Impact of inertia on flow-induced particle motion in laminar shear flow

固体颗粒在固定基质或颗粒床上的流动引起的脱离和运动在许多自然和工业系统中具有基本的相关性。作为例子，可以提到输送、过滤、分馏、天然水道和管道系统中的沉积物和颗粒输送、呼吸系统中的颗粒输送以及表面的清洁。在微流体中，球形颗粒逐渐被用作信息载体或阀门或泵等执行器。因此，一个重要的前提是粒子的可控定位。虽然单个粒子在光滑壁上的运动已经很好地理解了，但这并不适用于结构表面和颗粒床。这主要是因为大量的研究只在无序沉积层中研究了物质的运移，特别是颗粒的运动及其开始，并试图在模型中使用没有明确定义的参数来描述。最近，我们可以提供一个定量的确定性描述运动和它的开始在蠕动流动的限制，而不必回到数据拟合。它是基于在结构基板上进行的良好定义的实验，以及对作用的流致力和扭矩的数值计算。惯性对初始运动的影响仍然是一个悬而未决的问题。预计它将产生深远的影响，从对运动开始的临界屏蔽数和分岔类型的影响，到对剪切载荷持续时间的依赖，以及与基底地形的共振。在提议的项目中，我们打算回答这些问题。

Flow induced detachment and motion of solid particles on a fixed substrate or granular bed is of fundamental relevance in numerous natural and industrial systems. As examples sediment and granular transport in conveying, filtration, fractionation, natural watercourses and piping systems, particle transport in the respiratory system, and the cleaning of surfaces may be mentioned. In microfluidics, spherical particles are progressively used as information carrier or for actuators like valves or pumps. Therefore, an important precondition is the controlled positioning of particles. While the motion of single particles on smooth walls is quite well understood, this does not hold for structured surfaces and granular beds. This is mainly because the material transport and especially the particle motion and its onset has been studied in the numerous studies exclusively in disordered sediment layers and has been tried to describe using not well-defined parameters in the models. Recently, we could provide a quantitative deterministic description of the motion and its onset in the creeping-flow limit without harking back to data fitting. It is based on well-defined experiments with structured substrates together with numerical calculations of the acting flow-induced forces and torques. The impact of inertia on the incipient motion remains an open question. It is expected to have far-reaching implications ranging from the impact on the critical Shields number for the onset of motion and the type of bifurcation to the dependence on the duration of the shear load and to resonance with the substrate topography. In the proposed project, we intend to answer these questions.