Numerical Modeling of Phase Change Phenomena in Particulate Flows

颗粒流中相变现象的数值模拟

• 批准号: RGPIN-2014-06008
• 负责人: Nikrityuk, Petr
• 金额: $ 1.82万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=611973
• 关键词: Numerical; Modeling; Phase; Change; Phenomena

The main objective of this research project consists in gaining a fundamental understanding of the behaviour of phase-change phenomena in particulate flows under the influence of gravity. This understanding will help to design novel technologies in metallurgical and applied materials engineering, e.g. such as casting high-temperature resistant alloys, which go on to help save energy and protect the environment. It is well known that the classical multiphase model (Euler-Euler) often fails to predict a gravity-driven solidification of multicomponent materials. In view of this, an alternative approach such as the Euler-Lagrange model can be used to adequately forecast solidification/melting processes occurring during casting of metal alloys. In this approach the motion of the solid particles is treated individually using Newton’s law of motion. So far, however, Euler-Lagrange-based models for phase-change-related problems have met with little attention in the literature, even though they might provide great potential for reliable numerical simulations of such complex flows including phase-change effects. The proposed research focuses on the following aims: 1. Development and validation of an Euler-Lagrange model for particulate flows with phase-change effects, where the particles undergoing the phase change are modelled using the three-dimensional (3D) discrete element model (DEM) formulated in Lagrangian space, while the liquid phase is simulated using a computational fluid dynamics (CFD)-based model formulated in Eulerian space. 2. Development of subgrid models for interfacial heat and mass transfer applied to moving particles undergoing phase change. These models serve as a coupling between DEM and CFD models. 3. Validation of numerical models against experiments carried out for a defined reference system under well-defined boundary conditions: this is the melting of ‘ice’ particles settling in water. Here the Direct Numerical Simulation (DNS) of existing ‘ice’ experiments are planned to validate subgrid models for interfacial heat and mass transfer between solid and liquid phases. 4. Investigation of the phase distribution and flow anomalies in the liquid phase, such as the interplay between buoyancy and Archimedes forces in dependence on the volume fraction of solid. The vision followed by the project in the long-term consists in the development of an Euler-Lagrange model for a numerical simulation of binary alloy (AlSi) columnar-equiaxed solidification. To reach this goal it is necessary to understand the ruling principles of the melting (solidification) of solid particles moving in the liquid phase. Recent experimental studies published in the literature show that special attention should be paid to explaining anomalies relating to interaction between the gravity-induced forces. The short-term goal of this project is to develop and validate a subgrid semiempirical model for the behaviour of solidifying/melting particles depending on specific nondimensional numbers such as the Archimedes number (Ar), the Grashof number (Gr) and the Stefan number (Ste). The project's success will help advance knowledge on the fundamentals of solidification and on the accurate forecast of multicomponent material properties. The practical significance of this research consists in the development and validation of simplified models describing the interfacial heat and mass transfer between solid and liquid phases undergoing phase changes. The models developed in this project will contribute to a significant improvement in the computational software used in the industry to improve processes, reducing the production costs of advanced materials in Canada.

这一研究项目的主要目的在于从根本上了解在重力影响下颗粒流中相变现象的行为。这一认识将有助于设计冶金和应用材料工程中的新技术，例如铸造耐高温合金，这些技术将继续有助于节约能源和保护环境。众所周知，经典的多相模型(Euler-Euler)往往无法预测重力驱动的多组分材料的凝固过程。有鉴于此，另一种方法，如欧拉-拉格朗日模型，可以用来充分预测金属合金铸造过程中的凝固/熔化过程。在这种方法中，固体粒子的运动是用牛顿运动定律单独处理的。然而，到目前为止，基于欧拉-拉格朗日模型的相变相关问题在文献中很少受到关注，尽管它们可能为包括相变效应在内的这种复杂流动的可靠数值模拟提供巨大的潜力。拟议的研究侧重于以下目标： 1.发展和验证了具有相变效应的颗粒流的欧拉-拉格朗日模型，其中经历相变的颗粒使用在拉格朗日空间中建立的三维(3D)离散元模型(DEM)来模拟，而液体相使用在欧拉空间中建立的基于计算流体力学(CFD)的模型来模拟。 2.建立了适用于相变运动颗粒界面热质传递的亚网格模型。这些模型是DEM和CFD模型之间的耦合。 3.在明确的边界条件下，通过对已定义的参照系进行的实验，对数值模型进行验证：这是在水中沉淀的“冰”颗粒的融化。在这里，计划对现有的冰实验进行直接数值模拟(DNS)，以验证固-液两相之间界面热质传递的亚格子模型。 4.研究了液体中的相分布和流动异常，如浮力和阿基米德力之间的相互作用与固体体积分数的关系。 该项目的长期愿景包括开发用于数值模拟二元合金(AlSi)柱状等轴凝固的欧拉-拉格朗日模型。为了达到这一目标，有必要了解固体颗粒在液体中运动的熔化(凝固)的支配原理。最近发表在文献中的实验研究表明，应特别注意解释与重力诱导力之间相互作用有关的异常。该项目的短期目标是开发和验证一个关于凝固/熔化粒子行为的亚格子半经验模型，该模型依赖于特定的无量纲数，例如阿基米德数(Ar)、格拉肖夫数(Gr)和斯特凡数(Ste)。该项目的成功将有助于增进对凝固基本原理的了解，以及对多组分材料性能的准确预测。这项研究的实际意义在于开发和验证描述相变过程中固、液两相之间界面热质传递的简化模型。在该项目中开发的模型将有助于显著改进行业中用于改进工艺的计算软件，从而降低加拿大先进材料的生产成本。