  In Fermi superfluids, like superfluid 3He, the viscous normal component can
be considered to be stationary with respect to the container. The normal
component interacts with the superfluid component via mutual friction which
damps the motion of quantized vortex lines and eventually couples the
superfluid component to the container. With decreasing temperature and mutual
friction the internal dynamics of the superfluid component becomes more
important compared to the damping and coupling effects from the normal
component. This causes profound changes in superfluid dynamics: the
temperature-dependent transition from laminar to turbulent vortex motion and
the decoupling from the reference frame of the container at even lower
temperatures.
