We investigate the cleaning mechanism of an oil-impregnated porous surface by utilizing a method of vortex ring interaction. The kinetic energy of a vortex ring is exploited to expunge the trapped oil from the spherical-bead-based porous surface. Qualitative and quantitative measurements were made using high-speed shadowgraphy imaging, planar laser-induced fluorescence (PLIF) imaging, and particle image velocimetry (PIV) techniques. The interaction phenomenon is explored from the perspective of vortex ring dynamics followed by oil sheet dynamics. Five different strengths of a vortex ring [characterized by the circulation ($\mathrm{\Gamma }$) -based Reynolds number (${\mathrm{Re}}_{\mathrm{\Gamma }}=2550$–14 260: ${\mathrm{Re}}_{\mathrm{\Gamma }}=\mathrm{\Gamma }/\nu$, where $\nu$ is the kinematic viscosity)] and two types of surface porosity ($\varphi$) (open area ratio, 0.21 and 0.41) are considered for parametric analysis. The interaction process with oil is divided into three regimes: (i) penetration, (ii) bag formation, and (iii) bag breakup. Depending on the strength of the vortex ring, it is observed that surface cleaning takes place from both upstream and downstream regions of the porous surface. The vortex rings with higher ${\mathrm{Re}}_{\mathrm{\Gamma }}$ can expunge more oil through a complicated interaction process involving Rayleigh-Taylor- and Rayleigh-Plateau-type instabilities. However, along with ${\mathrm{Re}}_{\mathrm{\Gamma }}$, the interaction dynamics depend strongly on the shape and $\varphi$ value. The interaction process is characterized by vorticity cancellation, Kelvin-Helmholtz (KH) instabilities, and three-dimensional interactions.

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• Atomization
• Flows in porous media