Asymptotic Behavior Of Size Distribution Of Aerosol Particles Undergoing Self-preserving Coagulation

As is known to us,the air to human is just like the sun to the flowers.With stepping up urbanization in China,Atmospheric aerosol pollution is pushed to the front of mankind,which is caused by the combustion emissions of the energy structure and the exhaust of the motor vehicle.Sulfur dioxide,Nitrogen oxides,Ammonia and other pollutants will form atmospheric aerosol particles in the appropriate atmospheric conditions.The environmental problems such as haze will appear,affecting the climate,atmospheric visibility,human health and so on.The influence of aerosol particle depends on the size distribution.Coagulation is the most important physical process of the aerosol particles.All contents of this article center on the coagulation of aerosol particles and it can be divided into two parts:one is about the theory of efficiency of aerosol coagulation in different regimes;the other is about the numerical methods for coagulation kinetics.Considering fractal dimension and the mechanism betxween Brownian Motion and Fluid Shear,MATLAB software is used to simulate the coagulation dynamics equation,which is divided into 30 by section method.It is necessary to analysis the evolution of self-preserving size distribution of the coagulation of the aerosol particles.The results show that the spherical or fractal aerosol aggregates undergoing single Brownian Motion or complex of Brownian Motion and Fluid Shear will present the self-preserving size distribution after a period of time.In this process,fractal dimension and particle collision mechanism have significant effect in coagulation.The fractal dimension determined the spatial structure of the aerosol aggregates.The smaller the fractal dimension is,the more open the aerosol aggregates are,resulting in a larger collision area and shortening the time-lag to reach self-preserving size distribution.The particle collision mechanism control the collision frequency function of the particles,the higher collision frequency causes the particles to collide quickly through the aggregation.In addition,a value exist in the coagulation undergoing Brownian Motion and Fluid Shear.When the situation of the flow field below this value,the Brownian Motion is dominant in the particle collision mechanism.Conversely,the Fluid Shear is dominantly.