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Effect of Dispersion on Solutal Convection in Porous Media
Author(s) -
Liang Yu,
Wen Baole,
Hesse Marc A.,
DiCarlo David
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl079849
Subject(s) - convection , buoyancy , dispersion (optics) , porous medium , flux (metallurgy) , materials science , anisotropy , mechanics , rayleigh scattering , mass flux , dissipation , porosity , physics , thermodynamics , optics , composite material , metallurgy
Solutal convection in porous media is thought to be controlled by the molecular Rayleigh number, R a m , the ratio of the buoyant driving force over diffusive dissipation. The mass flux should increase linearly with R a m and the finger spacing should decrease as R a m − 1 / 2 . Instead, our experiments find that flux levels off at large R a m and finger spacing increases with R a m . Here we show that the convective pattern is controlled by a dispersive Rayleigh number, R a d , balancing buoyancy and dispersion. Increasing the bead size of the porous medium increases R a m but decreases R a d and hence coarsens the pattern. While the flux is predominantly controlled by R a m , the anisotropy of mechanical dispersion leads to an asymmetry in the pattern that limits the flux at large bead sizes.