Investigation of the Flow Structure around Step-Up, Step-Down, Deep Canyon and Isolated Tall Building Configurations using Wind-Tunnel PIV Measurements

Extensive sets of detailed mean flow measurements were taken around idealized building configurations in a wind-tunnel simulated atmospheric boundary layer. This study is aimed at providing empirical guidance for dispersion modeling in urban environments. To this end, four different experiments were performed in which the geometric parameters of rectangular buildings were varied systematically. The first set of experiments involved the study of flow over an isolated tall building of different widths. This experiment was done to characterize the behavior of the mean flow streamlines in the lee of the tall building as a function of the building width. The second set of experiments were conducted for step-up street canyons of different building heights and widths. A step-up street canyon is defined as a street canyon in which the height of the upwind building is less than the height of the downwind building. The third set of experiments were for step-down street canyons of different building heights and widths. A step-down street canyon has a taller upwind building. The final set of experiments dealt with the flow structure in deep canyons of different building widths, but equal heights. The four experiments revealed many new and counter-intuitive flow patterns, including for the deep canyon case the displacement of the primary vortex in the canyon towards the downwind building as the building width was increased and for the step-up canyon case the formation of a secondary vortex within the street canyon as the building width increased. At the conference, the mean flow patterns as a function of building width and height will be discussed. This data set will be useful in evaluation of computational fluid dynamics codes and simpler building-aware transport and dispersion models.