A new formulation of scale-adaptive simulation approach to predict complex wall-bounded shear flows

Abstract

A new formulation of scale-adaptive simulation (SAS) approach for complex wall-bounded shear flows is presented. This approach makes use of a unique modelling representation and requires moderate computational costs. Based on the Rotta original transport equation for turbulence integral length scale, the suggested model is able to resolve unsteady turbulent structures with sufficient spatial resolution. Similar to the classical SAS-turbulence model (SST–SAS) proposed by Menter et al. [5] that represents an improvement of the proven turbulence model for unsteady calculations, the new model appears advantageous where classical LES (large eddy simulation) or hybrid LES–RANS models are too expensive. However, in its zonal formulation, the new model provides accurate predictions in (1) so-called stable flows (e.g. channel flow) in which the classical SAS () model will not be able to switch from Reynolds-averaged Navier–Stokes (RANS) to scale-resolving simulations without an explicit introduction of synthetic turbulence, (2) flows with relatively weak instabilities also challenging for the classical SAS-type models (e.g. swirling flow with sudden expansion). Such improvements result from the appropriately treating additional source terms in modified transport equation of dissipation rate. For demonstration, comparisons with experimental data and direct numerical simulation are provided.