Dispersion from elevated sources above obstacle arrays: modelling requirements

Abstract

A series of wind-tunnel experiments is used to investigate the requirements of practical models for the prediction of the behaviour of stack emissions from an industrial site (i.e. a group of buildings), in particular for the determination of ground-level concentration or exposure downwind from the site. The study addresses Gaussian plume modelling and, assuming that an adequate model exists for treating the emission in the absence of complicating site features, considers the questions: a) How should the model be modified to account for the influence of the site? b) Which of these modifications is most important? c) How can a group of site buildings be replaced by an building? Realistic modelling of plume height reduction (building induced downwash) is shown to be the key to the successful prediction of the dispersion of elevated emissions above obstacle arrays (in this case, for h/H 3 ≥ 1.2, where h is the source height and H the building height). Some simple rules are defined for representing an array by an effective obstacle.