Considering the semi-transverse exhaust ventilation of a certain city tunnel

the ventilation hole was made in the upper left wall in the tunnel.We established an 1:1 three-dimensional simulation model by using the computational fluid dynamics numerical simulation method and simulated wind speed

air pressure and the concentration of pollutants in the tunnel in different conditions and made different shapes of ventilation holes

and then carried out the comparative analysis

and drew some conclusions:in the tunnel cross section with ventilation hole

a "exhaust section" is formed

for which high negative pressure and large pressure gradient are in left region and small negative pressure is in right region;With the increasing height of ventilation hole

the distribution of negative pressure expends to the right of the exhaust section and the wind speed increaes in the right region and is helpful to the dilution of pollutants in the right region

but the vertical wind speed reduces and the direction of flow is disordered in lower left region that makes the concentration of pollutants greater in left region.