Tangential Forces Govern the Viscous-Inertial Transition in Dense Frictional Suspensions
Phys. Rev. Lett. 136, 248201 – Published 16 June, 2026
DOI: https://doi.org/10.1103/66pp-4rdj
Abstract
We present particle-resolved simulations of dense frictional suspensions undergoing the viscous-inertial transition using pressure-imposed rheology. By varying the fluid viscosity, shear rate, and granular pressure, we demonstrate that the transition occurs at a Stokes number of (close to the value of 10 found in the experiments of Tapia et al. [Viscous to inertial transition in dense granular suspension, Phys. Rev. Lett. 129, 078001 (2022).]) and also that the shear stress exhibits a slower transition than the particle pressure. Using our highly resolved numerical simulations, we further demonstrate that this transitional behavior is related to the combined effect of tangential contact and lubrication forces, as the frictional particles concurrently shift from rolling to sliding contacts. This shift is controlled not only by the Stokes number, but also by the distance from jamming. Additionally, we examine the role of increasing interparticle friction on the viscous-inertial transition.
