Convection in a colloidal suspension with a large negative separation ratio ? is studied experimentally by heating from above. Shadowgraph observations at very large solutal Rayleigh numbers R~ 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?106, stable spoke-pattern planform with up and down columnar flows are observed up to R~?1.9×109. 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.
Soret driven convection in a colloidal solution heated from above at very large solutal Rayleigh number / R. Cerbino, A. Vailati, M. Giglio. - In: PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS. - ISSN 1539-3755. - 66:5 pt 2(2002), p. 055301.055301.
Soret driven convection in a colloidal solution heated from above at very large solutal Rayleigh number
R. CerbinoPrimo
;A. VailatiSecondo
;M. GiglioUltimo
2002
Abstract
Convection in a colloidal suspension with a large negative separation ratio ? is studied experimentally by heating from above. Shadowgraph observations at very large solutal Rayleigh numbers R~ 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?106, stable spoke-pattern planform with up and down columnar flows are observed up to R~?1.9×109. 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.Pubblicazioni consigliate
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