Large-scale superfluid vortex rings at nonzero temperatures
  We numerically model experiments in which large-scale vortex rings - bundles of quantized vortex loops - are created in superfluid helium by a piston-cylinder arrangement. We show that the presence of a normal fluid vortex ring together with the quantized vortices is essential to explain the coherence of these large-scale vortex structures at nonzero temperatures, as observed experimentally. Finally we argue that the interaction of superfluid and normal fluid vortex bundles is relevant to recent investigations of superfluid turbulence. 
Daniel H. Wacks, Andrew W. Baggaley, Carlo F. Barenghi
physics.flu-dyn cond-mat.other