Numerical Analysis of Particle Dispersion Characteristics at the Near Region of Vehicles in a Residential Underground Parking Lot

The study analyzed the transient air flow and particle dispersion at the near region of vehicles under idling conditions in an underground parking lot. It was found that the exhaust jet and particle dispersion behind the vehicles could be treated as a “nearly static” process from 20 seconds after the vehicle started. During the nearly static process, the particle dispersion behind the vehicle could be simplified to be exponentially upward. The particle concentration decreased logarithmically after 0.5 m behind the vehicle. The curvature of the particle streamline behind the vehicle under high exhaust temperature conditions is larger compared with that under low exhaust temperature conditions. When the vehicle exhaust temperature is high enough (318 K or higher in the study), the relationship between time and particle concentration above 3 m remains constant.