Numerical simulation of bubble hydrodynamics for pool scrubbing

Pool scrubbing is an important filtering process that prevents radioactive aerosols from entering the environment in the event of severe accidents in a nuclear reactor. In the process of transporting aerosol particles using bubbles, bubble hydrodynamics plays a crucial role in modeling pool scrubbing and significantly affects particle removal in a bubble. Our future research strategy is to apply the three-dimensional Computational Fluid Dynamics (CFD) approach to understand the detailed bubble interaction, which is difficult to be assessed experimentally. This study validates the applicability of the CFD simulation to bubble hydrodynamics at the flow transition from a globule to a swarm region. Two types of solvers based on the Volume Of Fluid (VOF) and Simple Coupled Volume Of Fluid with Level Set (S-CLSVOF) methods were used to capture the gas-liquid interface in the CFD simulation. We use the experimental data for validation. As a result, the VOF and S-CLSVOF methods accurately predict the bubble size and void fraction distributions. In addition, we confirmed that the bubble rise velocity of the S-CLSVOF method almost agrees with the experimental results. The validated code is expected to play a critical role in evaluating the constitutive equations in the stand-alone pool scrubbing code - SPARC-90.