Decay of Counterflow Quantum Turbulence in Superfluid ^4He

TL;DR

This paper simulates the decay of quantum turbulence in superfluid helium-4, confirming the Vinen equation's predictions and exploring parameters linking vortex line curvature and separation.

Contribution

It provides numerical validation of the Vinen equation during turbulence decay and relates key parameters governing vortex dynamics.

Findings

VLD decays as t^{-1} during decay.

Parameter c_2 relates vortex curvature to separation.

Formula connecting  and c_2 agrees with simulations.

Abstract

We have simulated the decay of thermal counterflow quantum turbulence from a statistically steady state at T=1.9[K], with the assumption that the normal fluid is at rest during the decay. The results are consistent with the predictions of the Vinen equation (in essence the vortex line density (VLD) decays as t^{-1}). For the statistically steady state, we determine the parameter c_2, which connects the curvature of the vortex lines and the mean separation of vortices. A formula connecting the parameter \chi_2 of the Vinen equation with c_2 is shown to agree with the results of the simulations. Disagreement with experiment is discussed.