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Journal Articles Journal of Fluid Mechanics Year : 2022

Phoresis in cellular flows: from enhanced dispersion to blockage

Abstract

In this article, we study numerically the dispersion of colloids in a 2-dimensional cellular flow in the presence of an imposed mean salt gradient. Due to the additional scalar, the colloids do not follow exactly the Eulerian flow-field, but have a (small) extra-velocity proportional to the salt gradient, v dp = α∇S, where α is the phoretic constant and S the salt concentration. We study the demixing of an homogenous distribution of colloids and how their long term mean velocity V m and effective diffusivity D eff are influenced by the phoretic drift. We observe two regimes of colloids dynamics depending on a blockage criterion R = αGL/ √ 4D c D s , where G is the mean salt gradient amplitude, L the lengthscale of the flow and D c , D s the molecular diffusivities of colloids and salt. When R < 1, the mean velocity is strongly enhanced with V m ∝ αG √ Pe s , Pe s being the salt Péclet number. When R > 1, the compressibility effect due to the phoretic drift is so strong that a depletion of colloids occurs along the separatrices inhibiting cell-to-cell transport.
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Origin : Publication funded by an institution

Dates and versions

hal-03619951 , version 1 (25-03-2022)
hal-03619951 , version 2 (15-09-2022)

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Romain Volk, Mickaël Bourgoin, Charles-Édouard Bréhier, Florence Raynal. Phoresis in cellular flows: from enhanced dispersion to blockage. Journal of Fluid Mechanics, 2022, 948, pp.A42. ⟨10.1017/jfm.2022.730⟩. ⟨hal-03619951v2⟩
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