On a Local Averaging of Model Coefficient in Large-Eddy Simulation

초록

An averaging technique to calculate the model coefficient of dynamic subgrid-scale modeling(DSGSM) is introduced. The technique is based on the concept of local averaging, and useful to stabilize numerical solution in conjuction with LES of complex turbulent flows. It is relatively simple to implement, and takes very low overhead in CPU time. It is also able to detect the region of negative model coefficient where the "backscattering" of turbulence energy occurs. We apply the technique to LES of turbulent channel flow with a square rib mounted on one wall. The Reynolds number is 3,400 based on the mean velocity above the obstacle and the obstacle height. Near-wall structures are resolved with the no-slip boundary condition. The results are compared with those of a DNS and a simulation without turbulence modeling. The results show improvements over the no-model simulation, indicating the validity of the averaging technique of the model coefficient of DSGSM in LES.