An Eulerian-Eulerian approach for Oil&Gas separator design

This paper presents a novel CFD analysis of an Oil & Gas separator, based on a multi-fluid Eulerian-Eulerian model of the Navier-Stokes equations, implemented in OpenFOAM®. The simulation of a three-phase separator poses a particular challenge to the numerical modeling of transport phenomena since the three-phase flow can span across multiple flow regimes from disperse to separate. To handle such complex behavior, a new three-phase Eulerian-Eulerian solver has been implemented in OpenFOAM with a fully implicit treatment of drag terms and with the capability to describe both disperse and separate flow at high, fully coupled phase fractions. Furthermore, the mixture turbulence model implemented in OpenFOAM for bubble flows has been improved. Firstly, the source term of the turbulent kinetic energy has been modified with a more regime-independent formulation derived from the literature. Then, the derivation of the same model has been extended in order to manage the three phases. The work represents an improvement both from an academic and industrial perspective: it provides a consistent numerical framework for a multiphase flow involving a number of phases higher than two; it replaces the traditional Eulerian-Lagrangian approach with the more appropriate Eulerian-Eulerian one for the analysis of industrial production facilities. These two aspects allow to describe more accurately the flow pattern transitions and to numerically capture the separation and phase inversion phenomena inherent to the system.