Dispersion of traffic emissions around tunnel portals

Abstract: The accumulation of vehicle emissions over the length of a tunnel may lead to pollutant concentrations around the portals exceeding the threshold values - especially in an urban environment. This paper will describe how CFD-simulations can be used to give a detailed insight into the dispersion and dilution of traffic-related pollutants accounting for multiple wind directions and speed. Buildings and possible vegetation in the target area can be modelled in 3D and included in the simulations. Based on these simulations, the development plans for areas around tunnel air exhausts may be modified – or alternatively the location and design of air exhausts can be adjusted.