Double-diffusive fingering instability of a surfactant-glycerine-water drop in water
Max-Planck-Institut für molekulare Physiologie -
Postfach 500247 D-44202 Dortmund, Germany
Accepted: 28 June 2001
We present an experimental setup that allows easy visualization of single fingers formed by double diffusive convection. This setup consists of a drop (containing water and two solutes) that is injected at the bottom of a dish filled with water. The gravity-driven expansion of the drop induces a toroidal bulk flow of the surrounding water. This flow straightens and confines the fingers horizontally and quasi–two-dimensionally. An extremely low diffusion coefficient of one of the two solutes (a surfactant in our case) causes unusually stable configurations. This stability is robust within a wide range of concentrations. Wavelength measurements agree well with theoretical estimations.
PACS: 47.54.+r – Pattern selection; pattern formation / 47.20.Bp – Buoyancy-driven instability / 66.10.Cb – Diffusion and thermal diffusion
© EDP Sciences, 2001