Interaction of turbulent superfluid helium with solid walls in the zero temperature limit

1. 该项目的主要目的是通过实验确定，并从理论上理解，在零温度极限下，固体壁对移动的湍流超流体施加的摩擦力的值。目的：-设计并制造一种测量管内流动超流体压降的实验装置；-在温度为0.1K的稀释冰箱中测试、校准并进行本实验；-开发和验证一个数值模型，以模拟微观粗糙固体壁附近量子化涡线的动力学；-运行和分析受施加超流体流动影响的两个平行壁面之间涡缠结的数值模拟。2. 学生将学习实验低温技术，超流体湍流理论和模拟超流体动力学的数值方法。在实验方面，他将在现有的稀释冰箱上设计和设置实验装置，测试和运行实验，并分析结果数据。在数值上，他将修改现有的粗糙固体壁面附近涡线的数值代码，验证数值方法的分析与解析模型的期望，并进行湍流超流体流过粗糙固体壁面的模拟和分析。量子湍流是低温研究的一个积极发展方向。到目前为止，还没有关于壁面施加在运动的湍流超流体上的摩擦力值的实验和理论资料。只有间接证据表明，在大约0.7K以下，这种力变得非常小。对于理解容器中湍流超流体的性质和预测其行为的任何进展，找到这些信息是绝对必要的。任何结果都将标志着量子湍流研究的突破。EPSRC的相关研究领域是低温物理（超流体、量子湍流、低温）。

1. The main aim of the project is to determine experimentally, and to understand theoretically, the value of friction force exerted by a solid wall on a moving turbulent superfluid in the zero-temperature limit. Objectives:- to design and build an experimental apparatus to measure the pressure drop along a pipe with flowing superfluid 4He;- to test, calibrate and conduct this experiment in a dilution refrigerator at temperature 0.1K;- to develop and validate a numerical model to simulate the dynamics of quantized vortex lines near a microscopically-rough solid wall;- to run and analyze numerical simulations of vortex tangles between two parallel walls subject to an imposed superfluid flow. 2. The student will learn experimental low-temperature techniques, the theory of superfluid turbulence and numerical methods for modelling superfluid dynamics. Experimentally, he will design and set-up the experimental apparatus on an existing dilution refrigerator, test and run the experiment, and analyze the resulting data. Numerically, he will modify an existing numerical code vortex lines near rough solid walls, validate the analysis of the numerical method against the expectations from analytical models, and conduct and analyze simulations of turbulent superfluid flowing past a rough solid wall.3. Quantum Turbulence is an actively developing direction of low-temperature research. As yet, no experimental and theoretical information on the value of the friction force exerted by a wall on a moving turbulent superfluid is available. There are only circumstantial evidences that, below circa 0.7K, this force becomes pretty small. For any progress in understanding the properties, and predicting behavior of turbulent superfluid in a container, it is absolutely necessary to find obtain this information. Any result will manifest a breakthrough in the research on Quantum Turbulence.The relevant EPSRC research area is Low Temperature Physics (superfluidity, quantum turbulence, cryogenics).