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

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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).