Empirical modelling of fire behaviour based on field data has resulted in significant advances in forest fire science and produced numerous research and operational decision support tools. This field-based research requires measuring of fire behaviour quantities, eg, rate of spread and flame geometry, in a number of outdoor experimental fires burned under a set of fuels and fire weather conditions. Ensuing modelling relies on regression analysis linking easily measurable fire environment variables with fire characteristics. Costs, safety constraints and the characteristics of the data collected in the field have somehow limited the inferences that can be drawn from the data. This has limited our understanding of some of the processes driving fire spread, namely fine-scale processes and fire-atmosphere interactions.

This paper will discuss a quasi-physical approach to fire behaviour modelling. The focus is combining basic physical processes with carefully planned experimental fires aimed at quantifying specific fire properties (eg, heat fluxes, flame flow rates, flame temperatures) that are currently unknown, but necessary for modelling and evaluating the physical processes necessary to close the quasi-physical model systems. We will present results from our experimental burning program, discussing new insights into flame phenomena and its integration into new fire behaviour models.