Coagulation of suspended particles by Brownian motion for the quasi-self-preserving case

An analytic solution is developed for the aerosol coagulation problem in the transition regime. The size distribution of a coagulating aerosol is represented by log-normal functions and particle size distribution is assumed to pass through a series of quasi-self-preserving size distributions. The effects of Knudsen number on the Brownian coagulation are discussed along with the results. It is confirmed that after a sufficient period of elapsed time, a self-preserving log-normal size distribution develops whose geometric standard deviation remains unchanged. Such a distribution is found to be narrower than that for the continuum regime and depends upon the Knudsen number. It is shown that the current model serves as the upper bound for the transition regime coagulation problem while the continuum regime constitutes the lower bound. Good agreement was obtained when the present analytic solution was compared with existing numerical studies on transition regime coagulation for the regime up to the Knudsen number of about 1.