Hamiltonian Principle in Binary Mixtures of Euler Fluids with   Applications to the Second Sound Phenomena
  In the present paper we compare the theory of mixtures based on Rational Thermomechanics with the one obtained by Hamilton principle. We prove that the two theories coincide in the adiabatic case when the action is constructed with the intrinsic Lagrangian. In the complete thermodynamical case we show that we have also coincidence in the case of low temperature when the second sound phenomena arises for superfluid Helium and crystals. 
Henri Gouin (LMMT, M2P2), Tommaso Ruggeri