MODELING FIRE SPREAD THROUGH FUEL BEDS

This is a review of the essential ingredients needed to make a mathematical model of fire spread through a fuel bed. The physical problem is outlined in general terms. Previous models are classified as statistical, empirical, or physical in accordance with the methods used in their construction. Considerable attention is given to the many physical models proposed over the fifty years of model building. A unified mathematical treatment is presented, which permits a more objective comparison of the different physical models. The key theoretical and experimental expositions in the literature are interpreted as pointing to a missing ingredient for fire spread in still air: a short range heat transfer mechanism. A candidate for this is buoyant convection, which unfortunately is very difficult to model in terms of the fundamental fluid dynamic equations. However, the concept of turbulent transport by eddies can be of help here, resulting in flame spread rates which depend on values for the eddy diffusivity of the fuel bed.