Some field experiments on the interaction of plumes from two sources

Some experiments to measure concentration fluctuations downwind of two trac er sources in the atmospheric surface layer are described and the results p resented. Fast response detectors were used. The sources were at a height o f 4 m and the experiments were restricted to short ranges where the how and turbulence can be assumed to be approximately homogeneous for the purpose of predicting the dispersion. The results are analysed to show the downwind evolution of the intensity of fluctuations for each source separately and to show how the correlation between the concentrations from the two sources varies with downwind distance and source separation. The variation of the intensity of fluctuations and the correlation with averaging time is also e xplored. Results support the idea of a universal behaviour when suitably sc aled.