Multi-Model Formulation for Compressible Multiphysics and Multiphase Flows: An Efficient Coupling Algorithm

A coupling between a general multiphase flows model and a two-phase dilute flow model is presented. Both models are based on Eulerian approach (two fluids models) and compressible flows are considered. This coupling permits to solve problems in which a multiphase description (involving N phases) is necessary to obtain a good physical behavior of the flow on short times: it corresponds to a given location on the computational domain. Then the flow is developing and far from the location of the initial establishment of the flow, a simpler model can be used, for example a dilute two-phase model one. A methodology for coupling both models is necessary in order to get efficient calculations and a physical consistency. This coupling is not only a challenge regarding the computing resources or the programming. We also require that the wave patterns are correctly transmitted through the coupling interface. We then developed specific Riemann solvers that allow the transmission of acoustic or material waves. We also require the preservation of the conservative quantities such as mass, momentum and energy. The method is checked on ID case: propagation of uniform flows, shock tubes. Multidimensional problem are also presented, showing the efficiency of the coupling methodology regarding CPU time.