Numerical simulations of air entrainment in a plunging jet of liquid

• A translating impacting jet is numerically studied.
• Several series of numerical experiments were performed by varying the parameters (velocity, angle and thickness).
• The unsteady dynamics of the air cavities generation was observed from the impact of the jet to the deterioration of the air pockets.
• An original VOF-SM method is used: the method is capable to deal with strong interface distortions in an agitated flow.

Air entrainment upon impact of a jet of liquid is a phenomenon present in wide variety of applications. We performed a series of two-dimensional simulations consisting in three different conditions of jet impingement and compared the results to experimental data. This study was first dedicated to the establishment of the numerical configuration and the setting of the injection parameters of the jet. We studied the dynamics of air entrainment by the jets impacting on the surface of the water in a tank, from the creation of the aerated cavities to the motion of the bubble plumes resulting from their deterioration of the cavities. The results concerned time-dependent and transient phenomena. To validate the simulations, we made several comparisons with experimental data, considering three angles of jet impact. Finally, we compared two numerical models for the free-surface description, using the most prevalent method in the literature and an original free-surface tracking method recently developed in our numerical tool. We showed that the formation of air cavities was similar for each condition and each numerical model, in agreement with the experimental results. Moreover, it was observed that the air entrainment had a different behavior depending on the conditions of jet impact.