Regensburg 2016 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 46: Poster: Wetting, Nano- and Microfluidics
CPP 46.13: Poster
Wednesday, March 9, 2016, 18:15–21:00, Poster B2
Wettability controls immiscible fluid displacement through local interfacial instabilities — Micheal Jung1, Martin Brinkmann1,2, Marta Sanchez de La Lama2, Thomas Hiller2, Stephan Herminghaus2, and •Ralf Seemann1 — 1Experimental Physics, Saarland University, Saarbrücken — 2Max Planck Institute for Dynamics and Self-Organisation
Slow immiscible fluid displacement is studied in a transparent quasi two-dimensional Hele-Shaw cell with cylindrical posts for different wetting conditions of the invading fluid. Employing various combinations of fluids and cell materials allows to cover a range of advancing contact angles θa of the invading fluid between 46∘ and 180∘ in our experiments. In parallel, we performed numerical simulations of the displacement process employing a particle-based method that accounts for wall wettability in the same arrangements of cylindrical posts as in experiments. A cross-over between capillary fingering at high values of θa ≳ 120∘ and stable interfacial displacement at θa ≲ 80∘ is observed in experiments and simulations, and quantified through the front length and the final saturation of the displaced fluid. Analysis of the local displacement processes in experiments and simulations demonstrate that the evolution of the front shape is governed by the local advancing modes for quasi-static interfacial displacement as proposed by Cieplak and Robbins [Phys. Rev. Lett. 60 (1988)]. A comparison of the relative frequency of certain advancing modes reveals a cross-over between cooperative interfacial instabilities for good wetting conditions and non-cooperative instabilities for poor wetting conditions.