78th Annual Meeting of the APS Division of Fluid Dynamics (Nov 23 — 25, 2025)

P036: Vortex Ring Blossoming on a Wavy Wall: Wavy Surface-imposed Instabilities in Vortex Rebound

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Vortex rings impinging on wavy walls create secondary vortex structures that blossom at the wavenumber of the surface waviness. The experimental visualization of the interaction with surface wavenumber of six (top right) is shown progressing through time clockwise through the satellite images, while the surface wavenumber of twelve (bottom left) is shown progressing through time in a counter-clockwise order. The primary vortex ring (PVR), of equal Reynolds number for both interactions, is shown using green dye while the secondary vortex ring (SVR) is revealed by coating the surface plate in orange dye. During the formation of the SVR, entrainment of some primary fluid leaves the blooms as orange cores cloaked in green. The effect of surface wavenumber has a clear effect on the geometries of both the primary and secondary structures. These dynamics are directly relevant to the mass, momentum, and heat-transfer characteristics of impinging synthetic jets, where repeated PVR-SVR interactions govern overall transfer efficiency.