Wind tunnel tests on the dispersion of vehicular pollutants in an urban area

Results are presented from an extensive series of wind tunnel tests to investigate the dispersion of a tracer gas emitted from a ground level source on a 1:125th scale model of an urban area typical of those found in the UK. Concentrations of a tracer gas, propane in air, were measured at a number of pedestrian level locations around the model using fast-response flame ionisation detectors. These were supplemented by pedestrian level wind speed measurements using hot-film anemometry. Measurements were made for changes in the wind azimuth angle and for changes to the building geometry. General conclusions were drawn about the relationships between building geometry and the pedestrian level atmospheric environment and a number of simple empirical relationships derived between the changes in the measured wind characteristics and the characteristics of tracer concentration. loot. mean and fluctuating wind speeds and concentrations were measured In the experiments and subsequently quantified using a novel empirical method that may potentially be of use to both urban planners and wind tunnel engineers. (C) 1999 Elsevier Science Ltd. All rights reserved.