Finding Beauty in Asymmetry: Vortex Ring-Hemicylindrical Cavity Interactions

A three-dimensional vortex-ring impinging on a non-axisymmetric cavity produces asymmetric flow behavior. This interaction finds various engineering and biomedical applications. While symmetric vortex ring-cavity interactions have been shown to depend on cavity size, the influence of cavity size on more complex asymmetric interactions is not well understood. Elucidating these physics will enrich fundamental knowledge of vortex ring dynamics while providing insight into specific scenarios of interest; namely, replacement voice via tracheoesophageal speech. The goal of this study is to investigate the effect of cavity size on the physics of a vortex ring impinging on a hemicylindrical cavity. Vortex rings with formation number and Reynolds number were generated in a water tank. Six different ratios of vortex ring radius R_v to hemicylindrical cavity radius were examined; namely, γ = 1⁄4, 1⁄3, 2⁄5, 1⁄2, 2⁄3, & 1. Flow visualization and particle image velocimetry were performed. Due to the asymmetric impact, significantly different flow physics were observed in the two primary planes of interaction (i.e., the axial and radial planes). In the axial plane, the induced secondary vortex ring moved away from the impact surface instead of rotating around the primary ring, and the trajectory of the secondary vortex ring varied as a function of γ. In contrast, in the radial plane the secondary vortex ring completely rotated around the primary ring and moves towards the bottom of the hemicylinder surface throughout the interaction.