A hybrid Lagrangian-Eulerian particle model for reacting pollutant dispersion in non-homogeneous non-isotropic turbulence

Lagrangian stochastic models are recognized as being powerful tools for pollutant dispersion at different scales in complex terrain and at different stability conditions. One of the still unresolved problems is the difficulty of including chemical reactions when, for example, NO₂ or O₃ concentrations have to be predicted in the presence of NO_x emissions. In this work, a Lagrangian stochastic (single particle) model is modified in order to account for simple chemical reactions and tested against measured data in a wind tunnel. It is well-known that, in the single particle models the trajectories are considered independent and hence the concentration correlations and fluctuations cannot be calculated. However, these models can be simply modified to account for the segregation throughout a proper parameterisation derived from measurements. Further, in order to avoid the use of the large amount of computational resources, which would be necessary due to the release of an high number of particles filling the whole domain, needed to reproduce the ozone background concentration, we mark the particles with a deficit of ozone instead of its concentration. A numerical experiment is carried out and the results of the comparisons between calculated and measured concentrations of different species are presented and discussed.