Europhys. Lett, 48 (5), pp. 475-481 (1999)
Vortex structures in dilute quantum fluids
T. Winiecki 1, J. F. McCann 2and C. S. Adams 1
1 Department of Physics, University of Durham, Rochester Building
South Road, Durham, DH1 3LE, England, UK
2 Department of Applied Mathematics and Theoretical Physics, Queen's University
Belfast, BT7 1NN, Northern Ireland, UK
(received 16 July 1999; accepted in final form 30 September 1999)
PACS. 03.75Fi - Phase coherent atomic ensembles; quantum condensation phenomena.
PACS. 47.37+q - Hydrodynamic aspects of superfluidity.
PACS. 67.40Vs - Vortices and turbulence.
Vortex structures in dilute quantum fluids are studied using the time-independent Gross-Pitaevskii equation. The velocity and momentum of vortex rings with multiple circulation are determined and their core structures analysed. For flow around a spherical object, we study the encircling and pinned ring solutions, and determine their excitation energies as a function of velocity for both penetrable and impenetrable objects. The ring and laminar flow solutions converge at a critical velocity, which decreases with increasing object size. We also study the vortex solutions associated with flow past a surface bump which indicate that surface roughness also reduces the critical velocity. This effect may have important implications for the threshold of dissipation in superfluids and superconductors.
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