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Agglomeration and cluster formation of microscacle particles and droplets in highly loaded turbulent gas flows

高负荷湍流气流中微尺度颗粒和液滴的团聚和团簇形成

基本信息

批准号：
215541820
负责人：
Professor Dr.-Ing. Michael Breuer
金额：
--
依托单位：
Professur für Strömungsmechanik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/215541820?language=en
关键词：
Agglomeration cluster formation microscacle particles

项目摘要

The objective of the project is to model, simulate and analyze the dynamic process of particle agglomeration in turbulent, highly loadeddisperse multiphase flows. In the first project period significant progress was made based on a four-way coupled Euler-Lagrange approach relying on the large-eddy simulation technique for the description of complex turbulent flows and a simultaneous particle tracking scheme for the disperse phase. On the basis of a deterministic treatment of the particle-particle collisions two new agglomeration models and a wall adhesion model were developed. These were first validated based on various test cases and for a wide parameter range and then successfully applied for the analysis of the agglomeration processes within turbulent flows of highly loaded fluids. Thereby new insights into the physical relationships concerning the agglomeration of particles and their most important influencing factors as well as the feedback of the agglomerates on the turbulent flow field was gained.The objective of the second project period is to incorporate the effect of breakage of agglomerates which for simplification purposeswas not taken into account yet, but plays a significant role for the description of the entire process. In technical applications thegrowth of agglomerates is the result of the interplay between agglomeration and breakage of the agglomerates leading to thecharacteristic particle size distribution. That in turn decisively determines significant processes such as the separation for example infilters or cyclones, the dosing of pharmaceuticals or the reaction rates in chemical reactors. Therefore, the description of bothphenomena is indispensable for a realistic simulation of highly loaded turbulent two-phase flows.From the list of the three most important mechanisms of breakage particular attention will be paid to the break-up of agglomerates dueto fluid-induced forces. Deviating from the state-of-the-art in the literature (break-up of massless and solely small agglomerates, DNSand mostly homogeneous isotropic turbulence) the fluid-induced break-up of agglomerates with mass (inertia) will be modeled and lateranalyzed, where a clear distinction is made between small agglomerates (d < Kolmogorov length l_k) which may break up due to viscous forces and large agglomerates (d > l_k) for which the inertia forces are responsible for a possible breakage. Due to their practical relevance wall-bounded shear flows are in the focus of interest. Besides the development of a modern sustainable simulation concept, the main goal is to improve the physical understanding of the build-up of agglomerates and their potential breakage. In addition to the fluid-induced breakage of agglomerates the break-up due to particle-wall and particle-particle collisions will be included in the modeling concept, the simulation and the final analysis. At the end an overall concept for practically relevant applications will beavailable.

该项目的目标是对湍流、高负荷分散多相流中颗粒团聚的动态过程进行建模、模拟和分析。在第一个项目期间，基于四向耦合欧拉-拉格朗日方法的研究取得了重大进展，该方法依赖于描述复杂湍流的大涡模拟技术和分散相的同步粒子跟踪方案。在对粒子碰撞进行确定性处理的基础上，建立了两个新的团聚模型和一个壁面粘附模型。这些首先基于各种测试案例和广泛的参数范围进行验证，然后成功地应用于分析高负载流体湍流中的团聚过程。从而对颗粒团聚的物理关系及其最重要的影响因素以及团聚体对湍流流场的反馈有了新的认识。第二个项目期间的目标是纳入团块破碎的影响，为了简化目的，尚未考虑到这一点，但对整个过程的描述起着重要作用。在技术应用中，团聚体的生长是团聚体破碎与团聚体破碎相互作用的结果，导致了特定的粒度分布。这反过来又决定性地决定了重要的过程，如过滤器或旋风分离器的分离，药物的剂量或化学反应器中的反应速率。因此，对这两种现象的描述对于高负荷湍流两相流的真实模拟是必不可少的。从三种最重要的破碎机制的列表中，将特别注意由于流体诱导的力而引起的团块破碎。与文献中最先进的（无质量和完全小的团聚体的破碎，dns和大多数均匀各向同性湍流）不同，流体诱导的具有质量（惯性）的团聚体的破碎将被建模并稍后进行分析，其中对可能由于粘性力而破裂的小团聚体（d < Kolmogorov长度l_k）和可能由于惯性力而破裂的大团聚体（d > l_k）进行明确区分。由于其实际意义，壁面切变流是关注的焦点。除了发展现代可持续模拟概念外，主要目标是提高对团块形成及其潜在破坏的物理理解。除了流体引起的团聚体破碎外，由于颗粒-壁和颗粒-颗粒碰撞造成的破碎将包括在建模概念，仿真和最终分析中。最后，将提供实际相关应用的总体概念。