VFIN

Many engineering and environmental situations involve vortices and interfaces between two fluids. Situations include the wake of floating bodies or bodies immersed at small depth, where vortices are shed under the water surface, or the wake of propellers and foils where tip vortices may cavitate or trap atmospheric air in their core. In both instances, the presence of an interface located either in the vicinity of the vortex or within its core, crucially modifies the instability and the dynamics of the system. In this project, we aim at gaining some in-depth knowledge on this interaction between vortex and interface. We plan to adapt water channel facilities at IRPHE (Marseilles) and d'Alembert (Paris) to investigate how a foil tip vortex forced at small depth interacts with the air-water surface, is able to trap air bubbles, and how instabilities are affected. In the rotating tank facility at LMFA (Lyon), we will instead create a cylindrical interface between a bubble of light fluid around the axis surrounded by a heavier fluid in near-solid-body rotation. This prototypal experiment is expected to give rise to new resonances between capillary and vortical waves, and to help understand more complex situations. Experiments will be coupled with theoretical modeling (asymptotic theories at IRPHE, linear stability analysis at IRPHE, d'Alembert and LMFA) and direct numerical simulations (Basilisk flow solver at d'Alembert). Scientific outputs are expected on the fundamental side, but also on engineering and environmental issues: the surface signature of immersed or floating bodies (hydrofoils, submarines), the identification of noise sources in vortices (behind propellers, foils) or the aerodynamics of lifting surfaces in the near vicinity of the surface (foils, turbines).