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Soret driven convection in a colloidal solution heated from above at very large solutal Rayleigh number
Roberto Cerbino1, Alberto Vailati, Marzio Giglio
1Istituto Nazionale per la Fisica della Materia (INFM) and Department of Physics, University of Milan, Via Celoria 16, 20133 Milano, Italy.
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.
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