Numerical study on the thermal buoyant flow stratification in tunnel fires with longitudinal imposed airflow: Effect of an upstream blockage

Abstract

Abstract This paper is focused on the thermal buoyant flow stratification, generated by fire that occurred in a tunnel congested by an obstacle simulating a vehicle. The obstacle occupies about 0.31% of the tunnel cross section and is located at different distances from the floor. This case is considered for two main reasons: the first is that the remaining vehicles blocked upstream of the heat source cause a partial obstruction, the second reason is that the vehicle bottom actually has a certain distance from the tunnel floor. The obtained results showed that the increase of the forced airflow velocity has for results a loss of stratification. The obstruction existence effect in tunnel is reflected by smoke flow destratification upstream of the heat source fire. However, this effect is compensated downstream of the fire and there has been an improvement in the smoke flow stratification contrary to the case where the tunnel would be empty.