Impact of rainfall on smoke dynamics in longitudinally ventilated tunnels: model-scale fire test study

Abstract This study investigates the impact of rainfall on smoke dynamics and critical velocity in longitudinally ventilated tunnels through model-scale fire tests. The results show that the maximum ceiling excess temperature decreases as ventilation velocity increases. When rainfall is present, the maximum ceiling excess temperature initially increases and then decreases with higher rainfall intensity. A prediction model has been developed to evaluate the impact of rainfall on the maximum ceiling temperature. The temperature distribution on the side where rainfall occurs is not affected by rainfall itself but is determined solely by ventilation velocity. Additionally, a model has been proposed to predict the decay of the ceiling temperature on the rainfall side. The decay of ceiling temperature on the ventilation side is not influenced by rainfall parameters or fire power when tunnel airflow is primarily driven by either rainfall-induced airflow or ventilation airflow. The presence of rainfall requires a higher critical velocity, and a model for predicting critical velocity has been proposed considering rainfall intensity. This study contributes to our understanding of smoke dynamics in tunnel fires under rainfall conditions and provides valuable insights into smoke control during adverse weather.