Significance of generating synthetic turbulence for zonal detached eddy simulation of shallow water flows

Abstract

A zonal detached eddy simulation (ZDES) is suitable for large-scale open-channel flows with a free surface, e.g. river flow. In ZDES, only a local region is required to be investigated using large eddy simulation (LES) to obtain a high resolution of vortical structures in hydraulic engineering. In this study, a fully non-hydrostatic free-surface flow model is developed for a ZDES-type model. The focus is to analyse the critical strategy of the turbulent forcing method, which is very important for the ZDES-type model. A well-validated synthetic eddy method was established using a numerical framework and applied to generate velocity fluctuations. Based on the synthetic turbulent velocity, a new formulation of the body force term was fed into the momentum equations. A test case of a fully developed open-channel flow with a free surface was used to verify the numerical strategy. Then, another common flow problem of a free-surface flow over a fixed dune was adopted to further validate the numerical approach. The results show that the proposed numerical strategy can promote the application of the hybrid Reynolds-averaged Navier–Stokes/LES method in natural large-scale open-channel flow simulation.