75th Annual Meeting of the APS Division of Fluid Dynamics (November 20, 2022 — November 22, 2022)

V0018: Vortical cleaning of oil-impregnated porous surfaces

Authors

• Siddhant Jain, Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, KA 560012, India.
• Shubham Sharma, Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, KA 560012, India.
• Durbar Roy, Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, KA 560012, India.
• Saptarshi Basu, Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, KA 560012, India.

DOI: https://doi.org/10.1103/APS.DFD.2022.GFM.V0018

We investigate the cleaning mechanism of an oil-impregnated porous surface by utilising a
novel method of vortex ring interaction. The kinetic energy of a vortex ring is exploited to
expunge out the trapped oil from the spherical beads based porous surface. The qualitative
and quantitative measurements were made using high-speed shadowgraphy imaging,
Planer Laser-Induced Fluorescence (PLIF) imaging, and Particle Image velocimetry
(PIV) techniques. The interaction phenomenon is first explored from the perspective
of vortex ring dynamics and followed by the oil sheet dynamics. Five different strengths
of vortex ring (characterised by circulation (Γ) based Reynolds number (Re_Γ = 2550 -
14260: Re_Γ = Γ/ν: ν is the kinematic viscosity) and two types of surface porosity (ϕ)
(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 the
surface cleaning takes place from both upstream and downstream regions of the porous
surface. The vortex rings with higher Re_Γ can expunge more oil through a chaotic
interaction process involving Rayleigh-Taylor and Rayleigh-Plateau type instabilities.
However, along with Re_Γ, the interaction dynamics depend strongly on the shape and ϕ
value