A TURBULENCE MODEL FOR WIND FLOWS ABOVE FIRE AREAS

The object of the present work is to model the wind flow field above fire areas. A cylinderical domain of height H and radius Ro is considered with a concentric fire area of radius Rf at its bottom. The rate of heat flux within the fire radius Cr is specified. Averaged Reynolds equations for momentum and the thermal energy equation are solved together with the transport equations for the kinetic energy of turbulence k and its rate of dissipation E. Buoyancy effects on both the mean motion and turbulence are considered. The turbulent momentum and thermal diffusivity at the bottom boundary are based on the Monin-Abukhov length scale L for the given buoyancy flux SIG. The set of equations is solved in the primitive form by an explicit numerical method on a staggered mesh. Marching through time the solution is proceeded until a steady state solution is obtained. Pressure iterations are carried out at each computational step to satisfy the mass conservation equation. The model results are compared with experimental values of a physical model for fire plumes. The model also predicts the three components of wind mean velocity pressure, potential temperature, density deficit as well as turbulence kinetic energy and its rate of dissipation at different locations of the flow domain. The effects of surrounding environmental circulation are also predicted for different values of bottom heat flux Q".