Spatial distribution of vortices and metastable states in rotating He II

Mathieu, P.; Maréchal, Justine; Simon, Y.

doi:10.1103/physrevb.22.4293

Cited by 18 publications

(15 citation statements)

References 14 publications

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“…For example, experiments have found a significant difference between the number of vortices obtained when the fluid is spun up to when it is spun down [15]. Reproducible hysteresis loops were measured by minimizing the mechanical and thermal noise of the apparatus [16]. Jones et al [17] attempted to explain this effect by using a principle of local momentum conservation.…”

Section: Introductionmentioning

confidence: 99%

Hysteresis effects in rotating Bose-Einstein condensates

Jackson

Barenghi

2006

Phys. Rev. A

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We study the formation of vortices in a dilute Bose-Einstein condensate confined in a rotating anisotropic trap. We find that the number of vortices and angular momentum attained by the condensate depends upon the rotation history of the trap and on the number of vortices present in the condensate initially. A simplified model based on hydrodynamic equations is developed, and used to explain this effect in terms of a shift in the resonance frequency of the quadrupole mode of the condensate in the presence of a vortex lattice. Differences between the spin-up and spin-down response of the condensate are found, demonstrating hysteresis phenomena in this system.Comment: 16 pages, 7 figures; revised after referees' report

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Section: Introductionmentioning

confidence: 99%

Hysteresis effects in rotating Bose-Einstein condensates

Jackson

Barenghi

2006

Phys. Rev. A

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“…However, it has not been detected conclusively in experiments (Northby & Donnelly 1970;Mathieu, Marechal & Simon 1980). It is unclear how to treat this boundary layer numerically within HVBK theory, which assumes a high density of vortices, so we do not consider it further in this paper.…”

Section: Boundary Conditions For V Nmentioning

confidence: 97%

Superfluid spherical Couette flow

et al. 2008

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We solve numerically for the first time the two-fluid Hall-Vinen-BekarevichKhalatnikov (HVBK) equations for an He-II-like superfluid contained in a differentially rotating spherical shell, generalizing previous simulations of viscous spherical Couette flow (SCF) and superfluid Taylor-Couette flow. The simulations are conducted for Reynolds numbers in the range 1 × 10 2 6 Re 6 3 × 10 4 , rotational shear 0.1 6 Ω/Ω 6 0.3, and dimensionless gap widths 0.2 6 δ 6 0.5. The system tends towards a stationary but unsteady state, where the torque oscillates persistently, with amplitude and period determined by δ and Ω/Ω. In axisymmetric superfluid SCF, the number of meridional circulation cells multiplies as Re increases, and their shapes become more complex, especially in the superfluid component, with multiple secondary cells arising for Re > 10 3 . The torque exerted by the normal component is approximately three times greater in a superfluid with anisotropic Hall-Vinen (HV) mutual friction than in a classical viscous fluid or a superfluid with isotropic Gorter-Mellink (GM) mutual friction. HV mutual friction also tends to 'pinch' meridional circulation cells more than GM mutual friction. The boundary condition on the superfluid component, whether no slip or perfect slip, does not affect the large-scale structure of the flow appreciably, but it does alter the cores of the circulation cells, especially at lower Re. As Re increases, and after initial transients die away, the mutual friction force dominates the vortex tension, and the streamlines of the superfluid and normal fluid components increasingly resemble each other. In non-axisymmetric superfluid SCF, three-dimensional vortex structures are classified according to topological invariants. For misaligned spheres, the flow is focal throughout most of its volume, except for thread-like zones where it is strain-dominated near the equator (inviscid component) and poles (viscous component). A wedge-shaped isosurface of vorticity rotates around the equator at roughly the rotation period. For a freely precessing outer sphere, the flow is equally strain-and vorticity-dominated throughout its volume. Unstable focus/contracting points are slightly more common than stable node/saddle/saddle points in the viscous component, but not in the inviscid component. Isosurfaces of positive and negative vorticity form interlocking poloidal ribbons (viscous component) or toroidal tongues (inviscid component) which attach and detach at roughly the rotation period. 222

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“…Ces « défauts » sont de deux types. Le long des parois paralleles a 0, il apparait une zone dite irrotationnelle, equivalente, dans le modele continu, a une zone sans vortex (n = 0) d'épaisseur do ~ 0,29 il-1/2 mm [9]; ce manque de vor- Fig. 1.…”

Section: Classificationunclassified