Effect of the polydispersity on immersed column collapse: role of the grain size distribution on the deposit runout
Résumé
Granular column collapse simulations are a benchmark in the study of transitional granular flows [1].
The column collapse is a simplified version of occurring flows in highly varying scales, ranging in
natural debris flows or industrial handling purposes. A characteristic among them is their occasional
submergence in a viscous fluid, resulting in strong grain-fluid interactions between particles of
different sizes [2, 3, 4]. This work studies the effect of polydispersity in the runout of the collapse of
immersed granular columns. For this purpose, we simulate a two-dimensional immersed granular
column employing a coupled discrete and finite element fluid model (DEM-FEM) [5]. In this
configuration, we study granular systems with different grain size distributions (GSD), varying the
ratio between the biggest and smallest particle from 1.2 to 10. We simulate dense granular columns,
varying the initial column height H0 and initial column width L0 through three different aspect ratios
A = H0/L0 = (0.5, 1.0, 3.5). We show that the collapse mechanism and collapse duration strongly
depend on polydispersity. Increasing polydispersity reduces the kinematic energy of the collapse and
reduces the final runout. For short columns A = (0.5, 1.0), the repose angle increases with the
polydispersity until it reaches a plateau near 17°. Our results highlight the effect on the final shape,
flow mechanism, and fluid-grain interaction of increasing polydispersity in transitional immersed
flows.