Experimental investigation of smoke temperature and movement characteristics in tunnel fires with canyon cross wind

Abstract

A series of tests were conducted in a model-scale tunnel to investigate the influence of canyon cross wind on smoke temperature and movement characteristics of tunnel fires, including temperature distribution below ceiling, smoke back-layering length, and smoke stratification characteristics. Canyon cross wind speed, pool size, and fire location were considered. Experimental results show that the temperature along tunnel ceiling decays exponentially, but the variation laws of the upstream and downstream temperature decay coefficients are different with the increasing canyon cross wind speed. The dimensionless confinement velocity is defined as the ratio of the canyon cross wind speed to the critical velocity, and the relationship between the dimensionless smoke back-layering length and the dimensionless confinement velocity is obtained. The state of the smoke stratification is related to the canyon cross wind speed and the fire source location. When the fire source is subject to a relatively strong canyon cross wind or closer to the upstream tunnel portal, the smoke stratification will become more unstable. The results can provide engineering reference for smoke control and safe evacuation of mountain tunnels.