A comparative study of turbulence models in a transient channel flow

The performance of a number of low-Reynolds number turbulence models is evaluated against direct numerical simulations (DNS). All models are applied to an unsteady flow comprising a ramp-type excursion of flow rate inside a closed channel. The flow rate is increased linearly with time from an initial Reynolds number of 9308 (based on hydraulic diameter and bulk velocity) to a final Reynolds number of 29,650. The acceleration rate is varied to cover low, intermediate and high accelerations. It is shown that among the models investigated, the k-ε models of Launder and Sharma (1974) and Chang et al. (1995) [28] and the γ-Re_θ transition model of Langtry and Menter (2009) [38] capture well the key flow features of these unsteady turbulent flows. For the cases of low and intermediate acceleration rates, these three models yield predictions of wall shear stress that agree well with the corresponding DNS data. For the case of high acceleration, the γ-Re_θ model of Langtry and Menter (2009) [38] and the k-ε model of Launder and Sharma (1974) yield reasonable predictions of wall shear stress.