CFD approaches for modeling bubble entrainment by an impinging jet

This contribution presents different approaches for the modeling of air entrainment under water by a plunging jet. Since the generation of bubbles happens on a scale which is smaller than the bubbles, this process cannot be resolved in meso-scale simulations, which include the full length of the jet and its environment. This is why the air entrainment has to be modeled in meso-scale simulations.
In the frame of an Euler-Euler simulation, the local morphology of the phases has to be considered in the drag model. For example the air is a continuous phase above the water level but bubbly below the water level. Various drag models are tested and their influence on the gas void fraction below the water level is discussed.
As a first approach the air is modelled as dispersed phase everywhere in the domain. This causes an air entrainment which is obviously determined by numerical effects. Thus, this approach is not suitable for the implementation of a physical model for gas entrainment. The algebraic interface area density (AIAD) model applies a drag coefficient for bubbles and a different drag coefficient for the free surface. If the AIAD model is used for the simulation of impinging jets, the gas entrainment depends on the free parameters included in this model. The calculated gas entrainment can be adapted via these parameters. Therefore, an advanced AIAD approach could be used in future for the implementation of models (e.g. correlations) for the gas entrainment.