Wind tunnel experiments for flow and pollutant dispersion in turbulent boundary layer over urban areas

Abstract

Wind flow and pollutant transport in the atmospheric boundary layer (ABL) over urban areas are strongly affected by the dense buildings at land surface. Characterising the flow structure and pollutant plume dispersion over different urban morphology is important because it elucidates the mechanism of shear-induced turbulent pollutant transport processes. Series of wind tunnel experiments were performed in this study to investigate the flow and pollutant dispersion over two-dimensional idealised street canyons with different aspect ratios (buildingheight-to-street-width). Streamwise and wall-normal velocities were obtained by using hot-wire anemometry (HWA) with X-probe design. Simultaneously, using moisture as a passive scalar, the concentration profiles were measured after a line source emission from ground surface. Vertical profiles of mean wind, turbulence and scalar concentration were analysed in attempt to develop practical parameterizations for the flow and dispersion. Future work will be focused on the measurement of flows and scalar distribution over reduced-scale urban morphology models fabricated by 3D printing technique.