Numerical investigation of gravity effects on backdraft phenomena in an enclosure with varying geometries

TL;DR

This study numerically examines how varying gravity conditions and enclosure geometries influence backdraft phenomena, highlighting the nonlinear effects on ignition timing, smoke behavior, and heat impact, with implications for safety precautions.

Contribution

It provides new insights into the nonlinear effects of gravity on backdraft initiation, considering different geometries and opening configurations using FDS simulations.

Findings

Gravity strength affects ignition time nonlinearly.

Smoke exit patterns serve as early backdraft indicators.

Heat flow impact exceeds impact force in severity.

Abstract

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.