(70a) CFD Simulation of Various Flow Regimes in Two-Phase Gas-Liquid Flows

Many industrial flow applications involve two-phase gas-liquid flows in complex geometry. Computational fluid dynamics (CFD) simulations of two-phase flow systems by resolving the flow at the gas-liquid interface can successfully handle problems, where the interface length scales can be resolved by the computational grid. The Eulerian slip-formulation, which allows each phase to be represented by its own phase field (momentum, energy, etc.), can be used for accurate predictions where one of the phases is distributed as small size droplets or bubbles. This is an advantage when the length scale of the droplets/ bubbles is smaller than the length scales that can be represented on the mesh. This paper presents an application of a modified Eulerian slip-formulation method which adapts the inter-phase exchange (such as momentum exchange) to the local flow conditions. This method handles the large scale separate regions of gas and liquid using the Large Scale Interface (LSI) modeling approach. The interphase exchange modeling in dispersed flow regions is sensitized to the local flow characteristics and mesh resolution, by specifying a user defined interface length scale that is used in calculating the interphase exchange terms. The application presented in this paper is a complex piping system with multiple out-of-plane bends connecting horizontal and vertical sections with changes in cross-sectional area. In the application presented, some flow regions may see large resolvable gas or liquid pockets, and in other regions the gas or liquid is present in bubble or droplet form that cannot be resolved by the mesh. The various flow regimes simulated are stratified-wavy, annular, misty, and churn flow regimes for two-phase, immiscible gas-liquid flow in horizontal and vertical pipes with adiabatic walls.