A novel and unified solution to multi-phase mass flows

泥石流是由土、沙、岩、水等在重力作用下形成的混合流。固体颗粒和粘性流体控制流变特性，它们的耦合显著影响动力学。泥石流可大大增加其体积和破坏潜力，并通过夹带河床沉积物而变得异常移动的。混合物组成可以演变以显著改变颗粒和流体的空间分布，从而改变摩擦阻力和粘性阻力。因此，在泥石流动力学过程中，物质成分对侵蚀沉积和固液相分离的影响是至关重要的。正确理解这些复杂的物理过程对于准确描述冲击力、淹没区域、景观演变和制定可靠的减灾计划非常重要。预测泥石流的侵蚀、相分离和沉积过程是一个长期存在的挑战。然而，由于缺乏数据和合适的模型，目前还没有一种包括所观察到的侵蚀、被侵蚀物质的夹带和扩散、颗粒分选、相分离、堤坝形成和沉积模式的径流预测方法。（波恩大学），他们的验证与独特的良好控制的开拓性实验（乌得勒支大学），我们的目标是开发一种新的，统一的，有效的和完全耦合的解决方案，这些真正的多相，三维质量流问题。由于泥石流是更好地描述了一个三相混合物，包括粘性流体，细颗粒和粗颗粒相比，经常使用的单相模型，建议的模型包括三个阶段，包括屈服强度。由于当陆地撞击水体时，波的色散起着关键作用，因此我们的新模型包括了非流体静力学效应。这种统一的三相方法的优点是，可以获得侵蚀、相分离、泥石流向浊流转化的相互关联的过程及其对水流结构、组成和沉积的影响。该模型将进行新的实验与多组分侵蚀泥石流结合所有复杂的管理过程进行验证。这些过程包括干层和饱和层的侵蚀、夹带、颗粒分选、相分离、堤/瓣形成、从陆上到海底环境的流动转变以及具有可变储层流体水平的碎屑沉积物的演变。因此，该项目产生了一个先进的开源质量流模拟模型，旨在准确预测泥石流动力学、相分离、侵蚀、沉积和径流。因此，该模型将大大有助于减轻泥石流灾害，减少世界各地的损害和死亡人数。

Debris flows are gravity driven mixture flows of soil, sand, rock and water. The solid particles and viscous fluid governs the rheological properties, and their coupling significantly influences the dynamics. Debris flows can dramatically increase their volume and destructive potential, and become exceptionally mobile by entraining bed sediment. The mixture composition can evolve to strikingly change the spatial distribution of particles and fluid, and thus frictional and viscous resistance. So, erosion-deposition and phase-separation between solid and fluid, which strongly depend on material composition, play a critical role in debris flow dynamics. Proper understanding of these complex physical processes is very important in accurate description of impact forces, inundation areas, landscape evolution and developing reliable mitigation plans. Predicting the underlying processes of erosion, phase-separation and deposition in debris flow are long-standing challenges. However, due to lack of data and suitable models, there exists no runout prediction method that includes observed processes of erosion, entrainment and diffusion of eroded material, grain sorting, phase-separation, levee formation and deposition patterns.Based on innovative mechanical models for erosion-deposition and phase-separation that explicitly consider changes in local flow compositions (Univ. Bonn), and their validations with unique well controlled pioneering experiments (Univ. Utrecht), we aim to develop a novel, unified, efficient and fully coupled solution to these true multi-phase, three-dimensional mass flow problems. As debris flows are better described by a three-phase mixture that include viscous fluid, and fine and coarse grains as compared to often used single-phase models, proposed model consists of three-phases including yield strength. As wave-dispersion plays a critical role when a landmass impacts a water body, our novel model includes non-hydrostatic effects. Great advantage is that with such a proposed unified three-phase approach, realistic inter-connected processes of erosion, phase-separation, flow transformation from debris flow to turbidity current and their influences on the flow structure, composition and deposition can be achieved. The model will be validated by conducting new experiments with multi-component erosive debris flows combining all complex governing processes. These processes include erosion of dry and saturated beds, entrainment, particle sorting, phase-separation, levee/lobe formation, flow transformation from the subaerial to submarine environment and evolution of debris deposits with variable reservoir fluid level. Thus, this project results in an advanced open source mass flow simulation model aiming to accurately predict debris flow dynamics, phase-separation, erosion, deposition and runout. As such, the model will substantially help debris-flow hazard mitigation and reduce damage and fatalities worldwide.