Migration and dynamics of particles in complex geometries and flows

复杂几何形状和流动中粒子的迁移和动力学

• 批准号: 417989464
• 负责人: Professor Dr. Jens Harting
• 金额: --
• 依托单位: Abteilung RU-C: Dynamics of Complex Fluids and Interfaces
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/417989464?language=en
• 关键词: Migration; dynamics; particles; complex; geometries

Practical flows generally contain an unsteady component, e.g. due to an external driving or pulsation. This adds an additional external timescale to the system which eventually can strongly influence the onset of instabilities. The understanding of the impact of this additional timescale is at the core of the motivation for this research unit. The effect of the external timescale is even more important for complex fluids, i.e. particle suspensions, where an additional relaxation timescale is involved. This project aims at an understanding of the interplay between fluid properties, inertia and confinement on the particle migration and the onset of instabilities. At very low Reynolds numbers (Stokes limit), a lot is known about particle migration and structuring, while inertial forces are not relevant. On the other side of the scale, at very high Reynolds numbers, turbulence is fully developed and we expect inertia to be dominant. We will focus on the intermediate regime at moderate Reynolds numbers between 1 and 1500. Here, the combination of inertial forces and the properties of the complex fluid or the confinement have a defined impact on the transport properties. We will use a simulation technique combining the lattice Boltzmann method for the fluid dynamics at Navier-Stokes level and a discrete element algorithm for the description of suspended particles. For soft particles, a finite element/immersed boundary method will be used. The method is highly flexible with respect to particle and fluid properties as well as the implementation of confining geometries. It is particularly well suited for the regime of interest: the inertial term in the Navier-Stokes equation is recovered, the internal structure of the complex fluid can be resolved, complex geometries and driving forces are easily implemented and it scales to experimentally relevant time and length scales due to its inherent parallelism. With this tool at hand, at first we will focus on suspensions with hard and soft particles in pulsating flows and investigate the impact of the particle volume concentration (from Newtonian to non-Newtonian) and inertia on the particle migration and suspension transport in simple geometries. We will study if and how instabilities of the flow can occur for these systems. Furthermore, we will study the impact of confinement on inertia-driven suspensions. We aim to understand how to make use of the channel geometry to generate a structuring or even sorting of the particles. Finally, we will study the impact of shear thinning or viscoelastic fluids on the transport properties of a suspension in pipe flows and in more complex geometries.

实际流动通常包含不稳定分量，例如由于外部驱动或脉动。这给系统增加了一个额外的外部时间尺度，最终会强烈影响不稳定性的发生。对这一额外时间尺度的影响的理解是本研究单元动机的核心。外部时间尺度的影响对于复杂流体（即颗粒悬浮液）甚至更重要，其中涉及额外的弛豫时间尺度。该项目旨在了解流体性质，惯性和粒子迁移和不稳定性发生的限制之间的相互作用。 在非常低的雷诺数（斯托克斯极限），很多是已知的粒子迁移和结构，而惯性力是不相关的。在尺度的另一边，在非常高的雷诺数下，湍流充分发展，我们预计惯性占主导地位。 我们将集中在中等雷诺数1和1500之间的中间制度。这里，惯性力和复杂流体的性质或限制的组合对传输性质具有确定的影响。我们将使用模拟技术相结合的格子玻尔兹曼方法的流体动力学在Navier-Stokes水平和离散元算法的描述悬浮颗粒。对于软颗粒，将使用有限元/浸入边界法。该方法是高度灵活的颗粒和流体的性质，以及实施限制的几何形状。 它特别适合于感兴趣的制度：Navier-Stokes方程中的惯性项被恢复，复杂流体的内部结构可以被解析，复杂的几何形状和驱动力很容易实现，并且由于其固有的平行性，它可以扩展到实验相关的时间和长度尺度。有了这个工具在手，首先，我们将集中在脉动流中的硬颗粒和软颗粒的悬浮液，并研究颗粒体积浓度（从牛顿到非牛顿）和惯性对简单几何形状中的颗粒迁移和悬浮液传输的影响。我们将研究这些系统是否以及如何发生流动的不稳定性。此外，我们将研究约束对惯性驱动悬架的影响。我们的目标是了解如何利用通道的几何形状来产生一个结构化的颗粒，甚至排序。最后，我们将研究剪切稀化或粘弹性流体对管道流动和更复杂几何形状中悬浮液输运性质的影响。