Abstract
Free surface disruption, bubble entrainment, and resulting bubbly wake due to a stationary and moving horizontal jets plunging into a quiescent liquid were studied both numerically and experimentally. The moving jet wake showed significantly different flow characteristics than the stationary jet wake. High speed videos revealed that large vortical structures with entrapped air were generated periodically from the horizontal plunging jet. Each vortical air pocket broke up into multiple bubbles due to local shear flows as it returned toward the free surface and moved downstream. The frequency of the air pocket occurrence was analyzed and found to scale with the plunging jet flow and geometry conditions. The plunging dynamics was simulated with an Eulerian/Lagrangian one-way coupled two-phase flow model, which included a Level-Set method and a sub-grid bubble entrainment model. These captured free surface dynamics and predicted the bubble generation and entrainment. The flow structures, velocity field, and overall bubble spreading region near the plunging region were well captured by the numerical model. Further improvement on downstream wake flow is being sought through two-way coupling between the two phases since the one-way coupling does not account properly for the effective density.