Estimating the Spread of Fire in Buildings

Abstract

AWE is developing a general fire modelling capability at a city scale and want to upgrade their current capability by incorporating suitable building-scale models into the simulation. The main question that needs answering is: given an initial state in which fires are known to be burning in a particular location or region of a building of given dimensions, is it possible to determine estimates for the rate at which fire spreads throughout this building? In particular, estimates for the temperature at the outer walls as a function of time.
This report addresses the problem in three ways. First, the state of the art in the literature on fire modelling is reviewed and a mid-complexity model (referred to as “the Kyoto model”) which treats rooms as individ- ual compartments is recommended for further study. This is then sim- plified into an ODE compartmentalised model only those processes that are believed to be essential. A fully dimensional version of the model is developed including estimates for all the physical paramaters. After nondimensionlisation, the model is simulated for a building comprising a chain of rooms separated by fire doors. Finally, a homogenised reaction- diffusion PDE model is developed in one and two space dimensions. In this model walls are treated as areas of greater porosity. Simulation results reveal the sensitivity of the fire spread to the internal layout of the building. These final two models have both been implemented as a Matlab and C-code deliverable respectively.