Wind-induced dispersion of pollutants in the urban environment

Abstract

Predicting air and pollutant flow around buildings in an urban environment is a very complex problem affecting building design and performance. This chapter presents some of the new developments in this field, as far as the assessment of pollutant concentrations is concerned and the evolving design guidelines in this area. Particular emphasis is placed on the results of wind tunnel studies to assess the influence of adjacent buildings and rooftop structures on near-field pollutant dispersion by considering various parameters, such as stack height, exhaust momentum and spacing between buildings. A general discussion of the various ASHRAE models, as well as comparisons with wind tunnel results for a few adjacent building configurations, is presented. Application of ADMS, a Gaussian-based dispersion model, on near-field pollutant dispersion is also discussed. Comparisons for computational fluid dynamics (CFD) results and wind tunnel data for a particular case are made. The limitations of ASHRAE and CFD models to predict realistic dilutions for particular building configurations, besides suggestions to improve them, are discussed. Guidelines regarding appropriate stack and intake locations to avoid plume reingestion are also presented.