A unified theory of aerosol coagulation

Abstract

A unified theory of the coagulation of aerosols is presented based upon the solution of a generalised diffusion equation which describes classical diffusion due to Brownian and turbulent motion as well as the effect of an overall relative velocity arising, for example, from gravitational settling and inertial turbulent motion. Certain statistical assumptions regarding the turbulent motion enable exact solutions of the diffusion equation to be obtained for the four mechanisms mentioned above. As a result, the authors can assess the accuracy of the usual procedure of adding the coagulation kernel. It is also possible to include the effects of inter-particle fluid forces which result in a collision efficiency less than unity. In contrast to previous work on this subject, the collision efficiency affects all processes and not just gravitational settling. Significant deviations from the classically computed coagulation kernels are noted.