with the resolved scalar gradient. Therefore, it can predict SGS fluxes arising from the mean shear. The EASSFM is validated for the case of heat transfer in streamwise rotating turbulent channel flow (with Prandtl number Pr =0.71 and friction Reynolds number Re_\tau =300).