LES-Langevin Approach for Turbulent Channel Flow

The LES-Langevin model was studied on turbulent channel flows. The approach is based on the dynamics of the subgrid velocity scales previously studied in the frame of Rapid Distortion Theory. The subgrid stress tensor is modeled through a combination of a turbulent force and an eddy-viscosity. The turbulent force equation is derived from the subgrid scales velocity dynamics within the hypotheses of the Rapid Distortion Theory. The complex nonlinear terms containing the subgrid scale pressure were modeled by a stochastic forcing. The well-known eddy-viscosity closure was chosen to improve the resolved scales dissipation due to subgrid Reynolds stress. The advantage of the model is that the dynamics of turbulent force is prescribed by a dynamical equation derived from the Navier–Stokes equations. This allows a possibility to include all the important physical effects of the subgrid scales like the backward subgrid scale energy transfer. The direct modeling of the gradient of the subgrid scale tensor allows a reduction of the computational time compared to direct numerical simulation, which is the global objective of LES. The work demonstrates a need for further investigation on the equation of the turbulent force in order to better estimate the subgrid scale action.