Numerical simulations of bubbly flows in a vertical periodic channel

Abstract

In this study, numerical simulations of bubbly flows in an infinitely long vertical channel were performed. Generally, the upper and lower boundaries of such channels are simplified as periodic boundary conditions. Unlike horizontal channel flows, the presence of gravity in the streamwise direction complicates the establishment of periodic boundary conditions. Therefore, a specialized treatment is required to prevent fluid acceleration. Here, we developed a novel treatment for the imposition of periodic boundaries and proposed a new microbubble model to consider the surface tension effect of microbubbles. To detect each bubble in the flow field, we implemented a bubble identification algorithm, which facilitates a thorough statistical analysis of bubble number, size, and spatial distribution. Validation tests were conducted, and good agreement was achieved between our results and reference data. We also confirmed that the results obtained with periodic boundaries are consistent with those achieved without them. Finally, we simulated the evolution of rising bubble swarms in a quiescent liquid. The method presented here contributes to the numerical simulations of bubbly flows in industrial systems, including oil-gas transportation, bubble columns, and nuclear reactors.