Mixed subgrid scale models for classical and variational multiscale large-eddy simulations on unstructured grids
Part of the
book series (ERCO, volume 15)
The scale similarity (SS) idea was first introduced by Bardina et al. (1980). Following this idea the subgrid-scale stress tensor can be modeled through the modified Leonard tensor, which can be computed as a function of the variables resolved in LES by means of the application of an additional explicit filter. In the original idea, this filter should be the same as the grid one. It has been shown in a priori tests in the literature (see (Meneveau and Katz, 2000) for a review) that the SS model correlates very well with the exact SGS stress tensor and represents quite well energy backscatter from the unresolved to the resolved scales. However, when the scale-similarity SGS model is used alone in actual large-eddy simulations, it does not provide enough SGS dissipation and the simulations may undergo numerical instability. Therefore, the modified Leonard tensor (or SS term) is always used in combination with an eddy-viscosity term, leading to the so-called mixed models (Meneveau and Katz, 2000).
KeywordsUnstructured Grid Wale Model Scale Similarity Smagorinsky Model Numerical Viscosity
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