Estimating longitudinal maximum smoke temperature attenuation due to large-angle bifurcation in UTLT-like tunnels under longitudinal ventilation condition

Abstract

Extensive studies have focused on single-straight tunnels or subway bifurcation tunnel fire. However, the effect of large angle bifurcation on longitudinal maximum temperature rise attenuation in Urban Traffic Link Tunnel（UTLT）needs to be further studied. In this study, based on the theoretical analysis, a double exponential prediction model for longitudinal temperature rise attenuation in bifurcation tunnels is established. To obtain the correlation coefficients, a series of full-scale numerical fire simulation experiments were carried out in an UTLT-like tunnels using Fire Dynamics Simulator. The results revealed that the bifurcation structure of the large-angle bifurcation angle tunnels impeded the longitudinal movement of the fire smoke and hot smoke diversion. Without longitudinal ventilation conditions, the longitudinal decay of the temperature rise in each region can be expressed as the sum of double exponential expressions with different coefficients. The law governing the effect of the bifurcation angle on the longitudinal decay of the temperature rise is the quadratic equation of the angle sin α. A prediction model for the longitudinal decay of the temperature rise in the tunnel downstream of the fire source under longitudinal ventilation is proposed. The findings of the numerical simulation corresponded to those of the model prediction.