Dynamics of a vortex ring impinging on a concave hemicylindrical shell

The interaction of vortex rings with solid surfaces is a classic problem in fluid dynamics, yet their collision with concave hemicylindrical shells remains poorly understood. This experimental study investigates vortex ring impingement on concave surfaces with varying curvature ratios (D${}_{m}$ /D${}_{e}$ = 15,10,5,2,1) at Re=1500. Using planar laser-induced fluorescence and particle image velocimetry, we reveal how curvature controls secondary vortex formation, rotation, and three-dimensional evolution. Dynamic models are proposed to explain the transition from tertiary to secondary vortex dominance as curvature increases, offering new insights into confined vortex-wall interactions.