Professor Alan Robins

Wind tunnel experiments on regular arrays of buildings were conducted in the environmental wind tunnel in the EnFlo laboratory at the University of Surrey. The model canopy comprised a square array of 14×21 rectangular blocks (1h × 2h) with height h = 70 mm. Preliminary measurements of velocity, turbulence and tracer concentrations were made for 3 wind directions: 0, 45 and 90◦. The results from this first experimental campaign along with numerical simulations have shown that the canopy has obstacles sufficiently long compared with their heights to yield extensive flow channelling along streets. Across the whole of the downwind half of the long street the flow for the present canopy is closely aligned with the obstacle faces, despite the 45◦ flow orientation aloft. This supports the suggestion that the streets are long enough to be representative for street network modelling approaches; shorter streets would probably not be sufficient and it will be interesting to see how well network models can predict concentrations in the present canopy. The extensive array and the small scale of the model posed challenging problems for reaching the desired high accuracy needed to validate the numerical simulations. The improvements in the methodology will be presented and discussed at the conference. The wind tunnel data, along with LES and DNS simulations, are being used to understand the behaviour of flow and dispersion within regular array with a more realistic geometry than the usual cuboids. This integrated methodology will help developing parametrisations for improved street network dispersion models