1. Flow in silos and definitions

As mentioned in the introduction, numerous studies have been carried out on the flow of divided solids for different types/shapes of silos and different powders. While a large number of publications have been devoted to cohesive powders, granular solids (powders with large particle sizes) also pose certain difficulties that deserve to be studied and elucidated. The aim of this article is not to present an exhaustive bibliographical review for all materials. In the literature, numerous works describe the fundamental mechanisms involved, covering a wide spectrum of cases