Turbulent flow simulation using LES with dynamical mixed one-equation subgrid models in complex geometries

An innovative computational model is presented for the large eddy simulation of multi-dimensional unsteady turbulent flow problems in complex geometries. The main objectives of this research are (i) to better understand the structure of turbulent flows in complex geometry and (ii) to investigate the 3D characteristics of such complex fluid flow. The filtered Navier-Stokes equations are used to simulate large scales of the turbulence, while the energy transfer from large scales to subgrid-scales (SGS) is simulated using dynamical mixed one-equation subgrid models. In the proposed SGS model, the SGS kinetic energy, k s g s , is used for scaling the velocity for the eddy-viscosity part of the model. The proposed SGS model contains not only some information on the small scales as described in traditional Smagorinsky model or Germano dynamical model but also includes additional scale-similarity as that in the models of Ghosal et al. (J. Comput. Phys. 1995; 118:24-37) or Davidson (11th International Symposium on Turbulent Shear Flow, Grenoble, vol. 3, 1997; 26.1-26.6). The Navier-Stokes equations and the derived k sgs equation are solved using implicit finite-volume method. The models have been applied to simulate the 3D flows over a backward-facing step and in a strong 3D skew runner blade passage of a Francis hydro turbine, respectively. Good agreement between simulated results and experimental results as well as other numerical results was obtained.