Pans simulations: low versus high reynolds number approach

Different approaches for specifying the ratio of modelled-to-total dissipation ( fε) in the PANS model, based on the k −ω SST model, are evaluated for different ratios of the modelled-to-total kinetic energy, fk. Based on theoretical reasoning it is argued that applying fε = a · fk should have little effect, and that fε = fk is not expected to improve the results. This is confirmed by applying the approaches to a turbulent channel flow at Reτ = 395 and 180, and comparing the results to the often used ‘high Reynolds number’ approach ( fε = 1.0). Reducing fε leads to a reduction in range of scales in the flow; dissipation is allowed at larger scales and therefore smaller scales are suppressed.