Physical Modelling of Flow and Diffusion in Urban Canopy

Dispersion of pollutants in urban areas is still challenging task in environmental sciences. Complex processes like the dispersion of accidental releases of harmful gas in built-up areas are not yet fully understood. For a better understanding of the phenomena it is helpful to study flow and dispersion within an idealised setting first. An example of a simplified setup at full scale is the Mock Urban Setting Test - MUST. In order to extend the field data set as well as to enhance the representativeness of the MUST field data a complementing study in a boundary layer wind tunnel was carried out. During an extensive measurement campaign in the wind tunnel firstly flow field, including turbulent characteristics, was studied for different wind directions. The second step was replication of field dispersion experiments. Travelling time of the pollutant was estimated by three different methods: (i) spatial concentration correlations function; (ii) the time delay of a sudden released tracer at a detector position; (iii) the time based on the measured wind speed along the tracer trajectory. All three methods showed comparable results.