Direct numerical simulation of ventilated vortex breakdown

This research explores the breakdown behavior of two-phase vortices, as found in hydrofoil and propeller wakes using high-fidelity Direct Numerical Simulation. The flow field is initialized with a q-vortex, incorporating a multiphase adjustment proposed by Bosschers [Int. J. Multiph. Flow, 105, 122-133 (2018)], and an isotropic turbulence perturbation. Initially, the study examines the breakdown of a single-phase vortex tube, characterizing the secondary vortex rings and their role in the eventual large amplitude vortex breakdown. Next, this is extended to two-phase vortex behavior and a regime map covering a range of Reynolds and Weber number combinations is produced. The influence of the secondary vortical structures on the interface breakdown is also investigated, and contrasted with the single-phase vortex behavior. The turbulence characteristic is investigated through the turbulent kinetic energy spectrum. Additionally, the evolution of the bubble size population is analyzed to shed light on the ventilated vortex breakdown process.