Modelling fire smoke dynamics in a stairwell of high-rise building : effect of ambient pressure

Abstract

In a high-rise building fire, vertical shafts are the main paths for hot smoke to spread to multiple floors, posing a significant fire hazard. In this work, the large eddy simulation (LES) was applied to simulate smoke dynamics in a full-scale stairwell and study the influence of ambient pressure and heat release rate (HRR). The results have shown that the air mass flow rate into the stairwell decreases as ambient pressure drops on account of the lower air velocity and density and increases with HRR because of the stronger stack effect and increased smoke production. An equation incorporating ambient pressure and HRR is proposed for predicting the air mass flow rate. The temperature of hot smoke near the fire source increases with the reduced ambient pressure, while on the floors away from the fire source, the temperature decreases due to the higher temperature attenuation at a lower pressure. In addition, an empirical model is put forward for predicting the rising time of the smoke plume considering ambient pressure. The results could increase the basic understanding of smoke movement mechanisms and contribute to engineering applications of smoke control in high-rise building fires under reduced ambient pressure conditions.