Prediction of the pollutant diffusion discharged from wind tower of the city traffic tunnel

• Pollutant diffusion discharged from wind tower of city traffic tunnel was studied.
• Pollutant concentrations of CFD simulation agrees well with wind tunnel test.
• Four distances and three height differences of wind tower and building are studied.
• C/C0 is negligible for the bottom of the building and relatively high for the top.
• The pollutant concentration on the windward side is greater for higher building.

With the increase of the urban traffic volume, a large number of tunnels have been built in many cities; the vehicle emission from the traffic tunnel has a significant impact on the surrounding environment, it has important meaning to study the impact of pollutant diffusion discharged from wind tower on the downwind environment, and to evaluate the air pollution situation and variation tendency around the wind tower. In this study, a reduced scale model of 1:200 is used for three-dimensional numerical simulation and wind tunnel test; results show that the numerical simulation result agrees well with the result of the wind tunnel test. The diffusion of pollutant discharged from the wind tower with the actual size is simulated by the computational fluid dynamics (CFD) program; results show that, the CO concentration ratios of points on building windward side to that of the wind tower outlet (C/C0) are reduced to 1.211%–1.563% on the middle vertical line of building windward side at a distance of 200 m when the building is 39 m (10 m higher than the wind tower), 0.974%–1.215% when the heights of the building and the wind tower are both 29 m, and 0.654%–0.834% when the building is 19 m. When C/C0 of building windward is lower than the maximum allowable value of 2.67%, the required shortest distances between the building and the wind tower are 50, 150 and 200 m for the building heights of 19, 29 and 39 m, respectively. The results can be a reference for the design of wind tower of traffic tunnel and the determinations of the location and height of downwind new building.