A comprehensive numerical simulation of traffic pollution in a street during one diurnal cycle

A numerical simulation of the traffic pollutant transport diffusion within one busy street of Nantes city centre has been realized for a real-time dur ation of 24 hours, with a time step of 20 ms, in low wind, sunny conditions . It has been generated with the urban canopy model CHENSI, which includes sub-models of thermal buoyancy, traffic emission rates, car induced turbule nce. A number of frames of the simulation film are selected to illustrate t he mechanism and the influence of the coupling between dynamic and thermal convections upon the flow regimes, the street ventilation, the distribution of the pollutant concentrations and the pollutant residence times.