Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session E25: Superfluids |
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Chair: Scott Strong, Colorado School of Mines Room: 304 |
Sunday, November 22, 2015 4:50PM - 5:03PM |
E25.00001: Nonlinear Binormal Flow of Vortex Filaments Scott Strong, Lincoln Carr With the current advances in vortex imaging of Bose-Einstein condensates occurring at the Universities of Arizona, S\~ao Paulo and Cambridge, interest in vortex filament dynamics is experiencing a resurgence. Recent simulations, Salman (2013), depict dissipative mechanisms resulting from vortex ring emissions and Kelvin wave generation associated with vortex self-intersections. As the local induction approximation fails to capture reconnection events, it lacks a similar dissipative mechanism. On the other hand, Strong\&Carr (2012) showed that the exact representation of the velocity field induced by a curved segment of vortex contains higher-order corrections expressed in powers of curvature. This nonlinear binormal flow can be transformed, Hasimoto (1972), into a fully nonlinear equation of Schr\"odinger type. Continued transformation, Madelung (1926), reveals that the filament's square curvature obeys a quasilinear scalar conservation law with source term. This implies a broader range of filament dynamics than is possible with the integrable linear binormal flow. In this talk we show the affect higher-order corrections have on filament dynamics and discuss physical scales for which they may be witnessed in future experiments. [Preview Abstract] |
Sunday, November 22, 2015 5:03PM - 5:16PM |
E25.00002: Three Dimensional Vortex Reconnection Dynamics in Superfluid Helium Peter Megson, David Meichle, Daniel Lathrop Liquid helium, when cooled below 2.17 K, becomes a superfluid with exotic physical properties including flow without friction. Superfluid flow is irrotational except about line-like topological phase defects with quantized circulation, known as quantum vortices. The dynamics of these vortices include events such as reconnection and Kelvin wave propagation. We observe the dynamics of particles trapped on the vortices with a newly developed 3D stereographic system. This talk will present new observations of reconnection events and analysis comparing vortex reconnection behavior in three dimensions to previous work that observed such events in two-dimensional projection. In particular, we discuss the power law scaling of vortex separation as a function of time and the effect of the initial angle of separation between the vortex filaments. [Preview Abstract] |
Sunday, November 22, 2015 5:16PM - 5:29PM |
E25.00003: Vortex knottiness in superfluids Hridesh Kedia, Dustin Kleckner, Davide Proment, William Irvine Recent work has demonstrated that linked and knotted vortices will spontaneously unknot or untie in both classical fluids and superfluids. This effect would appear to jeopardize any notion of conservation of fluid topology (helicity), but this need not be the case: vortices can transfer their knottedness to helical coils, preserving some measure of the original topology. We ask how this notion of topology preservation behaves in the context of collections of vortices with topology. We address this question by numerical simulations of superfluid vortices in the Gross-Pitaevskii equation. [Preview Abstract] |
Sunday, November 22, 2015 5:29PM - 5:42PM |
E25.00004: Hydrodynamic Decay of Decorated Quantum Vortex Rings Luca Moriconi The decay of quantum vortex rings in HeII, visualized with the help of solid hydrogen particles trapped in their cores, has been a problematic issue within the two-fluid model of superfluidity: the large drag exerted on the vortex rings by the flow of normal fluid past the hydrogen particles would ultimately lead to decay times that mismatch the ones observed in the laboratory. We discuss a phenomenological solution of this puzzle, which is based on the fact that the vortex ring energy loss is accounted for not only by mutual friction, but also by the viscous dissipation and sweeping of the flow structures produced from the vortex ring backreaction on the normal component of the surrounding superfluid. [Preview Abstract] |
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