Substrate impact 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，过滤中的沉积物和颗粒输送、天然水道和管道系统、呼吸系统中的颗粒输送以及表面的清洁都可以提到。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。尽管有许多关于粒子运动的开始，运动本身或更确切地说，物质传输的研究，这些技术上重要的过程仍然没有很好地描述。这是由于颗粒去除只研究了无序沉积层，并试图在现有模型中使用没有明确定义的参数来描述。由于忽略了精确的颗粒排列，基材几何形状的影响，暴露于流动和邻近颗粒的阴影仍然不清楚。因此，衬底几何形状和邻近粒子对粒子运动的开始和沿着衬底本身运动的影响仍然不清楚。颗粒床在两个方面阻碍了颗粒的运动：一方面，不均匀的基材形成了一个障碍，下游的接触角必须克服，另一方面，它遮蔽了颗粒的流动。以类似的方式，邻近的粒子起到额外的阻碍作用。从这个观察开始，我们计划改变相关的参数。该项目的目的是在一个模型中定量地描述粒子运动的开始和沿着基底本身的层流剪切流的运动，而不依赖于没有明确定义的参数。

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 filtration, 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. Despite numerous studies concerning the onset of particle motion, the motion itself or rather the material transport, these technologically important processes are still not well described. This is due to the fact that particle removal has been studied exclusively for disordered sediment layers and has been tried to describe using not well-defined parameters in the existing models. Since the precise particle arrangement is ignored, the effects of substrate geometry, exposure to the flow and shading by neighboring particles remains unclear. Hence, the impact of substrate geometry and of neighboring particles on the onset of particle motion and the motion along the substrate itself remains unclear.Granular beds hinder particle motion in two ways: On the one hand, the uneven substrate poses an obstacle, which downstream contact angle has to be overcome, on the other hand, its shades the particle against the flow. In an analogue manner, neighboring particles serve as an additional hindrance. Starting from this observation, we plan to vary the relevant parameters. The aim of the project is to describe the onset of particle motion and the motion along the substrate itself in laminar shear flows quantitatively in a model without recourse to not well-defined parameters.