Local characteristics of atmospheric dispersion within building arrays

Abstract

Dispersion of pollutants within building arrays was examined in the field, using model obstacles that represented real structures at a nominal scale between 1 10 and 1 20 . The main purpose of the experiments was to examine the local characteristics of flow and dispersion in the vicinity of individual obstacles embedded in an array of cuboid buildings. Two building array configurations were used, namely in-line and staggered. The spacing of the buildings in the array was S/ H=1.5 (where S is the space between two consecutive array elements). This spacing was chosen after a wind tunnel flow visualisation study of the effect of obstacle spacing on dispersion. Dispersion around isolated model buildings of similar shape and orientation to the mean wind direction has already been investigated in the field (Mavroidis et al., 2000, Atmospheric Environment, submitted for publication). A comparison is presented between dispersion around an isolated building and around the same building embedded in an array of cubes, which represented an urban area. The results suggest that enhanced mixing and dispersion occur within the array. Furthermore, differences in concentrations measured in the wake of obstacles of different shape and orientation with respect to the mean wind direction are reduced within the array, compared with the isolated obstacle case.