Counterflow quantum turbulence in a square channel under the normal fluid with a Poiseuille flow

TL;DR

This study uses numerical simulations to analyze vortex tangles in superfluid helium under counterflow conditions in a square channel with a laminar normal fluid, revealing inhomogeneous vortex distributions influenced by temperature and flow profiles.

Contribution

It provides new insights into the vortex tangle structure in the TI state with solid boundaries and laminar normal fluid flow, using the vortex filament model.

Findings

Vortex tangle concentrates near solid boundaries.

Inhomogeneity depends on temperature due to competing effects.

Vortex tangle exhibits characteristic space-time oscillations.

Abstract

We perform a numerical analysis of superfluid turbulence produced by thermal counterflow in He II by using the vortex filament model. Counterflow in a low aspect ratio channel is known to show the transition from laminar flow to the two turbulent states TI and TII. The present understanding is that the TI has the turbulent superfluid and the laminar normal fluid but both fluids are turbulent in the TII state. This work studies the vortex tangle in the TI state. Solid boundary condition is applied to walls of a square channel, and the velocity field of the normal fluid is prescribed to be a laminar Poiseuille profile. An inhomogeneous vortex tangle, which concentrates near the solid boundaries, is obtained as the statistically steady state. It is sustained by its characteristic space-time oscillation. The inhomogeneity of the vortex tangle shows the characteristic dependence on temperature, which is caused by two competitive effects, namely the profile of the counterflow velocity and the mutual friction.