Penthouses’ impact on the wind flow structure and pollution distribution in the street canyons with or without balconies on building facades

This research is focused on how the different shape and parts (penthouses balconies, etc.) of a building with an aspect ratio of 2.33 takes part firstly to the creation of the flow field around it and secondly to the distribution of pollutants concentration. For the simulation a Computational Fluid Dynamic package (ANSYS-FLUENT) was used. The closure of the dynamic flow equations employed the steady state κ - ε RNG (Re-Normalized Group theory) method. In order to achieve a good compromise between accuracy and computational time, the flow domain was divided into 2 regions, each with its own grid. The street canyon (height = 28 m, width = 12 m) incorporated a finer structured Quad (Cartesian) grid of uniform spacing whereas for the remaining domain (above the canyon) incorporated a coarser structured mesh of tetrahedral elements. Numerical results illustrate the formation of the vortices (i.e. number, nature, rotation rate) inside the canyon and the vertical concentration profiles of the aerosol particles. It is demonstrated that the presence of the penthouses helps the pollutant to escape from the cavity. The vorticity patterns are more complex for the penthouse scenarios compared to the scenarios without them showing more turbulence and mixing.