Suspension droplet wall impingement and particle deposition

悬浮液液滴壁撞击和颗粒沉积

• 批准号: 464601110
• 负责人: Professor Dr.-Ing. Martin Sommerfeld
• 金额: --
• 依托单位: Institut für Verfahrenstechnik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/464601110?language=en
• 关键词: Suspension; droplet; wall; impingement; particle

The project aims to analyse suspension droplet wall impacts experimentally and by numerical simulations. This is a complex and rarely studied topic, but is of fundamental importance for numerous technical processes. These are: spray painting, spray drying, composite surface coating, coating of pharmaceuticals, and single droplet processes, such as ink-jet printing, printing of biomaterials and electronic circuits. Experiments will be conducted for obtaining the regimes of droplet impact, such as deposition, rebound and splashing, summarised by relevant non-dimensional parameters. Moreover, droplet spreading, formation of deposits on the walls and the properties of rebound fragments will be studied.Experiments are planned for millimetres droplet sizes, different impact angles, velocities, and wall materials. Various liquids and different volume fractions of solid particles will be considered to obtain a comprehensive understanding of the complex droplet wall impact. Also, different sizes and material densities of the enclosed particles will be considered to analyse the effect of particle inertia on the impact. For visualising the droplet impingement direct shadowgraph imaging techniques will be applied in combination with LED illumination and high-speed camera recording. These techniques will allow not only to study possible drop impact outcomes but also to monitor particle motion inside spreading drops along with final particle distribution.Complementary numerical simulations will be conducted for predicting droplet behaviour during impact as well as the particle motion inside the droplet and eventually the structure of wall deposition. For dealing with such a complex three-phase flow problem a number of extensions of the available numerical code based on the Euler/Lagrange principle have to be done. The basis of the numerical simulations will be the OpenFOAM library, which was already extended at the institute with a number of features needed for the present task. The behaviour of the droplets itself during wall impact will be solved by a VoF method with geometrical reconstruction of the liquid interface using the isoAdvector. The solid particles dispersed inside the droplet will be treated by a point-particle Lagrangian method, considering all relevant forces. Two-way coupling and inter-particle collisions will be also considered. Moreover, the interaction of the particles with the droplet interface and the solid wall requires additional forces to be considered. Finally, particle wall adhesion will be considered in order to predict the formation of the particle deposits on the wall. Model parameters needed, will be provided by the detailed experimental studies, e.g. for the particle-wall collisions in a liquid. The extended numerical code will be verified with the thorough experiments. Overall, this project will lead to a detailed knowledge and provide design rules for processes applying suspension droplet wall collisions.

该项目旨在通过实验和数值模拟来分析悬浮液滴对壁面的影响。这是一个复杂且很少被研究的话题，但对于许多技术流程来说却是至关重要的。它们是：喷漆、喷雾干燥、复合表面涂层、药物涂层和单滴工艺，如喷墨打印、生物材料打印和电子电路。将进行实验，以获得液滴撞击的区域，如沉积、反弹和飞溅，由相关的无量纲参数总结。此外，还将研究液滴的扩散、壁上沉积的形成和反弹碎片的特性。计划针对毫米液滴尺寸、不同的撞击角、速度和壁面材料进行实验。将考虑不同的液体和不同体积分数的固体颗粒，以获得对复杂液滴壁面影响的全面了解。此外，还将考虑不同尺寸和材料密度的封闭颗粒，以分析颗粒惯性对撞击的影响。为了可视化液滴撞击，直接阴影成像技术将与LED照明和高速摄像机记录相结合。这些技术不仅可以研究液滴撞击的可能结果，还可以监测扩散液滴内的颗粒运动以及最终的颗粒分布。将进行完整的数值模拟，以预测液滴在撞击过程中的行为以及液滴内部的颗粒运动，并最终了解壁面沉积的结构。为了处理这样一个复杂的三相流问题，必须对现有的基于欧拉/拉格朗日原理的数值程序进行大量的扩展。数值模拟的基础将是OpenFOAM库，该库已经在研究所进行了扩展，具有本任务所需的一些功能。在壁面碰撞过程中，液滴本身的行为将通过VOF方法求解，其中液体界面使用等伸缩矢量进行几何重建。分散在液滴内部的固体颗粒将用点-质点拉格朗日方法处理，并考虑所有相关的力。双向耦合和粒子间碰撞也将被考虑。此外，颗粒与液滴界面和固体壁面的相互作用需要考虑附加力。最后，为了预测颗粒在壁面上沉积的形成，将考虑颗粒壁面的粘附性。所需的模型参数将由详细的实验研究提供，例如液体中的颗粒-壁面碰撞。扩展后的数值代码将通过深入的实验进行验证。总体而言，该项目将带来详细的知识，并为应用悬浮液滴壁面碰撞的过程提供设计规则。