In large eddy simulation (LES), the filtering grid scale (FGS) of LES equations is calculated generally by local mesh size. Therefore, proper LES Meshing is very decisive for better results and more economical cost. An effort was made to provide an available approach for LES meshing by turbulence theory and CFD methods. The expression for proper filtering grid scale (PFGS) was proposed on the basis of −5/3 law of inertial sub-range. A new parameter named grid ratio coefficient was put forward for the mesh adjustment. The proper mesh of LES could be built directly from the adjustment of RANS mesh. Two test cases both backward facing step flow and turbulent channel flow were provided to verify the approach. There were three kinds of mesh size, including coarse mesh for RANS (RCM), adjusted mesh for LES with the novel approach (NAM) and fine mesh for LES (LFM), employed here. The grid numbers of NAM were less than those of LFM evidently, and the results of NAM were in a good agreement with those of DNS and experiments. It was also revealed that results of NAM were very close to those of LFM. The conclusions provided positive evidences in the application of the approach.

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