A two-scale low-Reynolds number turbulence model

In this study, 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 (nu, epsilon), is adop ted 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 (k, epsilon) scale to a (nu, epsilon) scale. The damping functions of the low-Reynolds n umber models can thus be simplified and the near-wall turbulence characteri stics, such as the E distribution, are correctly reproduced. The proposed t wo-scale low-Reynolds number turbulence model is first examined in detail b y predicting a two-dimensional channel flow, and then it is applied to pred ict a backward-facing step flow. Numerical results are compared with the di rect numerical simulation (DNS) budgets, experimental data and the model re sults of Chien, and Lam and Bremhorst respectively. It is proved that the p roposed two-scale model indeed improves the predictions of the turbulent fl ows considered. Copyright (C) 2000 John Wiley & Sons, Ltd.