ID 189

Implementation of a Diffuse Interface Method in a Compressible Multicomponent LES Solver

 

Abstract:

This study introduces a compressible diffuse interface method to simulate multicomponent flows for regimes ranging from subcritical two-phase flows to transcritical and supercritical flows. In the prospect of simulating a full cryogenic rocket-engine ignition, the model uses a real gas cubic equation of state to take advantage of its wide domain of validity. This choice requires a careful treatment in areas where the fluid state lies into the binodal region for subcritical regimes. In this respect, the model can be related to the family of multifluid methods such as Baer and Nunziato’s 7-equation model (1986), considering velocity, pressure, temperature and chemical potential relaxations. Our objective is to restore hyperbol- icity when an unstable state is encountered. To do so, a thermodynamic equilibrium is computed under a one-fluid hypothesis based on the Corresponding States Principle, yielding a two-phase stable fluid state. This relaxation process naturally impacts the dynamics in the areas where it happens and the subse- quent consequences have been investigated. In particular, Jacobian matrices for the numerical schemes must be determined and adapted boundary conditions derivation must be provided. The method has been implemented into the unstructured solver AVBP, developed by CERFACS and IFPEN, and tested in a multidimensional flow in a subcritical regime. This allowed to observe the behavior of the model, especially in the two-phase regions.