Dispersion of traffic exhausts in urban street canyons with tree plantings : experimental and numerical investigations

Wind tunnel experiments and numerical computations have been performed in order to investigate the influence of avenuelike tree plantings on the dispersion of traffic exhaust in an urban street canyon. Reduced natural ventilation and enhanced pollutant concentrations have been found in the presence of trees. A comparison of experimental and numerical results shows qualitative good, but quantitative rather poor agreement. In the numerical computations, flow velocities are underestimated and pollutant concentrations are overestimated