High-performance numerical methods for modelling of granular flows and sediment dynamics

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Granular materials are made up of macroscopic small particles, of which sediment material is an important example. These materials are ubiquitous in nature and are the second-most manipulated material in industry (water being the first). Flow of granular materials plays a critical role in engineering, geophysical and environmental processes. It may seem confounding that in the today's world of scientific advancements, the flow of this most familiar form of matter remains largely unpredictable. This knowledge gap stems from the complex mechanical behaviour of these materials which may resemble those of solid, liquid (a non-Newtonian fluid) or even gas in different circumstances. The situation is still more complex when the granular material interacts with an ambient fluid like water. Predicting the behaviour of these so-called multiphase granular flows is critical to furthering today's limited understanding of fluvial and coastal sediment dynamics, submarine landslides, or slurry flow in tailing ponds of mining operations. With advances in computing power and numerical algorithms, it has become possible to numerically simulate granular flow systems, especially where physical models are restricted. Nevertheless, dealing with the complexities of multiphase granular flows is still beyond the capabilities of the many existing numerical methods. This is due to the complicated behaviour of granular material and the large deformations and fragmentations that exist at the interface of the ambient fluid and the granular material. Furthermore, to deal with the in-depth analysis of multi-scale problems, the cluster “peta-scale” computing is required. The development of a revolutionary generation of numerical techniques, the mesh-free Lagrangian (particle) methods, has provided us the first ever opportunity to overcome the granular flows complexities. These methods are known to be capable of handling the multiphase continuum with complex boundaries and interfaces. The proposed program, therefore, aims to (1) elaborate the theoretical foundation, describing the mechanics of multiphase granular flows, and develop novel algorithms, primarily based on the mesh-free Lagrangian methods, for numerical implementations; (2) improve the robustness and accuracy of these numerical techniques; and (3) develop massively parallel, accurate, and multi-scale algorithms, capable of PetaFLOP computation of these flow systems. The focus will be on development of models that permit accurate representation of the grain-scale motions and then harnessing the full power of modern computers to achieve scalable performance on large-scale problems. This program also aims to (4) provide new understanding of mechanisms involved in real-life multiphase granular flows, particularly for the case of sediment dynamics analysis in fluvial environments, mining tailing slurries and landslides.