  In this study, we investigated numerically the backdraft phenomenon under
different gravity conditions and 4 openings using Fire Dynamics Simulator (FDS)
code. Four different opening geometries are studied under ten different gravity
conditions. As demonstrated by an earlier study in our group, backdraft is
established under different gravity conditions from 0.1 g to 1 g. The rate at
which oxygen reaches an ignition block in the enclosure in the presence of the
gravity current 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 nonlinearly.
Moreover, the smoke exiting the enclosure is a precursor for the onset of
backdraft, albeit with a short warning, allowing people on the outside to take
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 impact force.
