Resumen de Physics-based Modeling of Fire Spread in Densely-built Urban Area and its Application to Risk Assessment
Keisuke Himoto, Takeyoshi Tanaka
A fire staring in a densely-built urban area easily spreads to adjacent buildings.
Especially, in the case of a large earthquake, in which multiple fires may break out simultaneously, the momentum of fire spread may easily overwhelm the ability of firefighters and cause disastrous damage to the area. It is recently reported that there are substantial area still left in Japan which requires some social intervention for improving safety from fire spread. In this study, fire spread simulations were carried out in order to investigate behavior of fire spread in Kyoto Higashiyama area, one of the representatives of densely-built urban areas in Japan. In the numerical model, urban fire is assumed 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, following mechanisms are considered as contributing factors of fire spread: thermal radiation heat transfer from fire-involved buildings; thermal convection by windblown fire plumes originated from fire-involved buildings in the upwind; and spotting ignition by dispersed firebrands. With this numerical model, the risk of fire spread in Kyoto Higashiyama area was assessed by the Monte Carlo method. Effectiveness of measures against fire spread was also investigated by comparing results of the risk assessment.
