CFD Study of Large City Fires in Windy Conditions Relevant to Aerial Firefighting

If a big earthquake happens to occur in a city with wooden houses in windy conditions, city fires could cause enormous damages, while firefighting operations will be extremely limited. Aerial firefighting with water dumping is expected; however, it has not been commonly used in fighting earthquake-induced large city fires. An important problem is that the information concerning fire front combustion and circumstances over fire areas is unknown. Such information is highly needed for flight safety and strategy. Due to the difficulty of large real-scale experiments, information on large city fires is limited. CFD studies of large city fires in windy conditions were made, but the details have not yet been fully clarified. This paper studies the fire flows near the fire front and over fire areas using CFD simulations, for which the radiation and temperatures in windy conditions are particularly examined. The characteristics of radiative heat flux, tilt angle, temperature, and wind velocity under different parameters are investigated. The results show that if (3 × 3) burning houses near the fire front are successfully extinguished, the radiative heat flux reaching the houses downwind can be reduced drastically. The temperature at 300 m from the ground will be lower than 100 °C, and the radiation will also be very low, which may provide instructions for the safety of aerial firefighting.

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