Double-diffusive natural convection in trapezoidal enclosures

This paper presents some results of numerical and experimental study of turbulent double-diffusive natural convection of a mixture of two gases in a trapezoidal enclosure with imposed unstable thermal stratification. The geometry and boundary conditions are selected to mimic an idealised situation in underground coal gasification. In the computations turbulent fluxes of momentum, heat and mass were modelled by standard and low-Re-number (Launder-Sharma) κ-e eddy diffusivity models with inclusion of thermal and mass buoyancy. The computed mean velocity, temperature and concentration, show satisfactory agreement with measurements, indicating that despite some deficiencies, the numerical model can reproduce most of the essential features of the process.