MEchanics GAthering –MEGA- Seminar: Shear jamming in dense suspensions and how to avoid it

Abstract: Dense suspensions exhibit a rich rheology in which viscosity diverges as the packing fraction approaches a critical jamming value  φ_c. Within the pressure-imposed μ(J) framework, particle friction strongly lowers φ_c and gives rise to shear jamming and discontinuous shear thickening, where force chains aligned with the flow lock the suspension into a fragile solid-like state. In this talk, I show how this very fragility can be exploited to avoid jamming: by rotating or perturbing the shear direction — a protocol analogous to tacking against the wind — force chains are disrupted, the effective jamming threshold is pushed to higher packing fractions, and dissipation is reduced in frictional systems. I will also discuss how particle shape introduces a new phenomenon: directional shear jamming, where elongated particles jam along one shear direction but flow freely along another. Together, these results point to practical routes to tune and mitigate jamming through flow protocols and particle design.
 

Bio: Martin Trulsson is a Senior Lecturer in Computational Chemistry at Lund University, Sweden, and currently a visiting professor at Politecnico di Torino. He obtained his PhD from Lund University in 2011, working on molecular simulations of colloidal systems, and subsequently held postdoctoral positions at ESPCI Paris and Université Paris-Sud (Orsay), where his research expanded to the rheology of dense suspensions and electrostatic interactions in soft matter. His current work combines discrete-element and hydrodynamic simulations to understand jamming, shear thickening, and flow protocols in dense particulate systems.