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DY: Fachverband Dynamik und Statistische Physik
DY 40: Posters II
DY 40.13: Poster
Donnerstag, 17. März 2011, 17:00–19:00, P3
Pattern evolution in a lifted Hele-Shaw cell — •Julia Nase1,3, Didi Derks2, and Anke Lindner1 — 1PMMH-ESPCI, 75231 Paris Cedex 5, France — 2Graduate School of Engineering, Osaka University, Japan — 3Fakutät Physik/DELTA, TU Dortmund, 44221 Dortmund
When a liquid is confined between two plates and the upper plate is lifted at constant speed, air penetrates into the liquid volume from the sides. For certain conditions, the contracting liquid does not form a stable circle, but air fingers develop. This instability is a variant of the Saffman-Taylor-instability and has the particularity to take place at changing control parameter. This situation is important for the understanding of debonding mechanisms in adhesion problems and might also give insight into growth mechanisms in biological systems.
We investigate the evolution of the finger pattern from the moment of destabilization to the final plate separation in a Newtonian liquid. At fixed time, the pattern is characterized by the number of fingers and the finger amplitude from tip to base. Starting from a variation of the parameters lifting speed v0, initial gap width b0, cell radius R0, and fluid viscosity η, we investigate in depth the influence of these parameters on the pattern coarsening.
At each moment, we distinguish stagnant and growing fingers. We show that the number of growing fingers is well described by a purely linear theory. Surprisingly, this description is also valid at late times where the linear prediction usually is expected to fail. The total number of fingers and the amplitude, however, are determined by the exact experimental conditions, particularly by the cell geometry.