From Experimental Characterization to Numerical Reconstruction: Modeling Bubble Spiral Trajectory Dynamics via UDFs-Enhanced Lagrangian Methods

There are four types of bubble ascent paths: rectilinear, zigzag, spiral, and chaotic, but fewer quantitative studies on the dynamics of bubble spiral motion. In this paper, the spiral path dynamics of a single bubble with an initial diameter of 1.75–3.86 mm in still water is investigated. The bubble position on the spiral trajectory was quantitatively characterized as a function of time using the three-dimensional shadow imaging technique combined with image digitization processing. The additional forces that induce spiral motion were derived using Newton’s second law and subsequently integrated into the Lagrangian framework through Fluent User-Defined Functions (UDFs) to reproduce the spiral trajectory of the single bubble. The simulation results for bubble velocity and trajectory closely matched the experimental data. The forces, accelerations, velocities, trajectories, and swept volumes of the bubbles are discussed. Compared to the rectilinear motion, the swept volumes of the bubbles obtained after considering the spiral paths were increased by 29.5%, 34.4%, 38.2%, 40.6%, and 37.1% for 1.75, 1.83, 1.93, 2.05, and 3.86 mm, respectively. These results will contribute to a better understanding of the dynamic behavior of the bubble spiral motion.