Normal component of a superfluid
= Normal component of a superfluid
{title2=$\mathbf v_n$}
= Normal fluid
{synonym}
The normal component of a <superfluid> describes the momentum and entropy carried by excitations rather than the phase-gradient condensate current. Its <velocity> need not equal the <superfluid velocity>. In phenomenological condensate equations, prescribing its motion supplies a reference flow for dissipation; a full two-component fluid theory would also evolve its momentum and energy.