Flow of He II due to an Oscillating Grid in the Low Temperature Limit

TL;DR

This paper investigates the behavior of superfluid helium (He II) at near-zero temperatures using an oscillating grid, revealing nonlinear flow responses, vortex boundary layer growth, and a transition to turbulence.

Contribution

It introduces experimental observations of flow transitions and vortex boundary layer development in He II at very low temperatures using an oscillating grid.

Findings

Resonant frequency decreases with increasing oscillation amplitude.

Flow becomes strongly nonlinear due to vortex boundary layer growth.

Flow transitions to turbulence at high oscillation amplitudes.

Abstract

The macroscopic flow properties of pure He II are probed in the limit of zero temperature using an oscillating grid. With increasing oscillation amplitude the initially pure superflow changes abruptly: the resonant frequency decreases and the response becomes strongly nonlinear, attributable to the growth of a boundary layer of quantized vortices that increases the effective mass of the grid. On further increase of oscillation amplitude, the flow undergoes a transition to turbulence.