Numerical computations of steady and unsteady, separating, buoyant flows - Part II: Computations with a low-Reynolds-number k-epsilon model

摘要

Numerical computation has been performed to determine the influence of buoyant effects on convective flows with the standard k-epsilon and the low-Reynolds-number k-epsilon models. Results obtained with both turbulent models are compared with the available experimental data. In this work, Kolmogorov velocity, u(epsilon) = (vepsilon)(1/4), is introduced instead of shear velocity, u(tau) = roottau(w)/rho, to avoid the singularity that appears at the separating and reattaching point for both turbulence models. Turbulent Prandtl numbers were allowed to vary in the low-Reynolds-number k-epsilon model to mimic the experimental data. Buoyant effects have been investigated with various Richardson numbers for the backward-facing step flow. Various separation patterns as well as vortex shedding were observed beyond a critical Richardson number. In addition, the required grid configration for accurate results for the low-Reynolds-number k-epsilon model has been discussed for the backward-facing step flows. [References: 20]