Osamu Imazeki

Computational Fluid Dynamics of Hot Current from a Fire Source near a Tunnel Wall

Numerical Simulation by CFD was carried out to understand the hot current behavior in a tunnel with longitudinal ventilation. It becomes clear that fire source modeling is very important because the hot current behavior is strongly affected by the fire source position and is sensitive to methods in the modeling of the fire source. The flame area which has developed from the fire source is an area of chemical reaction caused by combustion. Even if grids in the vicinity of the fire source are made fine, it was difficult to simulate the heat generation area with consideration to this chemical reaction through using a method for setting the heat release rate simply on the fire source surface. Therefore, we proposed a method adopting the knowledge on flame shape under the longitudinal ventilation and incorporating it into numerical simulation and it showed a good agreement with the experimental results. It was shown through experiments in a tunnel with longitudinal ventilation that the hot current developed toward the tunnel center downwind from the fire source near a wall. The cause was investigated by numerical simulation and it became clear from the results that the spiral air by the fire plume created a vortex in the crevice between the wall and the plume.