Capture efficiency and coagulation rate of polystyrene latex particles in a laminar shear flow: Effects of ionic strength and shear rate

Coagulation rates of polystyrene latex particles in a simple shear flow were measured to confirm the validity of numerical results of colloidal stability in flow fields. Experiments were performed in a laminar Couette flow generated in the gap between two concentric cylinders, using dispersions of monodisperse spheres of polystyrene latex. Absolute rates of coagulation in the initial stage were measured by a Coulter counter as functions of KCl concentration and shear rate. The experimental data were found to agree with the result of numerical analysis. That is, (i) the point of critical coagulation concentration (CCC) shifts to higher value with an increase of shear rate and (ii) the slope of capture efficiency against ionic strength in the slow coagulation regime decreases with an increase of shear rate.