From crystallisation to polydispersity: a multi-scale analysis of dry dense granular flows

Details

Supervisors

Legat, Vincent ; Lambrechts, Jonathan

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil mécanicien, à finalité spécialisée

Abstract

enDense granular flows are encountered in many natural and industrial processes, yet their rheology remains incompletely understood. Using the open-source MigFlow software, this thesis investigates the rheology of dry dense granular materials through two-dimensional plane Couette shear simulations under imposed confinement pressure. Monodisperse assemblies were first simulated across a range of inertial numbers to characterise the μ(I) rheology. The expected trends were recovered : the effective friction coefficient μ increases and the packing fraction ϕ decreases with the inertial number I, but below a critical value Ic ∈ [0.14, 0.28], the system undergoes crystallisation-induced jamming and locks into a stable hexagonal lattice, making the rest of the dense regime inaccessible. Polydisperse assemblies (uniform radius distribution, λ = dmax/dmin up to 9) were introduced to avoid crystallisation. Studied down to I ≈ 10−3, increasing polydispersity raises the effective friction coefficient, and lowers the equilibrium packing fraction. The constitutive parameters of the μ(I) law were identified for each polydispersity level, and their monotonic dependence on λ was quantified. In short, this thesis showed that the μ(I)-rheology model was recovered for polydisperse assemblies using the Migflow framework.