DOUBLE-DIFFUSIVE NATURAL-CONVECTION IN TRAPEZOIDAL ENCLOSURES

This paper presents some results of numerical and experimental study o f turbulent double-diffusive natural convection of a mixture of two ga ses in a trapezoidal enclosure with imposed unstable thermal stratific ation. The geometry and boundary conditions are selected to mimic an i dealised situation in underground coal gasification. In the computatio ns turbulent fluxes of momentum, heat and mass were modelled by standa rd and low-Re-number (Launder-Sharma) k-epsilon eddy diffusivity model s with inclusion of thermal and mass buoyancy. The computed mean veloc ity, temperature and concentration, show satisfactory agreement with m easurements, indicating that despite some deficiencies, the numerical model can reproduce most of the essential features of the process. (C) 1998 Elsevier Science Ltd. All rights reserved.