Visualization of quantum turbulence in superfluid helium in the zero-temperature limit

该项目的目的是首次观察到超流氦中单个涡旋线在如此低的温度下发生的重新连接和变形，以至于几乎没有正常的流体。该项目将产生不同类型湍流中的涡旋线、涡旋束和涡旋的图像，通过氦准分子或染色纳米颗粒作为示踪剂的荧光来可视化。为了实现这一点，将开发一种新的技术，利用这种技术，人们可以用氦准分子或染色的纳米颗粒播种涡旋线，并在激光诱导下拍摄它们的荧光图像。正在研究中的装有超流氦的容器将位于能够冷却到0.1K以下并连续旋转的低温恒温器内。这名学生将开发(I)制造准分子和超流氦光学元件的注射器，(Ii)激光诱导荧光，(Iii)极低强度光的成像；他将参与运行低温恒温器，自动化数据采集和分析，撰写和展示结果。该项目属于EPSRC的量子流体和固体研究领域，但也影响流体动力学和空气动力学。它将实现一种新的低温可视化方法，涉及捕获在量子化涡旋线上的示踪粒子，并将展示该方法在量子湍流研究中的潜力。由于量子湍流在大尺度上模拟了经典湍流，我们对集中涡度区域结构和动力学的直接可视化也可能对理解经典湍流中涉及大振幅涡旋的罕见事件做出重要贡献。

The aim of the project is to observe for the first time reconnections and deformations occurring with individual vortex lines in superfluid helium at temperatures so low that there is practically no normal fluid. The project will result in images of vortex lines, their bundles and tangles in different types of turbulent flow, visualized through fluorescence of either helium excimers or dyed nanoparticles as tracers. To achieve this, a novel technique will be developed with which one can seed vortex lines by either helium excimers or dyed nanoparticles and take images of their fluorescence, induced by a laser light. The container with superfluid helium under study will be located inside a cryostat capable of cooling below 0.1K and rotating continuously. The student will be developing the techniques of (i) making injectors of excimers and optical cells for superfluid helium, (ii) laser-induced fluorescence, (iii) imaging of very low-intensity light; he will be involved in running the cryostat, automating data acquisition and analysis, writing-up and presenting the results.The project belongs to the EPSRC research area Quantum Fluids and Solids, but also impacts on Fluid Dynamics and Aerodynamics. It will implement a novel method of visualization at low temperature, involving tracer particles trapped on quantized vortex lines, and will demonstrate the potential of this method for research on quantum turbulence. As quantum turbulence mimics classical turbulence on large length scales, our direct visualization of the structure and dynamics of the region of concentrated vorticity might also make an important contribution to the understanding of rare events involving vortices of large amplitude in classical turbulence.