STUDY OF ATMOSPHERIC DISPERSION UNDER LOW WIND CONDITIONS IN AN URBAN ENVIRONMENT, FIRST RESULTS

All atmospheric conditions must be considered in the impact calculation of industrial facilities. In low wind conditions (wind speed below 2m.s^-1), the meandering (low frequency horizontal wind oscillation) becomes one of the predominant physical processes which drive atmospheric dispersion of pollutants. Experimentally, it can be identified by analyzing the autocorrelation function of the horizontal wind speed components. However, modeling these situations is more complicated, and most models are unable to correctly reproduce the turbulent flow structure and the resulting plume dispersion. The CFD models could overcome these limits by adapting the existing modeling approaches to low wind speed situations. In this study, we present the first analyses of datasets from an experimental campaign that has been performed at SIRTA in the south of Paris in 2020 as well as first simulation results obtained with a CFD model using two different modelling approaches: stationary and pseudo stationary conditions. The analysis of wind data acquired during one selected time period of the campaign allowed to identify the presence of meandering and to estimate its period. Compared to concentration measurements, the first modelling approach seems to lower lateral dispersion while the second approach seems to give closer results.