Prediction of Horizontal and Vertical Turbulent Buoyant Wall Jets

Abstract

A buoyancy-extended version of the k – ε turbulence model is described which predicts well the main features of turbulent buoyant wall jets. The model relates the turbulent shear stress and heat flux to the mean velocity and temperature gradients respectively and to the turbulent kinetic energy k and the dissipation rate ε by way of the Kolmogorov-Prandtl eddy viscosity/diffusivity relation and determines k and ε from semi-empirical transport equations. The empirical constant cμ in the Komogorov-Prandtl expression and the usually constant turbulent Prandtl number σt are replaced by functions which are derived by reducing model forms of the Reynolds-stress and heat-flux transport equations to algebraic expressions, retaining the buoyancy terms and the wall-damping correction to the pressure-strain/scrambling model in these equations. The extended k – ε model is applied to buoyant wall jets along a horizontal wall and to α plume developing along a vertical wall. The predictions are compared with experimental data whenever possible and are found to be in good agreement with the data.