An examination of simple models for building influenced dispersion

A comparison is made between five simple theoretical models for building influenced dispersion and extensive experimental data for ground level concentrations. The models are all based on the Gaussian plume formulation and account for building effects by specifying enhanced dispersion parameters related to the building shape. Wind tunnel concentration data have been mainly used for testing the models because of its good quality and repeatability. The data have been chosen for a wide range of building shapes, with stack heights up to 1.5 times the building height and includes studies of detailed nuclear power station sites. The comparison shows that all the models give reasonable predictions of centreline ground level concentration for low level sources. For high level sources, the models with no allowance for stack height overpredict for normal orientations of the building with respect to the wind direction but are reasonable for diagonal orientations. Models which attempt to allow for variations in stack height tend to underpredict diagonal cases. The models predict plume spreads reasonably well, but cannot reproduce the non-Gaussian plume shapes or the behaviour with wind direction which are observed. (author)