Brownian coagulation of like-charged aerosol particles

In this paper, we study the coagulation rate of like-charged Brownian spherical particles dispersed in a gaseous medium. Most previous calculations of the Brownian-induced coagulation rate have considered that the particle pairs interact through continuum hydrodynamics, and at a close approach, van der Waals attraction forces allow the collision and subsequent coagulation. However, the continuum approximation of the hydrodynamic interactions is no longer valid when the gap thickness between the surface is less than the mean free path of the surrounding fluid medium and the noncontinuum lubrication interactions lead to surface-to-surface contact in a finite time. We report the Brownian coagulation rate in the presence of noncontinuum lubrication resistances for a range of pair size ratios. At small separations, like-charged conducting particles almost always attract each other. Thus we also incorporate the attractive electrostatic interactions between like-charged conducting spheres in our calculation and report the effects of van der Waals and electrostatic forces on the coagulation rate of conducting spheres interacting with each other through noncontinuum hydrodynamics for a range of size and charge ratios.