(3bp) Large Amplitude Oscillatory Flow, a Microstructural Perspective

A microstructural understanding of the origin of the large-amplitude rheological response of materials is an on-going challenge.  I have conducted a detailed study of the response to large amplitude oscillatory flows (LAOF) from a micromechanical perspective -- the microrheology of colloidal dispersions. The solution to this problem combines the micro-viscoelasticity with the material microstructure and provides considerable insight into the physical processes involved in large amplitude flows.  In particular, the relative importance of hydrodynamic and thermal forces determines the amount of energy stored and lost during the process.  Interestingly, while hydrodynamic interactions are largely responsible for the behavior of strongly driven materials, I show that hydrodynamics cannot contribute to net energy storage.  A comparison of the response for driven suspensions with and without hydrodynamic interactions reveals that a detailed understanding of the material microstructure is necessary for meaningful interpretation of large amplitude oscillatory flows.  This simple model provides such details and recovers the rich behavior observed experimentally in a broad class of materials -- ranging from colloidal dispersions to polymer melts and even slug mucus.