The superfluid Reynolds number and the transition from potential flow to turbulence in superfluid $^4$He at mK temperatures

TL;DR

This paper discusses a new superfluid Reynolds number that helps analyze the transition from potential flow to turbulence in superfluid helium at millikelvin temperatures, highlighting its relevance to turbulence lifetime.

Contribution

It introduces a superfluid Reynolds number and demonstrates its usefulness in analyzing turbulence transition and lifetime in superfluid helium.

Findings

Rapid increase in turbulence lifetime with superfluid Reynolds number

Comparison of supertransient turbulence with classical pipe flow

Validation of the superfluid Reynolds number in experimental data

Abstract

This comment is on Phys.Rev.Lett. 144, 155302 (2015) by M.T. Reeves, T.P. Billam, B.P. Anderson, and A.S. Bradley "Identifying a superfluid Reynolds number via dynamical similarity" where a new superfluid Reynolds number is introduced. This definition is shown to be useful in the data analysis of the finite lifetime of turbulence observed with an oscillating sphere in superfluid helium at mK temperatures in a small velocity interval $\Delta v =(v-v_c)$ just above the critical velocity $v_c$. The very rapid increase of the lifetime with increasing superfluid Reynolds number is compared with the "supertransient" turbulence observed in classical pipe flow.