The Medium Amplitude Oscillatory Shear of Colloidal Dispersions

James W. Swan

Department of Chemical Engineering





The response of colloidal dispersions to Medium Amplitude Oscillatory Shear (MAOS) is investigated via micro-mechanical theory and Brownian dynamics simulation. The first, second and third harmonics of the stress response are determined using an excluded annulus model for the hard-core repulsion and hydrodynamic interactions among the particles. Importantly, the influence of hydrodynamic forces, both in magnitude and in character, on the MAOS of colloidal dispersions is made explicit through comparison of different nonlinear rheological measures, the dispersion microstructure, and experimental results. I will show that hydrodynamic forces have a considerable effect on the microstructure of dispersions undergoing MAOS. As a consequence, the unsteady rheology of suspensions is quite sensitive to dissipative forces between particles.