Multi-scale investigation on the mobility effect of spherical and non-spherical particles as part of disperse solid/fluid systems with respect to momentum and heat exchange

作为分散固体/流体系统一部分的球形和非球形颗粒在动量和热交换方面的流动性效应的多尺度研究

• 批准号: 333932055
• 负责人: Professor Dr.-Ing. Harald Kruggel-Emden
• 金额: --
• 依托单位: Fachgebiet Mechanische Verfahrenstechnik und Aufbereitung (MVTA)
• 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/333932055?language=en
• 关键词: Multi; scale; investigation; mobility; effect

A core theme in the study of disperse solid/fluid flows is the detailed analysis of the flow field behavior and the phenomena induced by the presence of the dispersed phase. In dense particle-fluid flows an accurate description of the momentum and heat transfer between the two phases is desirable and can be derived from particle-resolved direct numerical simulations (PR-DNS). The complexity of these flows increases when particles are allowed to move, such as in fluidized beds in contrast to static particle ensembles such as packed beds. In these dynamic and dense particle systems, particle velocity fluctuations and inhomogeneities in the local particle distribution occur, which are referred to as mobility effects. Very recent studies have shown that mobility effects have a non-negligible influence on momentum and heat transfer of spherical particles, but a rigorous inclusion into correlations is still lacking, which is even more the case for non-spherical particles and coupled heat transfer. The objective of the proposed research work is to contribute to a broader base of PR-DNS data for gas/solid flows involving heat transfer, where particles are allowed to move freely. The PR-DNS serve to derive correlations for momentum and heat transfer that rigorously take into account mobility effects over a wide range of parameters (Reynolds number, Stokes number, solid volume fraction) for the first time. The key novelty of these new correlations will be the computation of momentum and heat transfer based on a per particle basis using relative particle position and velocity information, for which both, a physics based kernel smoothing approach and an approach based on an artificial neural network, are applied. Thereby, transversal particle/fluid forces arising from the local flow around individual particles are also inherently captured, which are insufficiently described by existing volume-averaged models. In order to quantify the benefit of the new correlations over conventional correlations, we will perform fluidized bed simulations involving heat transfer using the unresolved DEM-CFD approach and the PR-DNS approach. By comparing the simulations with respect to integral parameters, we will be able to assess the importance of considering mobility effects. In the second part of the project, we repeat this procedure for particle-fluid flows involving selected non-spherical particles (sphero-cylinder, cube, oblate). These simulations will allow insights into the relationship between particle shape and particle mobility effects for the first time and will pave the way for more accurate closures additionally taking into account the aspericity.

分散固体/流体流动研究的一个核心主题是详细分析流场行为和由分散相的存在引起的现象。在密集的颗粒流体流动中，需要精确描述两相之间的动量和热量传递，并且可以从颗粒分解直接数值模拟（PR-DNS）中得到。当颗粒被允许移动时，这些流动的复杂性增加了，例如在流化床中，与静态颗粒集合相比，如填充床。在这些动态和密集的粒子系统中，粒子速度波动和局部粒子分布的不均匀性被称为迁移率效应。最近的研究表明，迁移率效应对球形粒子的动量和传热有不可忽略的影响，但仍然缺乏严格的关联，特别是对非球形粒子和耦合传热的情况。拟议的研究工作的目标是为涉及热传递的气体/固体流动提供更广泛的PR-DNS数据基础，其中颗粒可以自由移动。PR-DNS首次用于推导动量和传热的相关性，该相关性严格考虑了大范围参数（雷诺数、斯托克斯数、固体体积分数）的迁移率效应。这些新关联的关键新颖性将是基于使用相对粒子位置和速度信息的每个粒子基础计算动量和传热，为此，应用了基于物理的核平滑方法和基于人工神经网络的方法。因此，由单个粒子周围的局部流动引起的横向粒子/流体力也固有地被捕获，这是现有的体积平均模型无法充分描述的。为了量化新关联相对于传统关联的好处，我们将使用未解析的DEM-CFD方法和PR-DNS方法进行涉及传热的流化床模拟。通过比较积分参数的模拟，我们将能够评估考虑迁移效应的重要性。在项目的第二部分，我们对涉及选定的非球形颗粒（球柱、立方体、扁圆形）的颗粒流体流动重复此过程。这些模拟将使我们第一次深入了解颗粒形状和颗粒迁移效应之间的关系，并将为考虑到粗糙度的更精确的封闭铺平道路。