A two-scale low-Reynolds number turbulence model

Abstract

A two-scale low-Reynolds number turbulence model is proposed. The Kolmogorov turbulence time scale, based on fluid kinematic viscosity and the dissipation rate of turbulent kinetic energy (ν, e), is adopted to address the viscous effects and the rapid increasing of dissipation rate in the near-wall region. As a wall is approached, the turbulence time scale transits smoothly from a turbulent kinetic energy based (κ, e) scale to a (ν, e) scale. The damping functions of the low-Reynolds number models can thus be simplified and the near-wall turbulence characteristics, such as the e distribution, are correctly reproduced. The proposed two-scale low-Reynolds number turbulence model is first examined in detail by predicting a two-dimensional channel flow, and then it is applied to predict a backward-facing step flow. Numerical results are compared with the direct numerical simulation (DNS) budgets, experimental data and the model results of Chien, and Lam and Bremhorst respectively. It is proved that the proposed two-scale model indeed improves the predictions of the turbulent flows considered