On the wind flow patterns under neutral and unstable conditions in an urban area

Wind flow and pollutant dispersion within urban areas depend on the approaching flow profile and temperature stratification. Thus, the flow field developed under neutral and unstable stratification conditions, within a street-canyon, was studied experimentally and numerically for a two-dimensional urban background set-up. Wind-tunnel measurements were carried out with a triple hot sensor anemometer, while an academically developed CFD κ-ε algorithm was applied, employing an unstructured Cartesian grid. The numerical code compared well with experimental results. Under unstable conditions, intensive mixing exists within the street-canyons and the buoyancy-induced flow affects the vertical air motions within and above them.