The research will involve wind-tunnel experiments on modelling flow and dispersion of gaseous pollutants inside and around urban street canyons, street intersections, and urban canopy clusters with streets. Direct co-operation with U.Hamburg is expected. Parallel numerical studies of wind-tunnel cases in co-operation with the ECN group, and comparisons with the full-scale measurement data from ETHZ are also planned.
Mean flow and turbulence measurements will be performed with laser Doppler velocimeter, and with the aid of laser-sheet visualisation technique. Traffic pollution will be simulated by near-surface linear sources stretched along the streets. Measurements of concentration mean fields, fluctuations, and turbulent fluxes of pollutant are anticipated. Influence of surrounding buildings, source position, building and roof shape, approaching flow parameters (direction, flow-profile shape, turbulence level), street-canyon geometry (aspect and length-to-width ratios, spatial inhomogeneity) on the flow and pollutant concentration patterns inside and above the canopy layer will be studied.
The particular points of interest will be:
The other research topic will focus on the modification of flow and concentration fields in streets (street canyons) by moving vehicles. The experiments will be performed in the atmospheric boundary-layer wind tunnel. The simulation methodology will be elaborated, and experimental data will be analysed in co-operation with NERI.
Technique for simulating moving vehicles in the wind-tunnel model of an urban street will be designed and tested. Scaling relationships for physical modelling of the vehicle induced turbulence will be verified. The conceptual framework for comparison of wind-tunnel model results with data of field experiments and numerical models will be developed. Numerical parameterisations of vehicle induced turbulence will be evaluated.
Detailed measurements of turbulence parameters under different flow conditions inside and around the canyon will be carried out by means of laser Doppler technique. Effects of moving vehicles on mean concentration fields, and on the parameters of pollutant transport inside a street canyon will be studied. Approaches towards physical modelling of pollutant dispersion in street canyons with traffic under low wind conditions, when thermally induced motions play an important role in pollutant transport, will be investigated.