Flow and dispersion near clusters of buildings

A brief summary of the flow patterns expected near isolated simple buildings is reviewed. Flow patterns associated with varying densities of uniformly sized buildings in an extensive array are then discussed. A systematic study of near-ground-level flow patterns within simple building clusters is summarized. The suite of presently available models for estimating near-building and wake concentrations is briefly described. It appears to be possible to arrive at rough concentration estimates close to buildings only in cases where one building of a cluster is dominant in size, or within an extensive array of similarly-sized structures. The recent literature suggests that several models developed for single-building intermediate and far wake concentration estimates are also useful for building clusters; the appropriate model depends on whether the effluent source is in the near wake region at ground level, or is a roof-mounted vent, or is a roof-mounted stack of typically modest size. Problems associated with very wide buildings and with cases when the wind approaches at an angle to the buildings are described, and some possible remedial steps are suggested. Additional work is needed in several areas to improve present understanding and to provide better guidance to the practitioner; research recommendations are therefore included.