SUMMARYA hybrid LES-RANS modelling approach is proposed. RANS is used in the near wall regions (y + . 60), and the turbulence is modelled with a k-! model. LES is used in the remaining part of the ow, and the SGS turbulence is modelled with a one-equation ksgs model. The same continuity and momentum equations are solved throughout the domain, the only di erence being that the turbulent viscosity is taken from the k-! model in the RANS region, and from the one-equation ksgs model in the LES region. The new modelling approach is applied to two incompressible ow test cases. They are fully developed ow in a plane channel and the ow over a 2D-hill in a channel.

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A low Reynolds number (LRN) formulation based on the Partially Averaged Navier-Stokes (PANS) modelling method is presented, which incorporates improved asymptotic representation in near-wall turbulence modelling. The effect of near-wall viscous damping can thus be better accounted for in simulations of wall-bounded turbulent flows. The proposed LRN PANS model uses an LRN k −ε model as the base model and introduces directly its model functions into the PANS formulation. As a result, the inappropriate wall-limiting

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A modified form of Wilcox’s low-Reynolds-number k-ω model (Wilcox, 1994) is proposed for predicting recirculating flows. The turbulent diffusion for the specific dissipation rate, ω, is modeled with two parts: a second-order diffusion term and a first-order cross-diffusion term. The model constants are re-established. The damping functions are redevised, which reproduce correct near-wall asymptotic behaviors, and retain the mechanism describing transition as in the original model. The new model is applied to channel flow, backward-facing step flow with a large expansion ratio (H/h = 6), and recirculating flow in a ventilation enclosure. The predictions are considerably improved.