Application of hot-wire anemometry to He II superfluid turbulence EuHIT Funded Project

### Team

Pantxo Diribarne
Sbt, Grenoble, France

### Overview

Research Infrastructure
CEA Grenoble Helium Infrastructures, France
Facilities used
HeJet (HeJet)
In the quest for probing a small-scale behavior of superfluid turbulent flows, a new candidate probe has been recently proposed, namely the hot-wire. Such probes are customary for the study of classical turbulence but only recently researchers have discovered the possibility to make use of them in the context of superfluid turbulence. The enhancement of heat transfer due to forced convection is the basic principle of hot-wire velocity probes, and such enhacement is also measurable in superfluid flows at temperatures between 1.6 K and the superfluid transition temperature, $$T_{\lambda }\approx 2.17{K}$$. Unfortunately up to now no satisfactory mechanism has been proposed to explain why/how these probes work in superfluids. Indeed, heat transport in superfluid helium is very peculiar (the most efficient mechanism is not diffusive but convective, that is the thermal counterflow which does not have an analogue in classical fluids), and the concept of thermal boundary layer, which explains the heat transfer enhancement in classical fluids, for superfluids is not well defined. In this project we propose to advance an experimental study, combined with simple theoretical modelling, aiming at better understanding of the heat transfer between the hot-wire probe and turbulent superfluid helium. Such a study will ultimately result in solving the problem of the hot-wire calibration with temperature and fluid velocity in the wide range of these quantities. If sufficiently developed, the hot-wire technique may, in particular, become a valuable tool for the investigation of turbulent properties of the normal component in turbulent superfluid $$^{4}$$He. Furthermore, this technique will greatly assist experimental studies of regimes, structures, spectra and decay of superfluid turbulence.