Modelling of air pollution on urban buildings: a wind tunnel study

Tools for predicting where areas of high ingress of external pollution occur on a building can be developed if information regarding wind flow, dispersion and infiltration processes is available. These tools can be used for developing effective ventilation strategies for improving indoor air quality in urban buildings. In deriving them, it is important to determine the region from which pollution sources affect the building and generate concentrations on its surface. To this end, the effects of the position of external pollution sources on the magnitude and spatial variation of concentrations on a building model were investigated in a boundary layer wind tunnel. The tests were carried out at a nominal building model scale of 1: 100 and involved continuous releases of a tracer gas at different locations within generic arrays of buildings. The region of influence of sources around the test building was variable in shape and size depending on the area density of the building array and the incident wind direction. The region increased in size across the wind with increasing area density of the array and was progressively skewed in the direction of the approaching wind with progressive increments in wind angle. The spatial variation in concentrations on the test building decreased with increasing source distance from the building, with no apparent consistency between the different configurations. The region from which sources generated high variations in concentration on the test building extended a considerable distance upwind of the building in each array.