Interface Resolved Simulation of Two-Phase Flow within a Steam Separator Geometry

Abstract

Steam separators have been an integral component in the current operating Boiling Water Reactor (BWR) fleet and will continue to play a role in new BWR reactor designs. Mechanistic models used in the design process may utilize the insights gained from high resolution experiments which can increase safety/operational margins. However, direct observation of the complex two-phase flow within steam separators at operational conditions is both difficult and expensive to achieve. An alternative approach to real-world experimentation exists in the form of numerical experiments using Direct Numerical Simulation (DNS). In this work, a model of a steam separator is simulated using the PHASTA two-phase incompressible finite element code. PHASTA can directly resolve the motion of droplets/bubbles using an interface capturing approach via the Level Set method. Specifically, the effect of the pickoff-ring is examined through metrics like the outlet flow quality and steam carryunder. Time-averaged statistics are also acquired for future use in system model improvements. By using massively parallel HPC systems, high Reynolds number flows can be fully resolved, although it is still well below prototypical BWR conditions.