The Magnetohydrodynamics of Liquid Metal Tornadoes (MAGNADO)

液态金属龙卷风的磁流体动力学 (MAGNADO)

• 批准号: EP/X034402/1
• 负责人: Susanne Horn
• 金额: $ 161.88万
• 依托单位: Coventry University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FX034402%2F1
• 关键词: Magnetohydrodynamics; Liquid; Metal; Tornadoes; MAGNADO

The self-excitation of large-scale magnetic fields through fluid motion in the metallic interiors of planets is one of the most challenging problems in fluid dynamics. This so-called dynamo process is powered by turbulent rotating convection and involves a complex feedback cycle between the flow and the induced electrical currents. Because planetary dynamos are inaccessible to direct observation and numerical simulations cannot reach the extreme conditions prevailing deep inside planets, we need strongly theoretical-physics driven approaches to elucidate the underlying flow mechanisms and make meaningful and accurate predictions. The aim of the research proposed here is to study rotating magnetoconvection with the novel inclusion of centrifugal buoyancy. Centrifugal buoyancy promotes the formation of large-scale tornado-like vortices. I hypothesise that these tornadoes are favourable for dynamo action: Their inherent nature is helical, breaks mirror-symmetry, thus, resembling the classical theoretical Ponomarenko dynamo model. Additionally, flow speeds well above the free-fall limit can be generated. Direct numerical simulations (DNS) in liquid metals will be central for finding the sweet spot for tornado formation and dynamo action. But pushing the parameters to an extreme is not the solution for this endeavour. Instead, an understanding of the interconnected nonlinear dynamics of these highly turbulent thermal-inertial magnetohydrodynamic flows is required. To this end, successively more complex forms of the induction equation will be considered. Corresponding DNS and experiments in liquid gallium and sulfuric acid will provide a detailed picture of the local planetary induction and dynamo processes. The project shall culminate in an accurate forward model of an analogous convection-driven fluid dynamo device that is also realisable on a laboratory scale, which was previously thought impossible.

通过行星金属内部的流体运动产生大尺度磁场的自激是流体动力学中最具挑战性的问题之一。这种所谓的发电机过程由湍流旋转对流提供动力，并涉及流动和感应电流之间的复杂反馈循环。由于行星发电机无法直接观察，并且数值模拟无法达到行星内部普遍存在的极端条件，因此我们需要强大的理论物理驱动方法来阐明潜在的流动机制并做出有意义且准确的预测。这里提出的研究的目的是研究具有离心浮力的新颖的旋转磁对流。离心浮力促进了大规模龙卷风状涡流的形成。我假设这些龙卷风有利于发电机作用：它们的固有性质是螺旋形的，打破镜像对称性，因此类似于经典理论波诺马连科发电机模型。此外，可以产生远高于自由落体极限的流速。液态金属中的直接数值模拟（DNS）对于寻找龙卷风形成和发电机作用的最佳点至关重要。但将参数推向极端并不是这一努力的解决方案。相反，需要了解这些高度湍流热惯性磁流体动力流的相互关联的非线性动力学。为此，将考虑归纳方程的相继更复杂的形式。相应的 DNS 以及液态镓和硫酸实验将提供局部行星感应和发电机过程的详细图片。该项目最终将形成一个类似对流驱动流体发电机装置的精确正演模型，该模型也可以在实验室规模上实现，这在以前被认为是不可能的。