Numerical estimation of air core length in two-phase free surface vortex

Abstract

The free-surface vortex is simulated with the homogeneous mixture approach. In order to define suitable boundary conditions in the two-phase flow field, a numerical strategy is proposed on the air mass conservation in a recirculating flow system. The numerical approach is verified from an experiment. Numerical results agreed well with the experiment not only in the vortex circulation but also in the axial velocity gradient. On the homogeneous mixture assumption, the compressibility corrections for the turbulence modelling had almost no effect on the result in this case study. In order to estimate the continuous air–core length, the visible air–core interface was assumed to be characterized by the constant void fraction. With validated numerical results, vortex air core was visualized by the air volume fraction, based on the air–core length in not only the experiment but also the analytical model in the applicable range.