title: Soret driven convection in a colloidal solution heated from above at very large solutal Rayleigh number.
abstract: Convection in a colloidal suspension with a large negative separation ratio psi is studied experimentally by heating from above. Shadowgraph observations at very large solutal Rayleigh numbers Rtilde; are reported as a function of time. Fast relaxation oscillations are reported for the root mean square value of the shadowgraph intensity. While pure fluids exhibit a transition to turbulent convection for Rayleigh number R approximately 10(6), stable spoke-pattern planform with up and down columnar flows are observed up to Rtilde; approximately 1.9 x 10(9). It is suggested that the surprising stability of the planform against turbulence is due to nonlinear focusing arising from the concentration dependence of the diffusion coefficient.
authors.affiliation: Istituto Nazionale per la Fisica della Materia (INFM) and Department of Physics, University of Milan, Via Celoria 16, 20133 Milano, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Cerbino
authors.forename: Alberto
authors.initials: A
authors.lastname: Vailati
authors.forename: Marzio
authors.initials: M
authors.lastname: Giglio