Simulation \& modeling of bubbles in vortex--dominated flows

Bubbles in vortex--dominated flows occur widely; e.g. turbulent shear layers, free jets, and tip vortex cavitation in propellers. Two problems are considered here: (i) bubbles entrained into the core of a line vortex and (ii) bubbles entrained into the core of a ring vortex. Two different computational approaches are used: (i) Lagrangian models for the bubble dynamics coupled with direct numerical simulations of the flow field, and (ii) direct simulation of two--phase gas/water bubbles using a front tracking method coupled with the Navier--Stokes equation for the external flow. The Euler--Lagrange simulations assume one--way coupling with non--cavitation nuclei. The talk will discuss the process of entrainment of the bubbles by the vortices, and use the front--tracking simulation results to discuss validity of the model equations used in the Euler--Lagrange simulations.