Fingering instabilities of a reactive micellar interface.
We present an experimental study of the fingering patterns in a Hele-Shaw cell occurring when a gel-like material forms at the interface between aqueous solutions of a cationic surfactant (cetyltrimethylammonium bromide) and an organic salt (salicylic acid), two solutions known to form a highly elastic wormlike micellar fluid when mixed homogeneously. A variety of fingering instabilities are observed, depending on the velocity of the front (the injection rate), and on which fluid is injected into which. We have found a regime of nonconfined stationary or wavy fingers for which width selection seems to occur without the presence of bounding walls, unlike the Saffman-Taylor experiment. Qualitatively, some of our observations share common mechanisms with instabilities of cooling lava flows or growing biofilms.
Podgorski
Thomas
T
W. G. Pritchard Laboratories, Department of Mathematics, Penn State University, University Park, Pennsylvania 16802, USA.
Sostarecz
Michael C
MC
Zorman
Sylvain
S
Belmonte
Andrew
A