14. A New Approach to Building Downwash Modelling

Thompson (1991, 1993) measured ground-level concentrations profiles (GLCPs) for 330 combinations of stack height, building type and distance between stack and building. Cosemans and Lefebvre (Dispersion parameters in a wind tunnel and in the field: analysing Thompson’s 1991 wind tunnel data for isolated stacks with IFDM, and its application to building downwash. In: Preprints of the 13th international conference on harmonisation within atmospheric dispersion for regulatory purposes, Paris, pp 304–308, 2010) derived dispersion parameters needed by the bi-Gaussian transport and dispersion equation to reproduce the GLCPs measured for nine isolated stacks. Now, we present a formula to reproduce the 321 other GLCPs, measured. Basically, the plume affected by building downwash is replaced by a set of plumes that have a modified lognormal distribution of height and pollutant mass. The different phenomena that influence plume growth subject to building downwash are modelled by virtual origin functions. Incorporating this in a regulatory plume model could strongly increase the capacity of such model to predict the pollutant concentrations in the vicinity of buildings neighbouring emission sources