648	RWTH Publication No: 988937        2024
TITLE	A survey on isothermal and isentropic Baer-Nunziato-type models
AUTHORS	Maren Hantke, Siegfried Müller, Aleksey Sikstel, Ferdinand Thein
ABSTRACT	Multi-component Baer-Nunziato-type models for isothermal and isentropic fluids are investigated. These are given by balance equations for volume fractions, density and momentum for each component accounting for the relaxation to equilibrium by means of relaxation terms. Mathematical properties of the models are derived such as hyperbolicity and symmetrization. The fields are characterized and corresponding Riemann invariants are determined. Appropriate entropy-entropy flux pairs are derived taking into account the phasic energy equations including the heat flux. Physically meaningful constraints are presented that ensure the entropy inequality to hold. Instantaneous relaxation to equilibrium is investigated and appropriate algorithms are presented. Numerical results for the isothermal Baer-Nunziato model are compared to an isothermal Euler model and to an isothermal phase-field model.
KEYWORDS	Baer-Nunziato model, isentropic flow, isothermal flow, multiphase flow