Transport Properties of Incompressible Field-Guided MHD Turbulence

不可压缩场引导 MHD 湍流的输运特性

• 批准号: EP/M004546/1
• 负责人: Joanne Mason
• 金额: $ 12.77万
• 依托单位: UNIVERSITY OF EXETER
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FM004546%2F1
• 关键词: Transport; Properties; Incompressible; Field; Guided

As a flow moves, it carries fluid from one location to another. In this way, a tiny parcel of fluid gradually wanders away from its initial position. In the fluid dynamics laboratory, this can be visualised by injecting dye with a syringe at a specified point in the flow. If dye is continuously released then one can trace the dye's trajectory. Instead, if at a specific point in time a small patch of fluid is dyed, then one can then study the rate of spreading of the patch. The transport of a passive contaminant in a turbulent (disordered) flow is a topic that is widely studied in fluid dynamics research and the topic can have great relevance to our everyday lives, especially when the contaminant represents an industrial pollutant dispersing in the Earth's atmosphere, viruses that can pose threats to our immune systems, or volcanic ash that can disrupt flight schedules for weeks. In magnetohydrodynamic (MHD) turbulence, transport studies are concerned with electrically conducting flows that interact with magnetic fields. Gaining knowledge of the fundamental properties of such flows is necessary in order to understand how geomagnetic storms behave (these can disrupt communication and navigation satellites and cause black outs in power grids) and how instabilities develop in laboratory plasma experiments studying magnetic confinement fusion for clean energy production purposes. Progress with understanding such complicated physical systems relies, first and foremost, on establishing a solid theoretical foundation for more simplified mathematical models. While there are a number of physical situations in which it is important to be able to understand turbulent transport in magnetised plasmas, it is also the case that applied mathematicians can learn a great deal about the fundamental dynamics and structure of an electrically conducting flow by studying its transport properties. It is this particular aspect of turbulent transport that motivates our proposed work.Over recent years, significant progress has been made with the fundamental theory of MHD turbulence. The success is largely a result of a massive increase in computational power that has enabled a series of high-resolution numerical simulations to be performed. The numerical results have been used to test competing theoretical predictions and the findings have spawned many new avenues of research. Of particular interest is the discovery of the intricate highly-aligned structure that field-guided MHD turbulence takes. Herein we propose to further our investigations into this intriguing structure and its effects. Through a series of high-resolution numerical simulations and theoretical studies of MHD turbulence, we will study the efficiency of transport by monitoring the trajectories of tracer particles. We anticipate that the our results will provide important information for developing a comprehensive phenomenological model of strong field-guided MHD turbulence, for designing future numerical simulations of plasma turbulence, and ultimately for interpreting observations and experiments.

当流动时，它将流体从一个位置带到另一个位置。这样，一个微小的流体块就逐渐偏离了它的初始位置。在流体动力学实验室中，这可以通过在流动中的指定点处用注射器注射染料来可视化。如果染料持续释放，那么可以追踪染料的轨迹。相反，如果在特定的时间点，一小块流体被染色，那么人们就可以研究该块的扩散速率。被动污染物在湍流（无序）流中的传输是流体动力学研究中广泛研究的主题，该主题与我们的日常生活密切相关，特别是当污染物代表在地球大气中分散的工业污染物时，病毒可能对我们的免疫系统构成威胁，或者火山灰可能会扰乱飞行计划数周。在磁流体动力学（MHD）湍流中，输运研究涉及与磁场相互作用的导电流。为了了解地磁暴的行为方式（这些风暴可能会破坏通信和导航卫星，并导致电网停电）以及为清洁能源生产目的研究磁约束聚变的实验室等离子体实验中的不稳定性是如何发展的，有必要了解这种流动的基本性质。理解如此复杂的物理系统的进展首先依赖于为更简化的数学模型建立坚实的理论基础。虽然有一些物理情况下，它是重要的是能够理解在磁化等离子体湍流输运，它也是应用数学家可以学习大量的基本动力学和导电流的结构，通过研究其输运性质的情况。近年来，MHD湍流的基本理论研究取得了重大进展。这一成功在很大程度上是计算能力大幅提高的结果，这使得一系列高分辨率的数值模拟得以执行。数值结果已被用于测试竞争的理论预测，这些发现催生了许多新的研究途径。特别令人感兴趣的是发现了场引导的MHD湍流所具有的复杂的高度对准的结构。在此，我们建议进一步研究这个有趣的结构及其影响。通过对MHD湍流的一系列高分辨率数值模拟和理论研究，我们将通过监测示踪粒子的轨迹来研究输运效率。我们预计，我们的研究结果将提供重要的信息，发展一个全面的唯象模型的强场引导MHD湍流，设计未来的数值模拟等离子体湍流，并最终解释观测和实验。

项目成果

Influence of a large-scale field on energy dissipation in magnetohydrodynamic turbulence

• DOI: 10.1093/mnras/stx611
• 发表时间: 2017-03
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: V. Zhdankin;S. Boldyrev;J. Mason