Transition to superfluid turbulence governed by an intrinsic parameter

TL;DR

This paper reports a temperature-driven transition in superfluid 3He-B from regular to turbulent flow, governed by an intrinsic parameter related to vortex damping, providing new insights into superfluid turbulence.

Contribution

It identifies a sharp, velocity-independent transition at 0.60Tc in superfluid 3He-B, governed by vortex damping, resolving previous experimental conflicts and revealing an intrinsic turbulence criterion.

Findings

Transition at 0.60Tc between regular and turbulent regimes

Transition is insensitive to flow velocity

Damped vortex behavior determines turbulence onset

Abstract

Hydrodynamic flow in both classical and quantum fluids can be either laminar or turbulent. To describe the latter, vortices in turbulent flow are modelled with stable vortex filaments. While this is an idealization in classical fluids, vortices are real topologically stable quantized objects in superfluids. Thus superfluid turbulence is thought to hold the key to new understanding on turbulence in general. The fermion superfluid 3He offers further possibilities owing to a large variation in its hydrodynamic characteristics over the experimentally accessible temperatures. While studying the hydrodynamics of the B phase of superfluid 3He, we discovered a sharp transition at 0.60Tc between two regimes, with regular behaviour at high-temperatures and turbulence at low-temperatures. Unlike in classical fluids, this transition is insensitive to velocity and occurs at a temperature where the dissipative vortex damping drops below a critical limit. This discovery resolves the conflict between existing high- and low-temperature measurements in 3He-B: At high temperatures in rotating flow a vortex loop injected into superflow has been observed to expand monotonically to a single rectilinear vortex line, while at very low temperatures a tangled network of quantized vortex lines can be generated in a quiescent bath with a vibrating wire. The solution of this conflict reveals a new intrinsic criterion for the existence of superfluid turbulence.