Numerical study of particle distribution in the wake of particle-laden air flows past a rectangular building using discrete vortex method

A numerical investigation on particle distribution in the wake of particle-laden airflows past a rectangular building at Reynolds number of 10(7) is presented. The Discrete Vortex Method is employed to evaluate the unsteady airflow fields and a Lagrangian approach is applied for tracking individual solid particles. A dispersion function is defined to represent the dispersion scale of the particle. The wake vortex patterns and the distributions of particles with Stokes numbers, St, of 0.01, 0.1, 1.0 and 10 are obtained. The results show that the particle distribution in the wake of the rectangular building is closely related to the particle's Stokes number and the structure of wake vortices: (1) very small sized particles with St = 0.01 behave like gas elements and can distribute both in the vortex core and around the vortex periphery, whereas the intermediate sized particles with St = 1.0, 10 can not enter the vortex cores and concentrate near the peripheries of the vortex structures due to the centrifugal forces acting on the particles by the wake vortices; (2) the dispersion intensity of particle decreases as St increases from 0.01 to 10. This work will be helpful in predicting and analyzing particle concentrations around rectangular buildings.