Effects of transverse fire locations on flame length and temperature distribution in a bifurcated tunnel fire

In this paper, a series of experiments were conducted in a 1:10 reduced scale bifurcated tunnel to investigate transverse flame length and temperature field distribution under the ceiling with different transverse fire source locations. Five fire locations were considered and the corresponding distances (D) between the fire source centerline and sidewall are 0.1 m, 0.3 m, 0.5 m, 0.7 m and 0.9 m respectively. It is found that the predicted value by Gao?s model overestimates the ceiling jet flame extension length, thus a modified correlation considering the influence of the branch tunnel is established, which includes a sidewall and non-sidewall region. Moreover, a simplified equation for predicting the dimensionless maximum ceiling jet temperature by taking transverse fire locations into account is developed based on Ji?s model. Besides, the longitudinal temperature decay coefficient in the main tunnel ceiling shows a non-monotonous trend with D, exhibiting a maximum value at the condition for D is 0.3 m. However, there is a linear relationship between the longitudinal temperature decay coefficient and the ratio of the distance from sidewall and tunnel width. Meanwhile, based on Hu?s model, a revised formula for predicting the dimensionless longitudinal temperature rise by considering the effect of transverse fire location is established.