Vortex ring impingement on a porous convex semi-cylindrical wall

Abstract

Vortex ring impingement on a porous convex semi-cylindrical wall was examined experimentally to clarify how permeability and curvature jointly redistribute vortical material. A single vortex ring at a Reynolds number of 1000 was directed toward models with porosities ϕ = 46%, 59%, 65%, and 68%. Planar laser-induced fluorescence visualization was used to track the dye-marked vortex morphology, particle image velocimetry provided the corresponding velocity and vorticity fields, and finite-time Lyapunov exponent fields identified in-plane material-stretching ridges associated with projected wall-side recirculation and through-wall transport. Across the model series, higher porosity and the associated increase in pore scale weaken the upstream residual primary vortex ring and coincide with earlier formation of downstream vortex pairs. The low-porosity case is characterized by delayed leakage and persistent wall-side circulation, whereas the higher-porosity cases show more direct pore-mediated passage. The measurements show how porosity and curvature affect different parts of the interaction. The more open models allow downstream transmitted structures to appear earlier and with clearer organization, whereas the convex surface redirects retained material along the arc and side edges.