コルモゴロフ速度スケールに基づく壁面ダンピング関数を利用したLES

抄録

The usage of a wall-damping function based on Kolmogorov velocity scale in large eddy simulation (LES) is investigated. To calculate Kolmogorov velocity scale, the dissipation rate of turbulent energy, ε, is needed. In LES, however, the dissipation rate is not solved unlike in the k-ε model, and we have to take the statistics of the calculated unsteady data to obtain it. Therefore, the usage of the wall-damping function in LES is not straightforward. In some studies, the dissipation rate of the subgrid-scale (SGS) turbulent energy, ε_SGS, is used instead of ε. However, since the SGS components contain only the turbulent components in the scale smaller than the grid-filter width, the damping effect becomes inappropriate and dependent on the grid resolution employed. To overcome this problem, we propose a method for estimating ε from ε_SGS, where the ratio of two length scales, one in LES and the other in the k-ε model, is used. The revised wall-damping function using the estimated ε is tested in canonical channel flows, and the results show that it gives proper near-wall damping effect in every case with considerably wide range of grid resolutions.