Investigating the role of magnetic fields, instabilities and turbulence in fluid mixing

研究磁场、不稳定性和湍流在流体混合中的作用

• 批准号: 2606320
• 金额: --
• 依托单位: UNIVERSITY OF EXETER
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2606320
• 关键词: Investigating; role; magnetic; fields; instabilities

In hydrodynamic systems, a number of instabilities can grow from interface layers. These include two classic examples, the Rayleigh-Taylor instability, driven by gravity, and the Kelvin-Helmholtz instability, driven by shear flow. As these instabilities develop, non-linearities grow and a turbulent layer forms at the interface. A key characteristic of these layers is their growth in time which follows a self similar evolution (Zhou et al 2019).Analytically a similarity solution can be derived from the set of coupled PDEs that describe fluid motion, revealing the scaling with time for the expansion of the layer. These solutions can be extended to include further important physical complexities of the system, including modelling of density contrasts. This was performed by Hillier (2019) using a multi layer expansion which asymptotes to a model of the mean layer properties. Having a model of the mean layer properties allows important characteristics of the layer, including asymmetries and energy contained in the turbulent velocity field to be elucidated.The same linear instabilities that grow and develop the turbulent mixing layers in hydrodynamic systems also appear in magnetohydrodynamic (MHD) systems where magnetic fields and their dynamics couple with the flow. The non-linear MHD equations do permit similarity solutions, but there has only been limited work attempting to quantify how magnetic fields alter the mixing dynamics and with it the similarity solution. The key goal in this project is to develop similarity solutions in the MHD framework for interface turbulence mixing, benchmarking these solutions against 3D MHD simulations. This work can connect with turbulent mixing in industrial processes and astrophysical flows.

在水动力系统中，界面层会产生许多不稳定性。这包括两个经典的例子，由重力驱动的瑞利-泰勒不稳定性和由剪切流驱动的开尔文-亥姆霍兹不稳定性。随着这些不稳定性的发展，非线性增长，并在界面处形成湍流层。这些层的一个关键特征是它们随着时间的推移而增长，并遵循自相似的进化（Zhou et al . 2019）。从描述流体运动的耦合偏微分方程集可以导出相似解，揭示了层的膨胀随时间的缩放。这些解决方案可以扩展到包括系统更重要的物理复杂性，包括密度对比建模。这是由Hillier（2019）使用接近平均层属性模型的多层展开来完成的。平均层性质的模型允许层的重要特征，包括不对称性和包含在湍流速度场中的能量得到阐明。在流体动力系统中，生长和发展湍流混合层的线性不稳定性也出现在磁场及其动力学与流动耦合的磁流体动力系统中。非线性MHD方程确实允许相似解，但是只有有限的工作试图量化磁场如何改变混合动力学和与之相关的相似解。该项目的关键目标是在MHD框架中开发用于界面湍流混合的相似解决方案，并将这些解决方案与3D MHD模拟进行基准测试。这项工作可以与工业过程中的湍流混合和天体物理流动联系起来。