Comparison of modified kappa-epsilon turbulence models for buoyant plumes

The effect of buoyancy on the production and dissipation of turbulent kinet ic energy is investigated in variants of the popular k-epsilon turbulence m odel. The standard gradient diffusion model is considered for the scalar fl ux as well as a generalized gradient diffusion model. Also, the addition of the nonisotropic component of an algebraic stress model for the Reynolds s tresses is assessed. The relative significance of the various models and te rms are demonstrated using different combinations of the models, including the important flux Richardson correction term. The generalized gradient dif fusion and algebraic stress models are shown to give a strong increase in t urbulence production, although the effect on the flow can be largely contro lled by the coefficient of the flux Richardson term. Recommendations are ma de regarding optimum models and coefficients.