Data di Pubblicazione:
2007
Citazione:
Nondiffusive decay of gradient-driven fluctuations in a free-diffusion process / F. Croccolo, D. Brogioli, A. Vailati, M. Giglio, D.S. Cannell. - In: PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS. - ISSN 1539-3755. - 76:4(2007 Oct 05), pp. 041112.041112.1-041112.041112.9.
Abstract:
We report the results of an experimental study of the static and dynamic properties of long wavelength concentration fluctuations in a mixture of glycerol and water undergoing free diffusion. The shadowgraph method was used to measure both the mean-squared amplitude and the temporal correlation function of the fluctuations for wave vectors so small as to be inaccessible to dynamic light scattering. For a fluid with a stabilizing vertical concentration gradient, the fluctuations are predicted to have a decay rate that increases with decreasing wave vector q, for wave vectors below a cutoff wave vector qC, determined by gravity and the fluid properties. This behavior is caused by buoyant forces acting on the fluctuations. We find that for wave vectors above ~qC, the decay rate does vary in the normal diffusive manner as Dq2, where D is the mass diffusion coefficient. Furthermore, for qqC we find that longer wavelength fluctuations decay more rapidly than do shorter wavelength fluctuations, i.e., the behavior is nondiffusive, as predicted.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Diffusion ; fluctuations ; light scattering ; liquid mixtures
Elenco autori:
F. Croccolo, D. Brogioli, A. Vailati, M. Giglio, D.S. Cannell
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