New low-Reynolds-number k-ε turbulent model for natural and mixed convection in enclosed cavity

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.In the paper (Zhang et al. 2007) several RANS turbulent models were evaluated by classic natural convection experiment. It can be seen that V2f turbulent model show the best overall performance compared to the other models in terms of accuracy of temperature, velocity and turbulent kinetic energy. However, all compared turbulent models cannot simulate the pseudo laminar phenomenon in the centre zone of the classic natural convection experiment. Moreover, V2f model needs to solve four equations, and the transport equation for the wall normal stress ( v² ) and the elliptic equation for the relaxation function (f) make the model numerically unstable. Based on the idea of V2f model, an anisotropic model (BV2fAM) was developed. In the BV2fAM model, the v² as the turbulent kinetic intensity normal to streamlines, was still be adopted and computed by local turbulent kinetic energy and local flow characteristic variable instead of the v² transport equation. The developed BV2fAM model was testified by two benchmark cases (classic natural convection in a tall cavity, and mixed convection in a square cavity). It can be seen that the developed BV2fAM model can give much better simulated results of temperature, velocity and turbulent kinetic energy than other compared models. Moreover it can simulate the pseudo laminar phenomenon in the centre zone of the classic natural convection experiment.