A Numerical Model for Horizontal Flame Spread over Combustible Solid Fuels

A simplified numerical horizontal flame spread model for thermally thick fuels has been developed with the intention of being incorporated as a submodel of a larger Computational Fluid Dynamics (CFD) model, in order to make predictions of a burning fuel object in a full scale building fire. The model presented here is self contained, employing empirical models for the shape and size of the fire plume, and the combustion behaviour of the solid fuel in question.

The fuel surface is discretised on a regular rectilinear grid. Flame spread is determined by considering the ignition and combustion properties of each surface grid cell, with the spreading flame front modelled as a series of discrete ignitions. Physical factors considered in the model include surface temperature, flame heat radiation, three dimensional heat conduction within the solid, and mass loss from and subsequent regression of the fuel surface.

A series of full scale fire tests has been performed with slabs of standard polyurethane foam, and the flame diameter and rate of mass loss were measured. There is good agreement between the modelled and experimental results.