A mixed one-equation subgrid model for large-eddy simulation

A new mixed one-equation subgrid-scale (SGS) model for large-eddy simulation is presented. The scale-similarity part of the model is used for the description of the local energy transport (Domaradzki et al., 1993, 1994), i.e. the energy transport between scales very close to the cut-off. The eddy-viscosity part of the model represents the non-local transfer of energy, i.e. the transfer between all scales smaller than grid-filter size Δ and larger than Δ. A priori tests done by Bardina et al. (1980) have shown a high correlation between the scale-similarity model and the exact SGS stress, τij. The magnitude of the scale-similarity part in the mixed one-equation SGS model is either larger than or equal to that of the eddy-viscosity part. The modeled SGS stress is thus expected to correlate well with the exact stress, τij. In the proposed model, the SGS kinetic energy, ksgs, is used to obtain the velocity scale for the eddy-viscosity part of the model. The modeled ksgs equation is derived and contains some additional scale-similarity parts as compared with the ksgs equation used in the models of Ghosal et al. (1995) or Davidson (1997). It has been shown that the model is Galilean invariant and realizable. Moreover, the approximately correct near-wall behavior of the model has been proven. The model was tested for both channel flow and the case of a surface-mounted cube (Martinuzzi and Tropea, 1993). It was found that the model gives accurate results in both cases.