Quantum turbulence in Helium II (at very low temperature) Lattice-Boltzmann numerical simulations of the two-fluid model Influence of boundary conditions on the stability of superfluid counter-flows

Helium-II at (finite) temperature below the transition T ≈ 2.17 K can be described as the superposition of two interacting fluids. A normal fluid which has non-zero viscosity and an inviscid superfluid, in which vorticity is confined to quantized vortices [1]. The large-scale dynamics of these two copenetrating fluids obey respectively the Navier-Stokes and Euler equations (at low Mach number) coupled together by a mutual friction force that encompasses interactions between the quantized vortices and thermal excitations of the normal fluid. This is the general framework of the so-called two-fluid model initiated by Landau and Tisza [2].