Controlling rheology via boundary conditions in dense granular flows

Abstract

Boundary shape, particularly roughness, strongly controls the amount of wall slip in dense granular flows. In this paper, we aim to quantify and understand which aspects of a dense granular...

Visualizing flow dynamics and restart of Carbopol gel solutions in tube and parallel-plates geometries with wall slip

“…Wall shear stress not only induces the movement of the material but also directly influences the velocity gradient and slip velocity. This is observed in the work of Kalyon, 103 where it is shown that the applied shear stress determines the velocity profile in the fluid and the extension of wall slip.…”

“…The intrinsic properties of the material, such as its viscosity and yield stress, along with the non-uniform distribution of the applied stress and the characteristics of the internal gel network, contribute to the persistence of slip. 102,103 Nevertheless, it is possible to determine that there is a value within a range of low shear stresses where elastic (solid-like) and viscous behaviors coexist, 104 from which wall slip occurs and the material can start yielding from a rest state. In other words, there is a transition state markedly affected by wall slip that facilitates the onset of flow with low shear stresses and significant deformations.…”

Dynamic compaction of cohesive granular materials: scaling behavior and bonding structures

“…Such wall effects are common in cohesionless packings and their presence together with a small gradient of forces from the walls towards the center of the box indicate that mesoscopic force inhomogeneities occur in our system on top of the well-known particle scale force inhomogeneity. 60,69–73 At higher cohesion (Fig. 13(b)), we observe both compressive and tensile force chains.…”

The (In)sensitivity of Granular Creep to Materials and Boundaries

“…This interpretation is consistent with observations of aging in jammed and confined amorphous solids (C. Cao et al., 2017; J. Liu et al., 2020). Rough boundaries in slowly sheared granular materials not only frustrate ordering of grains near the boundary, but are also responsible for large‐magnitude force‐chain fluctuations (Fazelpour & Daniels, 2021, 2023; Fazelpour et al., 2022); this could be the “soft‐spot injection” mechanism. To sustain creep indefinitely, as appears to occur in nature on hillslopes, soil creep must be rejuvenated by the continuous injection of energy or disorder.…”