We investigate the early stages of mass convection in a colloidal suspension at high solutal Rayleigh number Ra^s. From the time evolution of shadowgraph images and by assuming a diffusive growth of the boundary layers we obtain an indirect measurement of the concentration boundary layer thickness delta* at the onset of convection. We show that the dimensionless boundary layer thickness delta= delta*/d scales as Ra<sub>s</sub><sup>-p</sup>, where Ras = Ra^sdelta is a modified solutal Rayleigh number for convection which accounts for the actual density unbalance and d is the thickness of the sample layer. This scaling behavior is analogous to that reported at steady state for turbulent convection in simple fluids. We find p = 0.35, a value compatible with the exponent 1/3, reported for turbulent heat convection in simple fluids at steady state.

Scaling behavior for the onset of convection in a colloidal suspension / R. Cerbino, S. Mazzoni, A. Vailati, M. Giglio. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 94:6(2005), pp. 064501.064501-1-064501.064501-4.

Scaling behavior for the onset of convection in a colloidal suspension

R. Cerbino;MAZZONI, STEFANO;A. Vailati;M. Giglio
2005

Abstract

We investigate the early stages of mass convection in a colloidal suspension at high solutal Rayleigh number Ra^s. From the time evolution of shadowgraph images and by assuming a diffusive growth of the boundary layers we obtain an indirect measurement of the concentration boundary layer thickness delta* at the onset of convection. We show that the dimensionless boundary layer thickness delta= delta*/d scales as Ras-p, where Ras = Ra^sdelta is a modified solutal Rayleigh number for convection which accounts for the actual density unbalance and d is the thickness of the sample layer. This scaling behavior is analogous to that reported at steady state for turbulent convection in simple fluids. We find p = 0.35, a value compatible with the exponent 1/3, reported for turbulent heat convection in simple fluids at steady state.
convection ; colloidal suspension ; Soret effect ; instabilities
Settore FIS/03 - Fisica della Materia
PHYSICAL REVIEW LETTERS
http://link.aps.org/abstract/PRL/v94/e064501
Article (author)
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

Caricamento pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/34957
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 42
  • ???jsp.display-item.citation.isi??? 38
social impact