There is a complex interaction between the dynamics of a flowing material and its grain size. The grain size distribution can change in space for many reasons, all of which are poorly understood. Here, I will present recent experimental advances which allow us to probe inside flowing material and observe these phenomena. The insights we have gained from these observations are allowing us to describe quantitatively the evolution of the grain size distribution to a plethora of competing mechanisms, such as segregation, mixing and breakage. I will show how simple numerical models can capture this behaviour and describe how these can be easily extended to complete mechanical models which couple realistic flow rheology with grainsize dynamics.
Dr Marks is a Lecturer in the School of Civil Engineering at The University of Sydney. His research is based in the mechanics of granular media, in particular the processes of segregation, mixing and grain crushing. He is involved in developing new X-ray based techniques for investigating the interior of these materials in a dynamic environment, giving us the ability to measure the evolving velocity and grain size distribution fields over time. These new measurements are the key to enable us to create and validate new mathematical and computational tools for understanding this complex behaviour.