Counterflow turbulence (PhD)

Supervisors: Andrew Baggaley
Relevant research groups: Fluids

The two-fluid model of superfluid helium was invented by Tisza & Landau in the late 1930s to account for the remarkable flow properties of liquid helium at very low temperatures. These properties include the fluid’s ability to perfectly conduct heat and to flow without friction, superfluidity. Counterflow is a mechanism of heat conduction in these special fluids, in which the counterflow of two fluids prevents the formation of any localised "hot spots" ( hence bubbles don’t form in boiling liquid helium below 2.17 Kelvin). This (apparently) ideal heat transfer makes liquid helium very useful to engineers: lacking any other usable fluid (below 4 K, all other materials freeze), liquid helium can cool many important devices, from infrared detectors on board orbiting satellites, to the powerful superconducting magnets that accelerate elementary particles or that form the heart of medical imaging equipment. However above a certain critical velocity the smooth laminar flow of the superfluid component transitions into into a disordered tangle of quantized vortex filaments, which dissipate kinetic energy. A number of important open questions are outstanding in this turbulent regime and we would aim to address some of these questions in this project.

Two-fluid turbulence at low temperatures (PhD)

Supervisors: Andrew Baggaley
Relevant research groups: Fluids

Nearly every fluid in the universe is affected by turbulence, from the flow of blood in your body, clouds in the atmosphere, and the interstellar medium in the galaxy. Although our understanding of the nature of turbulence is improving, we are a long way from a full understanding of the random, chaotic motion of these liquids and gases. Part of the problem is that although we commonly think of turbulence as being a collection of vortices or eddies, in a classical fluid such as water or air these vortices are not well defined elements. However at very low the weirdness of quantum mechanics changes the game. The fluid loses its friction and rotational motion in the fluid is constrained to thin well defined quantised vortices, mini tornadoes, which thread through the fluid. This project would investigate the coupling between the normal and superfluid components of liquid helium, when both fluids are driven into a turbulent state. We would aim to model experiments taking place in Grenoble and Prague, and disseminate our work at leading international conferences.

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