Numerical Study of Particle Distribution in the Wake of Particle-Laden Airflows past a Group of Four Rectangular Buildings Using Discrete Vortex Method

A numerical investigation is conducted on particle distribution in the wake of dilute particle-laden airflows past a group of four rectangular buildings at Reynolds number of 10,000,000. In the numerical method, the Discrete Vortex Method is employed to calculate the unsteady airflow fields and a Lagrangian approach is applied for tracking individual solid particles. A dispersion function is adopted to represent the dispersion scale of particles. The vortex patterns and the distributions of particles with Stokes numbers, St, of 0.01, 0.1, 1.0 and 10 are obtained. The numerical results show that the particle distribution around the four rectangular buildings is closely related to the particle´s Stokes number and the structure of vortices: (1) very small sized particles with St=0.01 can distribute both in the vortex core and around the vortex periphery, whereas the intermediate sized particles with St=1.0 can not enter the vortex core and concentrate near the vortex periphery; (2) particles with St=0.01 are evenly distributed in the whole gap area between the buildings, whereas the particles with St=1.0 can hardly enter the gap area along the transversal lane and concentrate around the center of gap area along the longitudinal lane; (3) the dispersion intensity of particle decreases greatly as St increases from 0.01 to 10. This work will be helpful in predicting and analyzing particle pollution levels around a group of rectangular buildings.