Investigation of the settling behavior of arbitrarily shaped particles in diluted and concentrated suspensions

悬浮在化学、生物和环境工程的许多技术和非技术过程中都会发生。废水处理和矿石处理是高度多分散、非均相悬浮液处理发挥主要作用的两个领域。在建模和模拟这些过程时，通常假设粒子是球形的。但是粒子很少是完全球形的。根据它们的形状不同，会产生不同的影响，这些影响会极大地影响颗粒系统的沉降行为。纤维悬浮物只是一个例子。在沉淀过程中，纤维可以改变它们的方向。与球的悬浮液不同，这导致沉降速度随浓度的增加或减少。数值模拟已被证明是研究过程工程中许多问题的有效工具。特别是在CFD和离散元耦合模拟领域，近年来出现了处理非球形颗粒的新方法。然而，这些方法仅限于模拟简单的凸几何，如凸多面体或由球形粒子组成的粒子。原则上，后一种方法可用于模拟任意形状的粒子。但是要精确地模拟复杂粒子，需要大量的球体。拟议项目的目的是研究任意形状的颗粒的沉降行为，其几何形状不能用简单的解析表达式来描述，在稀释和浓缩悬浮液中。为了实现这一点，将使用一种数值模型，该模型专门用于模拟任意形状几何形状的运动。此外，对任意形状颗粒的接触进行正确建模的方法将被扩展并包括在开发的模拟包中，以允许模拟浓缩悬浮液。微ct测量产生三维数据的几何形状的任意形状的颗粒在微米范围内的分辨率。利用这些测量数据，模拟将通过沉降实验来验证关于悬浮液中任意形状颗粒的时间演化。基于广泛的数值实验，利用现有的模拟平台进行，将开发新的方法，用它来描述悬浮液中任意形状颗粒的沉降行为。这些方法只取决于选定的一组参数。提出的项目是迈向模拟平台的第一种方法，可以研究真实的任意形状颗粒的沉降行为。

Suspensions occur in many technical and non-technical processes in chemistry, biology and in environmental engineering. Waste water treatment and ore processing are only two fields in which the treatment of highly polydisperse, heterogeneous suspensions plays a major role. When modelling and simulating such processes, particles are usually assumed to be spherical. But particles are seldom perfectly spherical. Depending on their shape, different effects can occur, which can influence the settling behaviour of a system of particles immensely. Suspensions of fibres are just one example. During settling, fibres can change their orientation. Unlike in suspensions of spheres, this results in a concentration dependant increase or decrease of the settling velocity.Numerical simulations have proven to be an effective tool for the investigation of a number of problems in process engineering. Especially in the field of simulations using a coupling of CFD and the discrete-element method, recently new approaches for the treatment of non-spherical particles have been developed. However, these approaches are limited to the simulation of simple convex geometries, such as convex polyhedrons, or particles composed of spherical particles. In principal the latter method can be used to simulate arbitrarily shaped particles. But a high number of spheres is necessary to model complex particles with good accuracy. The aim of the proposed project is the investigation of the settling behaviour of arbitrarily shaped particles, whose geometry cannot be described by simple analytical expressions, in diluted as well as in concentrated suspensions.In order to achieve this, a numerical model will be used, which has specifically been developed for the simulation of the movement of arbitrarily shaped geometries. Furthermore, approaches for the correct modelling of the contact of arbitrarily shaped particles will be extended and included into the developed simulation package, to allow for the simulation of concentrated suspensions. µ-CT measurements yield 3D data of the geometry of arbitrarily shaped particles with a resolution in the range of microns. Using data from such measurements, the simulation will be validated against sedimentation experiments regarding the time evolution of arbitrarily shaped particles in a suspension. Based on extensive numerical experiments, conducted with the now available simulation platform, new approaches will be developed, with which the settling behaviour of arbitrarily shaped particles in suspensions can be described. These approaches shall only depend on a chosen set of parameters. The proposed project is a first approach towards a simulation platform, with which the settling behaviour of real, arbitrarily shaped particles can be investigated.