Numerical simulation of bubbly jets in crossflow using OpenFOAM

Abstract

This paper conducted a computational fluid dynamics study of bubbly jets (not bubble plumes due to pure gas injection) in crossflow to explore the hydrodynamics that are still unknown. A three-dimensional model was developed, calibrated, and validated by coupling the Euler–Euler two-fluid model with unsteady Reynolds-averaged Navier–Stokes approach in OpenFOAM. The results showed that the modeled gas void fraction, bubble velocity, water jet centerline trajectory, and jet expansion agree well with the experimental data. The vertical distribution of turbulent kinetic energy evolves from mono-peak to dual-peaks as the jet penetrates farther for the bubbly jet due to the interactions between bubbles and ambient water flow. Water velocity distribution was examined at cross sections of both the air- and water-phases of bubbly jets in crossflow, and counter-rotating vortex pairs can be clearly observed for both phases. Generally, the center-plane maximum concentration decreases in the crossflow direction. Compared to pure water jets, bubbly jets are stretched wider in the vertical direction due to the lift of bubbles, and thus, dilution is larger. Interestingly, the vorticity at water jet cross sections of bubbly jets evolves from two vertical “kidney-shapes” to two axisymmetric “thumb-up-shapes.” Moreover, effects of ambient crossflow on bubbly jet behaviors were systematically examined. As the crossflow velocity increases, the locations of maximum concentration, maximum velocity magnitude, maximum vorticity magnitude, as well as water jet centerline, all tend to be lower for bubbly jets.