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Mathematical modelling of selected problems in cryogenic fluid mechanics
Hodic, Jan ; La Mantia, Marco (advisor) ; Schmoranzer, David (referee)
The dynamics of low-temperature fluids, such as superfluid helium 4, is an open scientific problem. The experimental study of similarities and differences between quantum (superfluid) and classical (viscous) flows is specifically an active research field, which already led to significant progress in our phenomenological understanding of the underlying physics. It also revealed that a comprehensive theoretical description is still missing, as, for example, in the case of the observed behaviour of moving bodies in quantum flows. The work aim is to derive the existence theory for the weak solution of a relevant system of equations based on the Landau model of superfluid helium 4 and appropriate numerical schemes to solve these equations.
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Visualization of liquid Helium flows generated by an oscillating rectangular cylinder
Švančara, Patrik ; La Mantia, Marco (advisor) ; Jackson, Martin James (referee)
For the first time, a cylinder of rectangular cross section, performing quasi-harmonic oscillations in liquid helium, was employed for the experimental study of the dynamics of macroscopic vortex structures shed at the sharp edges of the obstacle. The flow of liquid helium was visualized by the motion of small, solidified deuterium particles, dispersed in the experimental cell and illuminated by a thin laser sheet. Experiments in He I, a classical viscous fluid, and He II, a fluid displaying superfluidity, showed, at low frequencies of the oscillating body, a significant difference in the flow, possibly due to the much larger heat conductivity of He I, compared to He I. At large frequencies, the flows appeared instead to be similar, which agrees with the current understanding of quantum flows, at large enough length scales. Powered by TCPDF (www.tcpdf.org)
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