Simulations of Vortex Evolution and Phase Slip in Oscillatory Potential Flow of the Superfluid Component of Helium-4 Through an Aperture

TL;DR

This paper simulates vortex loop evolution in oscillating superfluid helium flow, revealing how increasing frequency affects vortex escape and energy transfer, with vortex loops being drawn back into the aperture at high frequencies.

Contribution

It introduces simulations of vortex dynamics in oscillatory superfluid flow, highlighting the frequency-dependent behavior of vortex escape and phase-slip events.

Findings

Vortex loops are drawn back toward the aperture at higher frequencies.

Escape size of vortex loops decreases with increasing oscillation frequency.

Above a certain threshold frequency, vortex loops re-enter the aperture.

Abstract

The evolution of semicircular quantum vortex loops in oscillating potential flow emerging from an aperture is simulated in some highly symmetrical cases. As the frequency of potential flow oscillation increases, vortex loops that are evolving so as eventually to cross all of the streamlines of potential flow are drawn back toward the aperture when the flow reverses. As a result, the escape size of the vortex loops, and hence the net energy transferred from potential flow to vortex flow in such 2 Pi phase-slip events, decreases as the oscillation frequency increases. Above some aperture-dependent and flow-dependent threshold frequency, vortex loops are drawn back into the aperture. Simulations are preformed using both radial potential flow and oblate-spheroidal potential flow.