KINETIC THEORY OF SHEAR COAGULATION FOR PARTICLES IN A VISCOUS FLUID

Abstract

The coagulation of colloidal particles in a simple shear flow of a viscous fluid is considered. The coagulation rate between unequal spherical particles is calculated by use of approximate trajectory equations, and a kinetic equation of shear coagulation is proposed in which the hydrodynamic interaction between particles is taken into account. It is found that the coagulation rate decreases rapidly with increase of the ratio of particles radius a_i/a_j and a dimensionless quantity 6πμa³_ijγ/A. Comparison between the present theory and the classical Smoluchowski theory indicates that the Smoluchowski theory is applicable to limited coagulation systems and that it overestimates the coagulation rate considerably when applied to common aqueous dispersions. It is also found that the change of particle concentration is conveniently estimated by a kinetic equation in which the coagulation rate between unequal particles is approximated by that between equal spheres.