On modeling and simulations of photochemical smog formation in simplified and complex urban areas

摘要

In the present study we address numerical modeling and simulations of flow, turbulence and reactive pollutant distributions (smog formation) within and over simplified (laboratory scale) and complex (real scale) urban areas. We have extended the recently proposed seamless hybrid T-RANS/VLES approach ([1], [2]) with additional set of the reactive scalars, to represent chemistry of the photochemical smog formation. The smog is generated as a result of a chemical reaction of nitrogen oxides and volatile organic compounds in atmosphere, which is triggered by sunlight. The presence of nitrogen oxides is caused by traffic or industrial emissions. We demonstrate that application of the Generic Reaction Set (GRS) model represents a good compromise between the physical accuracy, numerical efficiency and robustness in predicting smog formation. The model is validated first by comparisons with experiments for a reactive plume dispersion in decaying turbulence where good results are obtained in predicting radial profiles of NO, NO_2 and O_3 at different locations behind the point emission source, proving correct modeling of the chemistry. Then, we test combined effects of flow recirculation and different exposure to the sunlight within a laboratory-scale street canyons. The GRS model predicted local ozone distributions in good agreement with observations. Finally, a real-scale environmental applications (one of neighborhoods in city of Rotterdam, The Netherlands) is presented for typical approaching wind conditions and localized pollution emissions from the main roads.