Large-scale superfluid vortex rings at nonzero temperatures

Abstract

We numerically model experiments in which large-scale vortex rings - bundles of quantized vortex loops - are created in superfluid helium by a piston-cylinder arrangement. We show that the presence of a normal fluid vortex ring together with the quantized vortices is essential to explain the coherence of these large-scale vortex structures at nonzero temperatures, as observed experimentally. Finally we argue that the interaction of superfluid and normal fluid vortex bundles is relevant to recent investigations of superfluid turbulence.Comment: 8 pages, 5 figure

Hamiltonian bifurcation perspective on two interacting vortex pairs: From symmetric to asymmetric leapfrogging, period doubling, and chaos

“…This effort paves the way for numerous possible paths in the future for related systems. While the wealth of associated phenomena may grow considerably and the insight of the techniques used herein is more limited to low-dimensional settings, it would certainly be worthwhile to examine the possibility of leapfrogging phenomena/features in settings involving 6-or 8-vortices, in the spirit of the computations of [14] (and associated experiments discussed therein) for generalized leapfrogging involving more vortex pairs. For the 3-dimensional realm of vortex lines and vortex rings, studying in a systematic way the phase plane and possible motions both along the lines of [9] in the absence of a trap, as well the variant in the presence of the trap [15] will be of particular interest as a direction for future work.…”

“…These works are of considerable interest due to the intrinsically complex yet tractable nature of the vortex leapfrogging problem. In addition, recent works both at the level of analysis of experiments performed in liquid helium [14] and at that of exploring vortex rings in confined atomic Bose-Einstein condensates [8] (and also recent works such as [3,4,15]) render this phenomenology quite interesting to understand and generalize. In the context of superfluid helium experiments, there is an interest in exploring generalized leapfrogging of three, or more vortex rings [14].…”

“…In addition, recent works both at the level of analysis of experiments performed in liquid helium [14] and at that of exploring vortex rings in confined atomic Bose-Einstein condensates [8] (and also recent works such as [3,4,15]) render this phenomenology quite interesting to understand and generalize. In the context of superfluid helium experiments, there is an interest in exploring generalized leapfrogging of three, or more vortex rings [14]. On the other hand, in the BEC realm incorporating the role of the trap (which will destroy leapfrogging but will generate coherent in-trap motions of vortices and VRs [3,15]) is a subject both theoretically relevant and experimentally accessible.…”

Dynamical similarity and instabilities in high-Stokes-number oscillatory flows of superfluid helium

“…For completeness, there is a third critical velocity of hydrodynamic origin, likely associated with the development of larger vortical structures from bundles of polarized quantized vortices. We note that at finite temperature, such polarized vortex bundles or rings have been studied numerically [52,53]. The mentioned critical velocity (typically above 1 ms −1 ) might not be relevant in the two-fluid regime at all, as classical features would likely develop in the vortex tangle due to mutual friction even before this mechanism can take effect.…”

On the determination of vortex ring vorticity using Lagrangian particles

“…Such a macroscopic superfluid vortex is typically composed of a bundle of quantized vortices (see e.g. Wacks, Baggaley & Barenghi 2014) that are modelled in the HVBK framework as a continuous vorticity field. In this work we are not interested in this fast transient dynamics.…”