A Kelvin-wave cascade on a vortex in superfluid $^4$He at a very low temperature

TL;DR

This paper uses computer simulations to demonstrate that Kelvin waves on a vortex in superfluid helium-4 develop a cascade spectrum at very low temperatures, driven by non-linear interactions and phonon radiation.

Contribution

It reveals a universal Kelvin-wave cascade spectrum resulting from non-linear coupling, independent of excitation parameters, relevant to superfluid turbulence decay.

Findings

Kelvin waves exhibit a cascade spectrum insensitive to drive strength.

Energy flows to higher wavenumbers through non-linear interactions.

Kelvin-wave cascade is driven by phonon radiation at high frequencies.

Abstract

A study by computer simulation is reported of the behaviour of a quantized vortex line at a very low temperature when there is continuous excitation of low-frequency Kelvin waves. There is no dissipation except by phonon radiation at a very high frequency. It is shown that non-linear coupling leads to a net flow of energy to higher wavenumbers and to the development of a simple spectrum of Kelvin waves that is insensitive to the strength and frequency of the exciting drive. The results are likely to be relevant to the decay of turbulence in superfluid $^4$He at very low temperatures.