Numerical study on the vehicle exhaust dispersion in a curved tunnel: Effects of the tunnel radius and tilt angle of jet fan

In the present work, computational fluid dynamics (CFD) was used to study the dispersion behaviours of vehicle exhaust, including the CO and PM in a curved tunnel with a consideration of the coupling effects of tunnel radius and tilt angle of jet fan. The simulation results showed the variations in the high-speed jet area in the tunnel under different tunnel radii and tilt angles of jet fan. For the pollutant diffusion, concentrations of CO and PM were shown to be inversely proportional to the tilt angle of jet fan and tunnel radius. In the vertical direction, the PM concentration was not always decreased with the increase in the altitude, which is different from distribution of CO concentration. In the horizontal direction, CO was mainly distributed at 20 – 60 m downstream from the fan, while PM accumulation covered the entire downstream of the tunnel. A close relationship between the distribution of pollutant concentration and vortex structures was found. The present work could contribute to knowledge for reducing the energy consumption of jet fans and the pollutant concentration in the curved tunnel and would provide significant guidance for the future design of curved road tunnels.