Large eddy simulation for improving smoke extraction efficiency by inverted V‐shaped baffle in the urban tunnel

Abstract

Summary In order to reduce the undesirable effect of boundary layer separation and plug‐holing in a naturally ventilated tunnel with shaft for smoke extraction, a new design of baffle has been proposed in this paper. Large eddy simulation (LES) was performed with fire dynamics simulator (FDS), the influence of the angle formed by the boards (θ) and the distance between the baffle top and the shaft bottom (d) has been investigated. The simulation results show that the smoke extraction efficiency is not simply a monotonic function of the distance d or the angle θ, the influence of d and θ has been discussed, and the mechanism has been investigated. With proper configuration of the inverted V‐shaped baffle, the negative effect of plug‐holing can be eliminated, and the boundary layer separation can also be alleviated; the maximal smoke extraction efficiency is 2.04 times of that in the traditional shaft.