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Abstract and Applied Analysis
Volume 2013 (2013), Article ID 709497, 7 pages
http://dx.doi.org/10.1155/2013/709497
Research Article

Evolution of Aerosol Particles in the Rainfall Process via Method of Moments

School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China

Received 20 July 2013; Accepted 13 August 2013

Academic Editor: Jianzhong Lin

Copyright © 2013 Fangyang Yuan and Fujun Gan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The method of moments is employed to predict the evolution of aerosol particles in the rainfall process. To describe the dynamic properties of particle size distribution, the population balance equation is converted to moment equations by the method of moments and the converted equations are solved numerically. The variations of particle number concentration, geometric mean diameter, and geometric standard deviation are given in the cases that the Brownian diffusion and inertial impaction of particles dominate, respectively. The effects of raindrop size distribution on particle size distribution are analyzed in nine cases. The results show that the particle number concentration decreases as time goes by, and particles dominated by Brownian diffusion are removed more significantly. The particle number concentration decreases much more rapidly when particle geometric mean diameter is smaller, and the particle size distribution tends to be monodisperse. For the same water content, the raindrops with small geometric mean diameters can remove particles with much higher efficiency than those with large geometric mean diameters. Particles in the “Greenfield gap” are relatively difficult to scavenge, and a new method is needed to remove it from the air.