Rheology of inertial particles by means of experimental observations and numerical simulations

了解河流、湖泊和沿着洋底的沉积物迁移是开放水体和水生生态系统可持续管理的关键。突出的过程是河流形态动力学，浊流，海啸运行的海滩。预测和管理这些过程需要深入了解流变学，以描述流体-沉积物混合物的宏观性质。然而，本构关系来描述这些过程，到目前为止，大多是基于中性浮力颗粒在高粘性剪切流或在大得多的流量惯性效应起主导作用的稠密悬浮液的研究。然而，这两种制度之间的过渡尚未得到系统的研究，因此，人们对这一过渡的了解仍然很少。这可能是有问题的预测建模的情况下，更相关的工程实践和自然流动，涉及泥沙输运。这一过渡制度将是本研究的重点，我们的目标有两个方面：首先，法国和德国的合作伙伴旨在分别进行一项最先进的沉积物输运实验和数值模拟的联合补充活动。该活动将产生高分辨率的数据，层流压力驱动的剪切流穿过理想化的沉积物床的斯托克斯数作为竞争的惯性和粘性效应的比率的范围很广。在第二步中，这些数据将用于改进现有的两相建模方法，这些方法已成为宏观沉积物输运模型的流行方法。

Understanding sediment transport in rivers, lakes and along the ocean floor is key to sustainable management of open water bodies and aquatic ecosystems. Prominent processes are river morphodynamics, turbidity currents, and tsunamis running up a beach. Predicting and managing these processes requires in-depth knowledge of the rheology to describe macroscopic properties of the fluid-sediment mixture. However, the constitutive laws to describe these processes have so far mostly been based on studies of dense suspensions of neutrally buoyant particles in either highly viscous shearing flows or at much larger flow rates where inertial effects play the dominant role. The transition between the two regimes, however, has not been investigated in a systematic manner yet, and, hence, remains only poorly understood. This may be problematic for the predictive modeling of situations that are more relevant for engineering practices and natural flows involving sediment transport. This transitional regime will be the focus of the present study and our objectives are twofold: First, the French and German partners aim to conduct a joint complementary campaign of state-of-the art sediment transport experiments and numerical simulations, respectively. The campaign will yield highly-resolved data of laminar pressure-driven shearing flows across an idealized sediment bed for a wide range of Stokes numbers as the ratio of competing inertial and viscous effects. In a second step, these data will be used to improve existing two-phase modeling approaches that have become popular for macroscopic sediment transport models.