Two-fluid model is a macroscopic traffic flow model to represent traffic in a town/city or metropolitan area, put forward in the 1970s by Ilya Prigogine and Robert Herman.
[1] There is also a two-fluid model which helps explain the behavior of superfluid helium.
[2][3] This model states that there will be two components in liquid helium below its lambda point (the temperature where superfluid forms).
The ratio of superfluid density to the total density increases as the temperature approaches absolute zero.
It is possible to solve a one-dimensional coupled Euler and Navier-Stokes equations with the self-similar Ansatz as a simple model of coupled inviscid and viscous fluid system.