Formation and decay of vorticity in coupled helium-II flow - art. no. 024513

The kinematic viscosity of helium II below the transition temperature can b e defined with the total density of the liquid or the normal-fluid density alone. These two definitions have very different temperature dependences. I n this work we considered the decay of Gaussian distributions of vorticity in helium II using the two fluid Hall-Vinen-Bekharevich-Khalatnikov equatio ns. Our calculation shows that in these two-dimensional axisymmetric flows both fluids decay together with a viscous time scale set by the total fluid density and not by the normal-fluid density alone. We also considered the spin-up of each fluid and observed that for all initial. conditions conside red both fluids tend towards a matched vorticity state.