Dynamics of twisted vortex bundles and laminar propagation of the vortex front

TL;DR

This paper investigates the dynamics of twisted vortex bundles in superfluid 3He-B, analyzing their laminar propagation, stability, and comparison with experimental vortex-front velocities, revealing insights into vortex behavior in superfluid turbulence.

Contribution

It introduces a theoretical framework for vortex bundle dynamics, including laminar propagation and instability analysis, and compares predictions with experimental data in superfluid 3He-B.

Findings

Vortex front can propagate with finite velocity even at zero temperature.

Linear torsion oscillation is a special case of inertial wave mode.

The theory aligns with experimental vortex-front velocities.

Abstract

The paper is studying the dynamics of twisted vortex bundles, which were detected in experimental investigations of superfluid turbulence in superfluid 3He-B. The analysis shows that a linear torsion oscillation of a vortex bundle is a particular case of the slow vortex mode related with the inertial wave, which was already investigated in the past in connection with observation of the Tkachenko waves in superfluid 4He and the experiments on the slow vortex relaxation in superfluid 3He-B. The paper addresses also a twisted vortex bundle terminating at a lateral wall of a container starting from the elementary case when the bundle reduces to a single vortex. The theory considers the laminar regime of the vortex-bundle evolution and investigates the Glaberson-Johnson-Ostermeier instability of the laminar regime, which is a precursor for the transition to the turbulent regime at strong twist of the bundle. The propagation and the rotation velocities of the vortex front (the segment of the vortex bundle diverging to the wall) can be found from the equations of balance for the linear and the angular momenta, and the energy. It is demonstrated that the vortex front can move with finite velocity even in the absence of mutual friction (the T = 0 limit). The theory is compared with experimental results on vortex-front propagation in superfluid 3He-B.