Vortex line density in counterflowing He II with laminar and turbulent normal fluid velocity profiles

Baggaley, A.W. and Laizet, S. (2013) Vortex line density in counterflowing He II with laminar and turbulent normal fluid velocity profiles. Physics of Fluids, 25(115101), (doi: 10.1063/1.4828892)

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Abstract

Superfluid helium is an intimate mixture of a viscous normal fluid, with continuous vorticity, and an inviscid superfluid, where vorticity is constrained to thin, stable topological defects. One mechanism to generate turbulence in this system is through the application of a heat flux, so-called thermal counterflow. Of particular interest is how turbulence in the superfluid responds to both a laminar and turbulent normal fluid in the presence of walls. We model superfluid vortex lines as reconnecting space curves with fixed circulation, and consider both laminar (Poiseuille) and turbulent normal fluid flows in a channel configuration. Using high resolution numerical simulations we show that turbulence in the normal fluid sustains a notably higher vortex line density than a laminar flow with the same mean flow rate. We examine Vinen's relation, L−−√=γvns , between the steady state vortex line density L and the counterflow velocity v ns . Our results support the hypothesis that transition to turbulence in the normal fluid is responsible for the TI to TII transition. We also consider the spectral properties of fluctuations of the superfluid vortices, which show a good agreement with previous experimental results.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Baggaley, Dr Andrew
Authors: Baggaley, A.W., and Laizet, S.
College/School:College of Science and Engineering > School of Mathematics and Statistics > Mathematics
Journal Name:Physics of Fluids
Publisher:American Institute of Physics
ISSN:1070-6631

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