Eulerian Multiphase (EMP)

The Eulerian Multiphase (EMP) model in Simcenter STAR-CCM+ is based on an Eulerian-Eulerian formulation where each distinct phase has its own set of conservation equations.

Phases are considered to be mixed on length scales smaller than the length scales to resolve, and coexist everywhere in the flow domain. The volume fraction is the portion of a volume that a phase occupies.

This concept of coexisting phases is called “interpenetrating continua”. The concept assumes that you are interested in the time averaged behavior of the flow, rather than the instantaneous behavior. This assumption has important implications for understanding volume fraction in the context of the Eulerian Multiphase (EMP) model.

The pressure is assumed to be the same in all phases. The volume fraction gives the share of the flow domain that each phase occupies. Each phase has its own velocity and physical properties. The term “segregated” refers to the fact that the solution algorithm uses a SIMPLE-type approach, which has separate pressure and velocity solvers.

Interfaces separate the multiple phases present in the simulation. The motions of the phases influence the interface between each pair of phases. The phases can be any kind of fluid in the sense of moving gas, liquid or solid particles. In general, the phases are not in equilibrium and each phase has its own velocity, energy, and other variables and its own physical properties.

The conservation equations for each phase variable require closure by the definition of phase interactions at each phase interface. This definition consists of suitable models for the interfacial area, and for the rates of interphase transfer of mass, momentum and energy. These closures characterize and vary between different multiphase flow patterns, and are determined from experiments or analytical solution.