Bubble flows from underwater orifices are fundamental to gas–liquid operations, although the influence of orifice geometry on bubble dynamics and induced flows remains underexplored. Shadowgraphy and laser-induced fluorescence particle image velocimetry are employed to investigate bubbles released into a quiescent liquid from circular and elliptical orifices with aspect ratios AR = 1–4. Elliptical orifices produce smaller bubbles with higher aspect ratios and greater morphological complexity. These features result from anisotropic contact angles along the orifice edge, which induce non-uniform capillary forces and strong deformation at detachment. This mechanism drives high-amplitude zigzag trajectories, distinct from the spiral paths observed with circular orifices. A force-budget analysis attributes the enhanced lateral drift to rotation-induced forces. In the wake, circular orifices sustain coherent counter-rotating vortices, whereas elliptical orifices promote irregular shedding and multiscale structures. The induced turbulence spectra follow an approximate -2 scaling. Furthermore, flows from elliptical orifices exhibit a higher fractal dimension of the turbulent/non-turbulent interface and stronger entrainment, with a marked increase in the engulfment flux. These results quantify the mechanisms by which orifice geometry determines bubble dynamics and the developing flow field.
Wang et al. (2026) studied this question.