Questions related to the oscillatory flow of He II through a grid at low temperatures

The flow of pure He II at low temperatures and a range of pressures is probed using an electrostatically-driven oscillating grid. With increasing oscillation amplitude, a (history dependent) first threshold is reached where the initially pure superflow abruptly changes: the resonant frequency decrea...

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Bibliographic Details
Published in:Journal of low temperature physics 2005-02, Vol.138 (3-4), p.543-548
Main Authors: HENDRY, P. C, MCCLINTOCK, P. V. E, NICHOL, H. A, SKRBEK, L, VINEN, W. F
Format: Article
Language:English
Subjects:
Boson degeneracy and superfluidity of 4he
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Physics
Quantum fluids and solids
liquid and solid helium
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Summary:The flow of pure He II at low temperatures and a range of pressures is probed using an electrostatically-driven oscillating grid. With increasing oscillation amplitude, a (history dependent) first threshold is reached where the initially pure superflow abruptly changes: the resonant frequency decreases and the response becomes strongly nonlinear, attributable to quantized vortices responding to the motion of the grid so as to increase its effective mass without additional damping. On further increase of oscillation amplitude a second threshold is reached, probably marking the onset of superfluid turbulence. The increase in effective mass is believed to be due to a boundary layer of vortex loops that can evolve into turbulent flow at the second threshold. Open questions and problems for future research are formulated.
ISSN:0022-2291
1573-7357
DOI:10.1007/s10909-005-2254-7