Numerical results for fluid flow in a digitized Berea sandstone sample. White, blue, black, and orange represent speeds between 10^-4 and 1 m/s.

From the article:

Pore-Scale Mixing and the Evolution of Hydrodynamic Dispersion in Porous Media
Alexandre Puyguiraud, Philippe Gouze, and Marco Dentz
Phys. Rev. Lett. 126, 164501 (2021)

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