Stick-slip instability for viscous fingering in a gel
Institut Charles Sadron (CNRS UPR22) - 6 rue Boussingault
67083 Strasbourg Cedex, France
2 Laboratoire de Physique Statistique (CNRS UMR 8550), École Normale Supérieure 24 rue Lhomond, 75231 Paris Cedex 05, France
Accepted: 4 March 2002
The growth dynamics of an air finger injected in a visco-elastic gel (a PVA/borax aqueous solution) is studied in a linear Hele-Shaw cell. Besides the standard Saffman-Taylor instability, we observe —with increasing finger velocities— the existence of two new regimes: (a) a stick-slip regime for which the finger tip velocity oscillates between 2 different values, producing local pinching of the finger at regular intervals; (b) a “tadpole” regime where a fracture-type propagation is observed. A scaling argument is proposed to interpret the dependence of the stick-slip frequency with the measured rheological properties of the gel.
PACS: 47.50.+d – Non-Newtonian fluid flows / 82.70.Gg – Gels and sols / 83.60.Wc – Flow instabilities
© EDP Sciences, 2002