A field experiment on turbulent concentration fluctuations of an atmospheric tracer gas in the vicinity of a complex-shaped building

This work investigates the turbulent flow and dispersion of atmospheric contaminants in the vicinity of an isolated building. Field experiments were carried out to measure the fluctuating concentration time-series on the walls of a complex-shaped building, and to investigate the influence of atmospheric stability and building dimensions on certain statistics of the concentration distribution on the walls of the building. Meteorological conditions varied from neutral to unstable. The measurements were conducted for two different wind directions (west and south, corresponding respectively to directions normal and parallel to the long axis of the building). The experiments were performed in flat terrain with uncut vegetation. The gas detectors used were photo ionisation detectors (PIDs) with a response time of approximately 1/50 s. Sixteen such detectors were deployed, with 14 located on the building walls, and 2 on the roof. The analysis presented here is for the 14 detectors on the walls. Statistical parameters of the concentration time-series and the wind flow are presented, including mean and standard deviation. Intermittency and concentration fluctuation intensity are also presented. Results were analysed based on the turbulent structures of the fluid flow around the building. The experimental work revealed that the atmospheric stability conditions significantly influenced the concentration levels on the external walls of the building, except on the windward wall. It was also revealed that mean conditional concentration values on the walls were significantly influenced by the ratio between building width and height.