Quasiclassical and ultraquantum decay of superfluid turbulence

TL;DR

This paper develops a model that explains the hydrodynamical nature of ultraquantum and quasiclassical decay regimes in superfluid turbulence, clarifying their generation mechanisms and the role of anisotropy.

Contribution

It introduces a unified model that reproduces both decay regimes and elucidates their hydrodynamical differences and generation mechanisms.

Findings

The model reproduces both ultraquantum and quasiclassical decay regimes.

Anisotropy of vortex beam influences large-scale motion in turbulence.

Generation mechanisms depend on the forcing scale and beam anisotropy.

Abstract

This letter addresses the question which, after a decade-long discussion, still remains open: what is the nature of the ultraquantum regime of decay of quantum turbulence? The model developed in this work reproduces both the ultraquantum and the quasiclassical decay regimes and explains their hydrodynamical natures. In the case where turbulence is generated by forcing at some intermediate lengthscale, e.g. by the beam of vortex rings in the experiment of Walmsley and Golov [Phys. Rev. Lett. {\bf 100}, 245301 (2008)], we explained the mechanisms of generation of both ultraquantum and quasiclassical regimes. We also found that the anisotropy of the beam is important for generating the large scale motion associated with the quasiclassical regime.