Energy and angular momentum balance in wall-bounded superfluid turbulence

TL;DR

This study investigates the energy and angular momentum transfer in wall-bounded superfluid 3He-B, revealing that while energy dissipation persists due to quantum turbulence, angular momentum exchange nearly vanishes at low temperatures, indicating distinct effective friction mechanisms.

Contribution

It demonstrates that energy dissipation and angular momentum transfer in superfluid turbulence are governed by separate effective friction parameters at low temperatures.

Findings

Quantum turbulence causes energy dissipation in superfluid 3He-B.

Angular momentum exchange with the container nearly vanishes at low temperatures.

Distinct effective friction parameters are needed for energy and momentum transfer.

Abstract

A superfluid in the absence of the viscous normal component should be the best realization of an ideal inviscid Euler fluid. As expressed by d'Alembert's famous paradox, an ideal fluid does not exert drag on bodies past which it flows, or in other words, it does not exchange momentum with them. Also, the flow of an ideal fluid does not dissipate kinetic energy. We study experimentally whether these properties apply to the flow of superfluid 3He-B in a rotating cylinder at low temperatures. It is found that ideal behavior is broken by quantum turbulence, which leads to substantial energy dissipation, as observed also earlier. Here we show that remarkably, nearly ideal behavior is preserved with respect to the angular-momentum exchange between the superfluid and its container, i.e., the drag almost disappears in the zero-temperature limit. This mismatch between energy and angular-momentum transfer results in a new physical situation where the proper description of wall-bounded quantum turbulence requires two effective friction parameters, one for energy dissipation and another for momentum coupling, which become substantially different at very low temperatures.