Confinement effect on the dynamics of concentration non-equilibrium fluctuations
| When |
May 17, 2016
from 10:45 to 12:00 |
|---|---|
| Where | Centre Blaise Pascal |
| Attendees |
Fabrizio Croccolo |
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It is well-known that a macroscopic gradient affects fluctuations in a fluid by making them long-ranged and enhancing their amplitude [1]. The study of fluctuation dynamics by means of Shadowgraph technique [2] reveals that small fluctuations exhibit diffusive lifetimes, while fluctuations larger than a characteristic size live shorter because of gravity, as theoretically [3] and experimentally [4] demonstrated. In this presentation we will report a combination of experimental, theoretical and numerical evidence of a dramatic slowing-down for fluctuations larger than a size dictated by the extent of the system parallel to the gradient [5]. Results from dynamic shadowgraph experiments [4] are complemented by theoretical calculations based on Fluctuating Hydrodynamics [1] and previously developed to investigate the intensity of fluctuations [6], as well as by numerical simulations [7,8]. The experimental data is found to be in excellent agreement with theory and simulations including realistic boundary conditions, demonstrating that the origin of the slowing-down is confinement.
[1] J.M. Ortiz de Zarate and J.V. Sengers, Hydrodynamic Fluctuations in Fluids and Fluid
Mixtures (Elsevier, Amsterdam, 2006).
[2] F. Croccolo and D. Brogioli, App. Opt. 50, 3419 (2011).
[3] P.N. Segrè and J.V. Sengers, Physica A 198, 46 (1993).
[4] F. Croccolo et al., Phys. Rev. E 76, 041112 (2007).
[5] C. Giraudet et al., Europhys. Lett. 111, 60013 (2015).
[6] J.M. Ortiz de Zárate, J.A. Fornés, and J.V. Sengers, Phys. Rev. E 74, 046305 (2006).
[7] F. Balboa Usabiaga et al., SIAM J. Multiscale Model. Simul. 10, 1369 (2012).
[8] S. Delong, et al., Phys. Rev. E 90, 063312 (2014).