On the rheology and microstructure of wizarding quidditch ball suspensions

This study focuses on dense frictional non-Brownian suspensions, and it is motivated by one central question: "What is the role of particle shape in dense frictional non-Brownian suspensions?". Answering this question has so far remained elusive due to the difficulties that arise, such as characterizing the shape, detecting the contact points among particles and calculating forces among particles of arbitrary shape. In this talk, we present our experimental results on the shear-reversal experiments and rheological characterization of dense frictional suspension. More specifically, our system of study includes suspensions of crushed and spherical particles of the same materials in the same solvent. We shear the suspensions for a wide range of stresses. We benefit from the measurements of the advanced force microscopy and characterization of the rheology to carefully examine the role of adhesion forces at small shear stresses and the role of particle shape disentangled from adhesion forces at large imposed shear stresses. Our experiments shed light on the pure role of particle shape independent of the surface forces on the hydrodynamic interactions, sliding and rolling friction and consequently the microstructure and rheological behavior of the non-Brownian suspensions.