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 inve stigate the dispersion of a tracer gas emitted from a ground level source o n 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 o f pedestrian level locations around the model using fast-response flame ion isation detectors. These were supplemented by pedestrian level wind speed m easurements using hot-film anemometry. Measurements were made for changes i n the wind azimuth angle and for changes to the building geometry. General conclusions were drawn about the relationships between building geometry an d the pedestrian level atmospheric environment and a number of simple empir ical relationships derived between the changes in the measured wind charact eristics and the characteristics of tracer concentration. loot. mean and fl uctuating wind speeds and concentrations were measured In the experiments a nd subsequently quantified using a novel empirical method that may potentia lly be of use to both urban planners and wind tunnel engineers. (C) 1999 El sevier Science Ltd. All rights reserved.