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Visualising Superfluid Turbulence Using an Immiscible Second Component

使用不混溶的第二分量可视化超流体湍流

基本信息

批准号：
EP/X028518/1
负责人：
Ryan Doran
金额：
$ 37.48万
依托单位：
Newcastle University
依托单位国家：
英国
项目类别：
Fellowship
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%2FX028518%2F1
关键词：
Visualising Superfluid Turbulence Using Immiscible

项目摘要

While the dynamics of gases which occupy the majority of the universe are dominated by billiard ball-like collisions between particles, at temperatures which are less than a millionth of a degree above absolute zero quantum mechanics takes over. Here, a class of particles called bosons cease to behave like individual particles. Rather than bouncing off each other, the millions of bosons present enter the same quantum state, and behave as one, single, giant wave of matter. This quantum fluid has several remarkable properties, including its ability to flow without viscosity.Quantum fluids are an active area of research, with hundreds of state-of-the-art laboratories around the world creating and studying quantum fluids. The main advantage of quantum fluids is that, due to their high degree of experimental control (experimentalists are able to precisely tune the fluid's physical properties and manipulate it in time and space), they are a "clean" way to realise a many-particle quantum system, giving rich insight into the quantum world. Quantum fluids can also be used as a testbed for complicated physical phenomena such as superconductors, black holes, and the Big Bang. They also offer access to new physical regimes of fluid dynamics, the ability to study broader topics in turbulence, and the potential to solve challenges in imaging quantum fluid flows.Just like in classical fluid, it is possible to have turbulence in quantum fluids, although the physics behind this turbulence are subtly different. In classical fluids, a vortex can have an arbitrary size and strength - from the whirlpool created when you empty the bath, to the red spot of Jupiter. In quantum fluids, on the other hand, vortices have a fixed quanta of circulation and a fixed vortex core size, forming a point in 2D, or a vortex filament in 3D. These quantum vortices are the building blocks of turbulence in quantum fluids; in large systems which are driven out of equilibrium, turbulence manifests itself as many vortices arranged in a complex tangle. Unfortunately it is difficult to visualise the flow of quantum fluids, since line-of-sight imaging can't be used to image a complex distribution of tangled vortices in 3D. While in classical fluids small particles can be traced by ultra-fast cameras providing snapshots of the flow, these particles are much larger than the size of a quantum vortex. As a result, the particles alter the dynamics of the fluid, suppressing turbulence, and obscuring the flow that they are attempting to visualise.It is also possible to create a mixture of quantum fluids. This mixture may be miscible (where the two constituent fluids form a homogeneous mixture) or immiscible (where it is energetically unfavourable for the fluids to overlap), like oil and water. In the immiscible regime, if one of the fluids is heavily populated (the majority fluid) and the other is weakly populated (the minority fluid) , the minority fluid will in-fill the vortex cores of the majority fluid. This provides a potential route to tracing the vortices in the majority fluid, however changing properties of the minority fluid (such as adding more particles to this fluid) can modify the properties of the vortex, suggesting new regimes of vortex dynamics and turbulence. The aim of this fellowship is to explore the nature of immiscible quantum fluids across a range of length scales. I will build up from the microscopic scale of one or a few vortices (dynamics of vortex pairs and vortex nucleation in 2D, vortex reconnections and Kelvin wave cascades in 3D) to macroscopic systems of many vortices (Onsager vortex formation in 2D, quantum turbulence in 2D and 3D). The relevance of these results to current state-of-the-art experiments will be enhanced by collaborations with world leading experimentalists, while predictions on potential flow visualisation applications will inform future cold atom experiments.

虽然占据宇宙大部分区域的气体的动力学主要是粒子之间类似台球的碰撞，但在绝对零度以上不到百万分之一度的温度下，量子力学占据了主导地位。在这里，一类被称为玻色子的粒子不再像单个粒子那样表现。在场的数以百万计的玻色子不是相互反弹，而是进入相同的量子状态，表现为一个单一的巨大物质波。这种量子流体具有几个显著的性质，包括它可以在没有粘性的情况下流动。量子流体是一个活跃的研究领域，世界各地有数百个最先进的实验室创建和研究量子流体。量子流体的主要优势是，由于它们高度的实验控制性(实验者能够精确地调整流体的物理性质，并在时间和空间上操纵它)，它们是实现多粒子量子系统的一种“干净”的方式，使人们能够对量子世界有丰富的洞察力。量子流体也可以用作复杂物理现象的试验台，如超导体、黑洞和大爆炸。它们还提供了对流体动力学新的物理状态的访问，能够研究湍流中更广泛的主题，并有可能解决量子流体流动成像中的挑战。就像在经典流体中一样，量子流体中可能存在湍流，尽管这种湍流背后的物理原理略有不同。在经典流体中，漩涡可以有任意的大小和强度--从你倒空浴缸时产生的漩涡，到木星的红色斑点。另一方面，在量子流体中，涡旋具有固定的循环量和固定的涡核大小，在2D中形成一个点，或者在3D中形成涡丝。这些量子涡旋是量子流体中湍流的基石；在被驱使失去平衡的大系统中，湍流表现为许多涡旋排列成一个复杂的纠缠。不幸的是，很难可视化量子流体的流动，因为视线成像不能用来在3D中成像复杂的纠缠涡旋分布。虽然在经典流体中，小颗粒可以通过提供流动快照的超高速相机来跟踪，但这些颗粒比量子涡旋的大小要大得多。结果，这些粒子改变了流体的动力学，抑制了湍流，遮挡了它们试图看到的流动。也有可能创造出量子流体的混合物。这种混合物可以是可混溶的(其中两种组成的流体形成均匀的混合物)，也可以是不混溶的(在能量上不利于流体重叠的地方)，如油和水。在非混相区，如果其中一种流体填充较多(主要流体)，而另一种流体填充较弱(少数流体)，少数流体将填充大多数流体的涡核。这为追踪大多数流体中的涡旋提供了一条潜在的途径，然而，少数流体的性质的改变(如向该流体中添加更多的粒子)可能会改变涡旋的性质，从而提出了新的涡旋动力学和湍流区域。这项研究的目的是在一定的长度范围内探索不相容量子流体的性质。我将从一个或几个涡旋的微观尺度(2D涡对和涡核的动力学，3D涡重连和开尔文波级联)到多个涡旋的宏观系统(2D的Onsager涡旋形成，2D和3D的量子湍流)。这些结果与当前最先进的实验的相关性将通过与世界领先的实验学家的合作而得到加强，而对潜在流动可视化应用的预测将为未来的冷原子实验提供信息。