The superfluid Reynolds number and the transition from potential flow to turbulence in superfluid 4He at mK temperatures
Physics Department, Regensburg University, D-93040 Regensburg, Germany
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 Δ v =(v-vc) just above the critical velocity vc.
The very rapid increase of the lifetime with increasing superfluid Reynolds
number is compared with the "supertransient" turbulence observed in
classical pipe flow.