Large Eddy Simulations of Turbulent Gas-Liquid Flows in a Diverging Horizontal Channel Using a Hybrid Multiphase Approach

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Centrifugal pumps conveying gas–liquid flows are often designed based on pure liquid flows due to limited understanding of gas formations within a gas–liquid flow. Computational fluid dynamics (CFD) can provide insights into the flow characteristics, yet standard multiphase models are not able to describe a wide range of spatial scales. In this study, a hybrid multiphase approach for turbulent flows based on an Eulerian-Eulerian solver with volume-of-fluid (VOF) enhancements is applied, which can handle multiple flow regimes (continuous gas/liquid, disperse bubbles) at once. Large eddy simulations (LES) of gas–liquid-flows through a diverging horizontal channel (diffuser) are performed to evaluate the possibilities and limitations of this approach. Three representative cases, each containing different flow characteristics, are computed using a fixed bubble size approach. The results show that the hybrid approach is able to capture all flow characteristics and predict the gas void size and position precisely. However, it can be observed that the performance of the approach significantly depends on the specified bubble size.