Simulation of Brownian Coagulation in the Presence of van der Waals Forces and Viscous Interactions

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Abstract
Coagulation of aerosol particles in the size range of 0.001–10 μm in particle aerodynamic diameter is simulated by using a model based on a sectional representation of the aerosol size distribution. The influence of van der Waals forces and viscous interactions are both incorporated, and this interaction enhanced coagulation is compared with coagulation resulting from pure Brownian movement. The interparticle van der Waals potential applied in calculations is based partially on Hamaker's theory and partially on the limiting approximations to the equations of Langbein. Viscous interactions are incorporated by using a corrected form of the particle binary diffusion coefficient. As expected, coagulation between ultrafine particles was clearly enhanced due to the interactions. No essential differences between Brownian and interaction influenced coagulation was to be seen above 0.05 μm of particle diameter or between particles located in separate size modes.