Analytical nonlocal model for shear localization in wall-bounded dense granular flow

This work employs a Landau-Ginzburg-type nonlocal rheology model to account for shear localization in a wall-bounded dense granular flow. The configuration is a 3D shear cell in which the bottom bumpy wall moves at a constant speed, while a load pressure is applied at the top bumpy wall, with flat but frictional lateral walls. At a fixed pressure, shear zones transit from the top to the bottom when increasing lateral wall friction coefficient. With a quasi-2D model simplification, asymptotic solutions for fluidization order parameters near the top and bottom boundaries are sought separately. Both solutions are the Airy function in terms of a depth coordinate scaled by a characteristic length which measures the width of the corresponding shear zone. The theoretical predictions for the shear zone widths against lateral wall friction coefficient and load pressure agree well with data extracted from particle-based simulation for the flow.

Modelling of scour formation using SedFoam, continuum approach

SedFOAM is a two-phase flow solver built upon consecutive laws, based on the CFD toolbox OpenFOAM. The sediment body is considered as a continuum phase. The intergranular and fluid stresses are modeled with the dense granular flow rheology and the k–ϵ turbulent model, respectively. The model setup will be based on an experimental study on the scour due to a water jet subjected to lateral confinement. A comparison study will be made based on precise experimental data by Martino et al. (2019) that will show the advantages and defaults of SedFoam. The objective of this work is to reproduce the digging and filling cycle of the scour formation due to the water jet in a confined canal. The first numerical results show that it needs to use 3D numerical simulations because of the fluctuation of the jet direction induced by the presence of a driven flow cavity.

Magnetic-Based Particle Tracking in a Dense Granular Shear Flow

Granular material is ubiquitous in nature and plays a significant role in industry. Researchers have paid a lot of attention to density and velocity distributions of dense granular flows. However, the motion of individual particle is hard to capture because visualizing individual particles in a dense granular flow, especially in 3D, is very difficult and could be expansive. Here we use the magnetic particle tracking (MPT) technique to capture the motion of a single particle in a sheared dense granular flow. The accuracy of MPT is quantified using experimental results. The sheared granular flow is generated in a Couette cell by rotating a plate at the bottom of a cylinder container. It is able to generate different shear stresses by controlling the speed of the plate. By tracking the magnetic particle in the cylinder, we can capture the velocity of an individual particle at different locations in the granular flow.