NUMERICAL SIMULATION OF AIR DISTRIBUTION AND INFLUENCE ON POLLUTANT DIFFUSION IN THE LONGITUDINAL VENTILATION OF AN URBAN TUNNEL WITH STEEP SLOPES

摘要

Using CFD technology, this paper set up a 3D model of an urban tunnel with steep slopes. As the accumulation of pollutant concentration will place a great effect on that at portal, this paper simulate the full tunnel. The mesh of each tunnel was made with about 6,989,062 triangular base prismatic cells. The simulated pollutant was CO. The results showed that the velocity distribution changes significantly at variable cross-sections. The pollutant diffusion is significantly affected by different slopes in tunnel. The concentration of CO accumulated when met slopes which created a great risk especially in the ascending line of 4.5% steep slope with opposite ventilation direction. The concentration of CO is highest at outlet, but still meets the domestic design standards. Appropriate reducing tunnel ventilation and increasing ventilation equipment investment are advised. A comprehensive consideration of feasibility and economical efficiency should be analyzed to give the best ventilation solution.