Brownian coalescence frequency

In obtaining the Brownian coalescence frequency, we had assumed that particles move independently of one another even when they are in the immediate proximity of each other. Thus, the foregoing analysis does not account for any correlation between the movement of particles as a result of interparticle forces and/or viscous forces in the intervening fluid. We next outline the manner in which such effects may be included in the derivation of the aggregation frequency. 

Aerosols are unstable with respect to coagulation. The reduction in surface area that accompanie.s coalescence corresponds to a reduction in the Gibbs free energy under conditions of constant temperature and pressure. The prediction of aerosol coagulation rates is a two-step process. The first is the derivation of a mathematical expression that keeps count of particle collisions as a function of particle size it incorporates a general expression for tlie collision frequency function. An expression for the collision frequency based on a physical model is then introduced into the equation Chat keep.s count of collisions. The collision mechanisms include Brownian motion, laminar shear, and turbulence. There may be interacting force fields between the particles. The processes are basically nonlinear, and this lead.s to formidable difficulties in the mathematical theory. 

---