Frequency Dependence of the Critical Velocity of a Sphere Oscillating in Superfluid Helium-4

TL;DR

The paper demonstrates that the critical velocity of a sphere oscillating in superfluid helium-4 depends on the square root of the oscillation frequency, largely unaffected by sphere size or temperature.

Contribution

It introduces a simple dimensional argument explaining the frequency dependence of critical velocity in superfluid helium-4 oscillations.

Findings

Critical velocity increases with the square root of frequency

Sphere size and temperature have minimal effect

Surface properties and vorticity may influence but are not systematically studied

Abstract

It is shown that the critical velocity of a small sphere oscillating in superfluid helium increases with the square root of the oscillation frequency. This behavior can be described by a simple dimensional argument. The size of the sphere and the temperature of the superfluid are found to have no or only very little effect. Surface properties of the sphere and remanent vorticity may have an influence but have not been under systematic investigation in these measurements