Physics-based urban fire spread simulation coupled with stochastic occurrence of spot fires

Abstract

This paper presents the development and validation of physics-based urban fire spread simulation coupled with stochastic occurrence of spot fires. When a fire occurs in densely-built wooden residential area, the fire easily spreads to adjacent buildings because of the narrow distance between buildings. Although the fire in weak winds is usually extinguished by firefighters before developing into large-scale fires, the fire in strong winds sometimes overwhelm the firefighting capability because of the occurrence of spot fires. Numerous firebrands that are released from burning buildings travel a long distance by strong winds and cause new fire ignitions far from the burning buildings, which are referred to as the spot fires. Actually, firefighters have suffered from the spot fires in the past great urban fires in Japan, such as the Itoigawa fire in 2016. From such an experience, there have been calls for the use of urban fire spread simulation in planning of firefighting operation in strong winds. Therefore, we have been developing a physics-based urban fire spread model including the stochastic occurrence of spot fires. Here, in order to validate the model, we numerically simulated the fire spread in wooden residential area in Itoigawa City using Monte Carlo method and compared the calculated results with the fire damage in 2016. From the calculated results, we concluded that the proposed model could reasonably explain the number of spot fires that occurred in the Itoigawa fire, and could simulate the urban fire spread conservatively in terms of the fire spread rate.