Progress and Challenges in Multiphase CFD Method Development for Nuclear Thermal Hydraulics

Multiphase flows limit the operation of light water reactors and must thus be understood. Fundamental knowledge is often limited, and multiphase computational fluid dynamics (CFD) can contribute to this. This paper discusses progress and challenges in multiphase CFD by considering both low- and high-fidelity models, with a focus mostly on the underlying methods. At the forefront of multiphase method development for industrial applications are hybrid multiphase methods, the challenges of which are discussed extensively. High-fidelity methods, on the other hand, are more mature but require improvements for the use in problems with more complicated geometries or physics. Opportunities for improvements in both low- and high-fidelity multiphase CFD are discussed.