Air entrainment induced by the impact of a planar translating jet on a flat free surface

The free surface flow generated by the impact of a two-dimensional jet onto a still water surface is numerically and experimentally investigated. The plunging jet is assumed to be inclined and translating with respect to the still water. The study is aimed at exploring the mechanisms leading to the air entrainment processes taking place during the jet entry. Different flow conditions are investigated by varying the inclination angle and the translating velocity of the impacting jet, although only a single condition is presented in the current work. Experimentally, the free surface dynamics are observed with a high-speed digital camera. The same problem is numerically simulated using a two-fluid approach that allows for the continuous description of both phases, while accounting for the change in interface topology resulting from the air entrainment process. Both experimental and numerical results are presented, and comparisons among the two are established for a case with zero translation velocity. Although the numerical tool still requires further improvements, the comparison with experimental data in terms of free surface dynamics and the time and depth for pinch-off of the entrained air bubble are in general qualitative and quantitative agreement, presenting encouraging results for further development.