Modeling of the free-surface vortex-driven bubble entrainment into water

The recently developed GENTOP (Generalized Two Phase Flow) concept, which is based on the multifield Euler-Euler approach, was applied to model a free-surface vortex-a flow situation that is relevant for hydraulic intake. A new bubble entrainment model has been developed and implemented in the concept. In general, satisfactory agreement with the experimental data can be achieved. However, the gas entrainment can be significantly affected by several parameters or models used in the CFD (Computational Fluid Dynamics) simulation. The scale of curvature correction Cscale in the turbulence model, the coefficient in the entrainment model Cent, and the assigned bubble size to be entrained have a significant influence on the gas entrainment rate. The gas entrainment increases with higher Cscale values, which can be attributed to the stronger rotation captured by the simulation. A smaller bubble size gives higher gas entrainment, while a larger bubble size leads to a smaller entrainment. The results also show that the gas entrainment can be controlled by adjusting the entrainment coefficient Cent. Based on the modeling framework presented in this paper, further improvement of the physical modeling of the entrainment process should be done. © 2020 by the authors.