Pressure-controlled displacement of an oil-water interface is studied in dense packings of functionalized glass beads with well-defined spatial wettability correlations. An enhanced dissipation is observed if the typical extension $\xi$ of the same-type wetting domains is smaller than the average bead diameter $d$. Three-dimensional imaging using x-ray microtomography shows that the frequencies $n(s)$ of residual droplet volumes $s$ for different $\xi$ collapse onto the same curve. This indicates that the additional dissipation for small $\xi$ is due to contact line pinning rather than an increase of capillary break-up and coalescence events.

• Received 27 June 2014

DOI:https://doi.org/10.1103/PhysRevApplied.2.034002