Three dimensional evaluation of two-phase flow in BWR fuel bundles based on compressible two fluid-one pressure and κ-ε turbulence models

The three dimensional fluid dynamic code system was developed to simulate a comprehensive two-phase flow field in fuel bundles of boiling water reactors. The system is based on the compressible two fluid-one pressure (six equations) model and is designed to be applicable to both detailed fully three dimensional geometries and porous medium sub-channel type geometries. In the detailed modeling, the turbulence effect is considered by the additional four conservation equations of the κ-ε turbulence model and the convective terms are formulated by the modified skewed upwind scheme. The sub-channel type modeling, in contrast, is built from coarser meshes. The empirical void drift and turbulence mixing models are introduced to replace the κ-ε turbulence model and other additional constitutive models such as the local loss are added to facilitate efficient sub-channel-type calculations. General problems were investigated regarding numerical methodologies in discretizing a vapor-liquid two-phase flow field based on the two fluid-one pressure model. The performances of several pressure iteration schemes were compared in combination with the outer Newton-Raphson iteration loop. (Author)