Rings and Things: The Interactions of Vortices with Sharp Edged Structures and with Each Other

Vortices abound in nature, from “simple” laminar vortex rings generated by some aquatic animals during propulsion, to the highly complex multi-scale structures observed in turbulent flows. As such, vortex dynamics has developed as a subfield of fluid mechanics focusing on the formation, kinematics, and interaction of vortices, as well as their impact on submerged bodies. This seminar will focus on two subclasses of this broad field, namely (1) the interaction of vortices with sharp edged bodies, and (2) the reconnection of adjacent vortex filaments. For (1), we will specifically consider the viscous interaction of vortices impacting fully submerged rigid and deformable plates in two-dimensions. In the particular case of a vortex ring passing through a co-axial aperture in a wall, we will explore an interesting “vortex nozzle” phenomenon, wherein the ring impulse is passively enhanced through the interaction. Regarding (2), we will explore the vortex reconnection process, which has been hypothesized as a potential mechanism behind the turbulent cascade. Previous studies have identified the phases of the reconnection process using anti-parallel tubes with small superposed geometric perturbations. In such cases the vortex tubes do not translate with respect to one another. In contrast, we explore the impact of multiple vortex rings at different collision angles, which influences the rate and completeness of reconnection. The resulting collision dynamics will be discussed in relation to current theories of vortex breakdown.