Particles-vortex interactions and flow visualization in He4

TL;DR

This paper reviews recent advances in understanding how tracer particles interact with quantized vortices in superfluid helium-4, crucial for interpreting flow visualization experiments like PIV.

Contribution

It synthesizes recent theoretical, numerical, and experimental findings, clarifying particle-vortex interactions and addressing previous inconsistencies in superfluid turbulence studies.

Findings

Particles can become trapped on vortex cores.

Interactions significantly influence particle motion in superfluid helium.

Detection of vortices via negative ion bubbles is also discussed.

Abstract

Recent experiments have demonstrated a remarkable progress in implementing and use of the Particle Image Velocimetry (PIV) and particle tracking techniques for the study of turbulence in He4. However, an interpretation of the experimental data in the superfluid phase requires understanding how the motion of tracer particles is affected by the two components, the viscous normal fluid and the inviscid superfluid. Of a particular importance is the problem of particle interactions with quantized vortex lines which may not only strongly affect the particle motion, but, under certain conditions, may even trap particles on quantized vortex cores. The article reviews recent theoretical, numerical, and experimental results in this rapidly developing area of research, putting critically together recent results, and solving apparent inconsistencies. Also discussed is a closely related technique of detection of quantized vortices negative ion bubbles in He4.