LandauTiszamodel
The Landau–Tisza model is a phenomenological description of superfluidity that combines key ideas from the two-fluid concept introduced by László Tisza and the excitation-focused hydrodynamic theory developed by Lev Landau. It treats a superfluid as an interpenetrating mixture of a viscous "normal" component, which carries entropy, and an inviscid "superfluid" component, which flows without dissipation. Each component has its own density and velocity fields and together satisfy conservation of mass, momentum and energy.
Historically, Tisza proposed the two-fluid picture to explain the unusual thermal and transport properties of liquid
Predictions of the model include the existence of second sound (an entropy or temperature wave), the fountain
Limitations include its phenomenological nature and limited microscopic justification in some regimes; later quantum many-body and