Structural and Phase Transition in Wet Granular Media

Abstract

In granular media, a macro-view deformation reflects the structural change at the particle level. A structural change is widely considered as the phase transition. Due to wide industry applications, such as food storage, mineral transportation, geotechnical engineering, additive manufacturing, and pharmaceutical production, the phase transition of granular media is of great significance. Although researchers have been intensively investigating the phase transition phenomena and the accompanying structure formations in recent decades, challenges still remain in predicting and controlling structures, from ordered structures to random very loose packing, especially under a partially saturated condition where cohesion can be raised.

In this thesis, the structure formation process and the granular phase transition with a focus on partially saturated conditions are investigated. Experiments and numerical simulations show how particle size, cohesion and external excitations can be controlled to achieve tailored phase transition and packing structures in a wide packing fraction range from random very loose packing to crystallisation. Furthermore, the combined effects of cohesion, inertia and gravity during the phase transition can be successfully characterised by several bespoke dimensionless numbers. The findings deepen our understanding of phase transition and structural formation mechanisms of granular materials under various conditions. The effective methods to examine and analyse particle movement and interactions provide insights into predicting and controlling phase transitions and structures.