Development and validation of a physics-based urban fire spread model

A computational model for fire spread in a densely built urban area is developed. The model is distinct from existing models in that it explicitly describes fire spread phenomena with physics-based knowledge achieved in the field of fire safety engineering. In the model, urban fire is interpreted as an ensemble of multiple building fires; that is, the fire spread is simulated by predicting behaviors of individual building fires under the thermal influence of neighboring building fires. Adopted numerical technique for the prediction of individual building fire behavior is based on the one-layer zone model. Governing equations of mass, energy, and chemical species in component rooms are solved simultaneously, for the development of temperature, concentrations of chemical species, and other properties. As for the building-to-building fire spread, three mechanisms are considered as contributing factors of fire spread, i.e., (I) thermal radiation from fire-involved buildings; (II) temperature rise due to wind-blown fire plumes; and (III) firebrand spotting. As for the model verification, fire spread simulations were carried out in a hypothetical urban area, where 2500 buildings of identical configuration were aligned at constant separations. Calculated fire spread rates were then compared with that of the Hamada model, and reasonable agreements were obtained. The model was further verified with the record of a past urban fire, which took place in the city of Sakata in 1976. Although the general features of the fire spread were similar, there were certain discrepancies in the eventual burnt area. The reasons for these discrepancies were discussed and issues for future refinements were stated. (C) 2007 Elsevier Ltd. All rights reserved.