Long time vortex tangle decay in superfluid helium
- Max-Planck-Institut fuer Stroemungsforschung, Goettingen (Germany)
- Univ. of Warsaw (Poland)
Superfluid helium exhibits an unusual large heat conductivity, which however is restricted by the appearance of quantized vortex lines, the so-called superfluid turbulence. Recently, the observation of the free decay of this superfluid turbulence in large channels revealed some interesting peculiarities which can not be solely explained by the Vinen-Schwarz vortex line density evolution equation. Systematic measurements of the vortex line density in a large counterflow channel of 3 cm{sup 2} cross sectional area were carried out by determine the temporal evolution of the temperature gradient along the channel corresponding to a given heat flux. In addition the resonator quality of the channel for second-sound resonances transverse to the main flow direction was measured. In particular the existence of an initial time range where the decay is primarily governed by the dynamics of the vortex tangle, and a long time behavior, where the normal fluid viscosity is of importance could be detected. The mechanism of vortex decay in these two ranges is explained in terms of coupled superfluid and normal fluid turbulence. The key idea is that after the heat load is switched off only the average counterflow velocity vanishes, whereas appreciable velocity fluctuations remain. A criterion for the critical vortex line density L{sub c} when the vortex tangle turns into the new state of slow decay is deduced from comparing scales of classical and superfluid turbulence.
- OSTI ID:
- 47831
- Report Number(s):
- CONF-930703-; TRN: 95:011358
- Resource Relation:
- Conference: International cryogenic materials conference (ICMC), Albuquerque, NM (United States), 12-16 Jul 1993; Other Information: PBD: 1994; Related Information: Is Part Of Advances in cryogenic engineering, Volume 39, Part B; Kittel, P. [ed.]; PB: 1053 p.
- Country of Publication:
- United States
- Language:
- English
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