Gravity Effects on Backdraft Phenomena in an Enclosure with Varying Opening Geometries

Abstract

In this study, we investigated the backdraft phenomenon numerically under different gravity conditions and 4 openings using the Fire Dynamics Simulator (FDS) code. Four different opening geometries are studied under ten different gravity conditions. The rate at which oxygen reaches an ignition block in the enclosure in the presence of gravity currents plays an important role in the onset of ignition, the subsequent backdraft formation, and the maximum pressure built inside the enclosure before the onset of backdraft. This role also explains why these effects are different under different openings. We observe that the gravity strength affects the ignition time and the onset of backdraft non-linearly. Moreover, it is found that the smoke exiting the enclosure cannot be considered a reliable precursor for the onset of backdraft to allow people on the outside to undertake necessary precautions. The effect of backdraft in the form of heat flow and impact force at the exit is also studied. It is found that the effect of heat flow is more severe than that of the impact force.