Scaling behaviour in the demixing of a binary-liquid mixture under gravity

Gravity-driven demixing experiments of mechanically mixed binary-liquid mixture are performed at various temperatures. A steady state is observed in which the demixing rate is nearly constant. We find that the droplet size in the demixing zone grows only for a short time. During most of the demixing process, the size of these droplets is stabilized by the flow itself. A relationship between the characteristic demixing time r and the reduced temperature ε is found, ie. τ ~ ε^–θ with θ = 0.54 ± 0.03. A phenomenological model in which the demixing process is considered as a flow through a porous medium is proposed to explain the experimental results.