2025 AIChE Annual Meeting

(600e) Rheology and Microstructure of Dense Suspension Under Shear Reversal

Authors

Abhinendra Singh - Presenter, Case Western Reserve University
Ryan Pappalardo, Case Western Reserve University
Alessandro d'Amico, Case Western Reserve University
Shweta Sharma, Case Western Reserve University
Sidong Tu, Case Western Reserve University
Michel Orsi, City College of New York
Dense suspensions are dispersions of small particles in a Newtonian solvent that are ubiquitous in nature and industry. They often show a pronounced increase in viscosity under large deformation and shear thickening. Recent research has linked stress-activated frictional contacts to strong shear thickening, which often manifests as an abrupt increase in viscosity at a critical shear rate called discontinuous shear thickening (DST). In this work, we use a simulation tool LF-DEM that combines lubrication flow (LF) with discrete element method (DEM) to simulate inertialess buoyant particles dispersed in a Newtonian solvent. To elucidate the role of different types of attraction, we employ shear reversal under constant shear stress. At the volume fractions close to the frictional jamming volume fraction, the frictional contacts do not decay to zero under reversal. These "persistent contacts" show a two-step relaxation at the reversal. We present a combined approach linking macroscale rheology, microscale coordination number, and mesoscale contact network analysis.