Special Session 2: New frontiers in the compressible mathematical fluid mechanics and thermodynamics

Relative entropy method and applications for the compressible two-fluid flows
Ewelina Zatorska
University of Warwick
England
Co-Author(s):    Yang Li, Maria Lukacova-Medvidova, Milan Pokorny
Abstract:
I will present a model of compressible two viscous fluids flow with a common velocity field and algebraic closure for the pressure law. The constitutive relation involves densities of both fluids through an implicit function. The existence of global-in-time finite energy weak solutions to this system is known since the work of Novotn\`{y} and Pokorn\`{y} [Arch. Rational Mech. Anal., 2020]. On the other hand, existence of local-in-time strong solutions is due to Piasecki and Zatorska [J. Math Fluid Mech., 2022]. In this talk I will focus on the weak--strong uniqueness principle using the relative entropy method. In sharp contrast to the two-phase model of Baer-Nunziato type, the volume fraction of one of phases obeys a transport equation with an additional nonlinear term. This gives rise to troublesome terms in the relative entropy inequality. We are able to close the estimate by making an elaborate use of the structure of the system.