Computation of fire induced flow and smoke coagulation

Mathematical models for the calculation of the dynamics of smoke and hot gases induced by enclosure fires are presented. The models predict the evolution of the size distribution of smoke aerosol under the influence of coagulation, as well as the large scale fluid motion and temperature fields. The calculations contair three main ingredients: a finite difference solution of a hydrodynamics problem, the computer evaluation of an exact solution to the aerosol coagulation equation, and a Lagrangian particle tracking scheme to imbed the coagulation dynamics in the hydrodynamics. The hydrodynamics model is a time dependent variable density, two dimensional, infinite Grashof number flow driven by a prescribed heat source. No turbulence model is employed; the large scale eddy motion is calculated directly from the equations of motion. The mathematical particles each represent a large ensemble of aerosol particles, distributed initially in size according to the experimentally observed Junge distribution. They are introduced into the spatial grid in a random fashion near the heat source. The subsequent evolution of the size distribution in space and time is calculated deterministically from the solution to the Smoluchowski equation for the size distribution and the Lagrangian equations of motion for the spatial coordinates. Sample results of the hydrodynamic and aerosol properties are presented. Comparisons between calculations and relevant experiments are shown.