Mastering a liquid magnet

掌握液体磁铁

• 批准号: 2602988
• 金额: --
• 依托单位: University of East Anglia
• 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-2602988
• 关键词: Mastering; liquid; magnet

The ability to manipulate and control liquid surfaces and interfaces is of crucial importance in a host of different engineering and industrial applications. Typically, control is best achieved in a non-invasive manner via some external agency (e.g. an electric field or a magnetic field). Liquid surfaces are highly susceptible to instabilities and a target surface shape for a particular application can be challenging to achieve. The integrity of the surface can be easily compromised by wavelike disturbances and other surface irregularities. In this project we will investigate how to control surface shape for a ferrofluid. Motivation comes from the atomisation industry: during atomisation small toroidal-shaped liquid drops may form as part of the droplet cluster. Such drops rapidly disintegrate as a result of surface tension. The manner in which this disintegration occurs is not fully understood and experiments are complicated by the difficulty of achieving a toroidal drop as an initial condition. We will aim to show that this can be achieved by use of a ferrofluid. Such fluids contain large numbers of tiny magnetizable particles in a stable suspension and which experience a body force when exposed to a magnetic field. In essence they behave like a liquid magnet. The magnetic body force can act to stabilise a ferrofluid in surprising ways. For example, it is known that a liquid cylinder composed of a ferrofluid can be entirely stabilised when acted upon by an azimuthal magnetic field that is generated by a current-carrying wire along the axis of the liquid cylinder. Under normal circumstances such a liquid cylinder will be rapidly driven out of equilibrium and ultimately break up into droplets. The same stability may be possible for a toroidal drop; if so it would provide a means to create a controllable initial state that can be set to disintegrate at a specified time by switching off the stabilising field as required. Aims and method: The principal aims of the project will be to investigate ferrofluid surface equilibria, one example being the liquid torus, and to determine their stability. A secondary goal will be to study the propagation of disturbances (e.g. solitary waves) along these equilibrium structures. The equilibrium problem will be formulated as a coupled boundary-integral problem to determine the surface shape and static magnetic field simultaneously. This will be done numerically by some asymptotic analysis will be possible in certain limits. Once equilibria have been computed their stability will be studied via a variational formulation.

操纵和控制液体表面和界面的能力在许多不同的工程和工业应用中至关重要。通常，最好通过一些外部机构（例如电场或磁场）以非侵入方式实现控制。液体表面极易不稳定，并且特定应用的目标表面形状很难实现。表面的完整性很容易受到波状扰动和其他表面不规则性的影响。在这个项目中，我们将研究如何控制铁磁流体的表面形状。动机来自雾化行业：在雾化过程中，小环形液滴可能形成为液滴簇的一部分。这些液滴由于表面张力而迅速分解。这种崩解发生的方式尚不完全清楚，并且由于难以实现环形液滴作为初始条件，实验变得复杂。我们的目标是证明这可以通过使用铁磁流体来实现。此类流体在稳定的悬浮液中含有大量微小的可磁化颗粒，当暴露于磁场时会受到体积力。从本质上讲，它们的行为就像一块液体磁铁。磁体力可以以令人惊讶的方式稳定铁磁流体。例如，已知由铁磁流体组成的液体圆柱体在受到由沿液体圆柱体的轴线的载流线产生的方位磁场作用时可以完全稳定。在正常情况下，这样的液体圆柱体将迅速失去平衡并最终分解成液滴。环形跌落也可能具有相同的稳定性；如果是这样，它将提供一种创建可控初始状态的方法，可以通过根据需要关闭稳定场来将其设置为在指定时间分解。目标和方法：该项目的主要目标是研究铁磁流体表面平衡（其中一个例子是液体环面），并确定其稳定性。第二个目标是研究扰动（例如孤立波）沿着这些平衡结构的传播。平衡问题将被表述为耦合边界积分问题，以同时确定表面形状和静磁场。这将通过一些渐进分析在数值上完成，在某些限制下是可能的。一旦计算出平衡，将通过变分公式研究其稳定性。