Gravity-induced settling of many non-spherical particles at intermediate Galileo numbers: a DNS study

大气中冰粒的运动、海洋中浮游生物的运动以及化学工程装置中悬浮颗粒的运动都是沉降过程的一些例子，其中颗粒沉降速度强烈地取决于它们的空间分布。通过现代实验室实验和数值分析，我们对悬架动力学的基本认识已经取得了相当大的进展。然而，大多数研究将他们的注意力限制在球形固体上，尽管大多数现实世界的应用，如上面提到的那些，都涉及非球形颗粒。在本项目中，我们提出了许多球形颗粒（包括扁长和扁长）通过界面分辨直接数值模拟（DNS）在低固体体积分数和颗粒雷诺数为O（100）的集合的沉降行为进行研究。在这种情况下，Euler-Lagrange（点粒子）模型和Euler-Euler（双流体）模型的建模不确定性特别高，许多非球形粒子的高保真数据实际上是不存在的。在本项目中，我们计划使用的大型数据集，将产生，以回答以下问题：粒子形状如何影响的趋势，形成唤醒诱导集群？粒子运动的统计结果是什么？沉降颗粒系综对流体流动有何影响？可以预期，全面的数据分析将使我们能够提出建议，涉及非球形颗粒的沉降悬浮液的降阶建模。

The motion of ice particles in the atmosphere, of plankton in the oceans, and of suspended particles in chemical engineering apparatuses are some examples of sedimentation processes where the particle settling speed strongly depends upon their spatial distribution. Considerable progress in our fundamental understanding of suspension dynamics has already been gained through modern laboratory experiments and numerical analysis. However, most studies restrict their attention to spherically-shaped solids, although the majority of real-world applications such as the ones mentioned above involve non-spherical particles. In the present project we propose to study the settling behavior of ensembles of many spheroidal particles (both oblate and prolate) via interface-resolved direct numerical simulation (DNS) at low solid volume fraction and for particle Reynolds numbers of O(100. In this regime the modeling uncertainty of Euler-Lagrange (point-particle) models and of Euler-Euler (two-fluid) models is particularly high, and high-fidelity data for many non-spherical particles is practically non-existent. In the present project we plan to use the large data-set which will be generated in order to answer the following questions: How does particle shape influence the tendency to form wake-induced clusters? What are the consequences for the statistics of the particle motion? What is the impact upon the fluid flow induced by the settling particle ensemble? It can be expected that the thorough data analysis will allow us to make recommendations for reduced-order modelling of settling suspensions involving non-spherical particles.