Pollutant Diffusion and the Length of Mid-Partition Wall of Twin Portals for Large Cross Section Underwater Tunnel

In order to reduce the secondary pollutant rate (SPR) caused by pollutant cross flow at the portal of the double-hole tunnel, the k-ε cross flow model and the component transfer equations were used to numerically simulate the different portals and exits of the tunnel hole section by means of the CFD software Fluent. The wind velocity, the diffusion of pollutants under different natural wind conditions, and the study on the length of the mid-partition wall of tunnel portal. The research shows that when there is no natural wind, the SPR increases (decreases) with the increase of the inlet (exhaust) wind velocity. When the length of the mid-partition wall is set to 25 m, the SPR is less than 10%, which meets the requirements for CO to prevent channeling; When there is natural wind, when the inlet and exhaust wind velocity is given, the SPR increases with the increase of natural wind velocity, and the length of mid-partition is set to 40 m, the SPR is less than 10%. Therefore, it is recommended to set the length of the mid-partition wall of Taihu tunnel to 50 m. Research results can provide design reference for the length of the mid-partition wall of the large cross tunnel.