Interfacial Fingering Instabilities in Simple Two-Component Systems

Two experiments were performed studying interfacial instabili- ties. In the first of these experiments, the interface between the two phases of a binary liquid mixture is examined for unstable growth after the mixture is quenched further into its two phased region. Never is any dramatic growth observed, but under conditions of small dimensionless quench depth ((theta) < 1.5 (.) 10('-3)), the intensity of light scattered from the interface grows for small values of the momentum transfer, k. In the second of these experiments, measurements of radial fingering patterns have been performed over a range of dimension- less force parameter 1.1 (LESSTHEQ) C (LESSTHEQ) 35. All observed flows show a power law dependence of radius of gyration on area with exponent 1/1.79. Local curvatures provide the best characterization of pattern ramifi- cation. The power spectra of these curvatures are used to define an average wavenumber (')K. A scaling is observed to collapse dimen- sionless average wavenumber ((')K') versus dimensionless area of the mixing zone onto one function which rises early in the flows then coarsens as the flows become more developed.