Particles emitted from vehicles can threaten human health. Therefore the investigations about the particle dispersion characteristics inside the street canyon are of significance. For the current work, the airflow fields and the particle movement inside an isolated street canyon with three aspect ratios under perpendicular wind direction and two typical wind speeds are studied numerically, for which the particle distributions are obtained by solving the drift-flux model. The conclusions demonstrate that the trees will result in the particles gathering. However, the particle deposition fluxes on the trees are so small which cannot effectively remove the particles from the ambient air. Besides, the vehicles tend to cluster particles around the street axis and slow down the dispersion to the curbside buildings. Therefore, the vehicles should not be ignored in the numerical models, especially for the cases in the wind direction of 90°. Moreover the cases with the aspect ratio of 0.5 are more sensitive to the effects of trees and vehicles. The shop vendors expose to the highest particle concentrations in most of the scenarios.

Air cleaners are expected to improve the indoor air quality by removing the gaseous contaminants and fine particles. In our former work, the effects of the air cleaner on removing the uniformly distributed particles were numerically investigated. Based on those results, this work further explores the performances of the air cleaner in the reduction of two nonuniform particle distributions generated by smoking and coughing. The Lagrangian discrete trajectory model combined with the Eulerian fluid method is employed to simulate the airflow pattern and particle transport in a room. In general, the results show that the particle fates have been resulted from the interaction between the emitting source and the air cleaner. And the position of the air cleaner is a key parameter affecting the particle concentration, for which a shorter distance between the air cleaner and the human body corresponds to a lower concentration. Besides, the air velocity emitted from the human mouth and the orientation of the air cleaner can also influence the transport of particles.

Single-sided natural ventilation has been common in multi-family residential buildings. Current research usually presumes that the outdoor air is clean, which is not realistic under the outdoor pollution situations. In this study, the particle transport and airflow pattern in an isolated living room with the single-sided natural ventilation are numerically investigated by means of Eulerian drift-flux model combined with the Eulerian fluid method. The results indicate that larger wind speed does not necessarily achieve better ventilation effect and higher air change rate (ACH). At high wind speeds, the effect of wind direction on the room average concentration becomes more conspicuous. Small particles tend to disperse in the room more uniformly while large particles exhibit stratified distributions. The results would be useful for optimizing single-sided natural ventilation in buildings.