(549g) Parametric Study of Drop Motion Through a Narrow Orifice

In many natural as well as industrial applications, such as geological CO₂ sequestration, underground oil recovery, and other porous media flows, drops move through a solid constriction by displacing a continuous liquid. Both the constriction geometry and the wettability of the surface influence the drop motion in such flows. In this study, we simplify the constricting structure to a thin plate with a circular orifice with orifice-to-drop diameter ratio d/D<1. Drops of water/glycerin with Bond number (Bo) 2-10, released above and axisymmetric to the orifice, encounter the plate after reaching terminal speed. We examine the effects of Bo, orifice-to-drop diameter ratio (d/D), orifice edge geometry (rounded/sharp) and surface wettability (hydrophobic/hydrophilic) on the passage of the drop using high-speed imaging. It is observed that the rounded edge prevents direct contact of drops with the orifice surface, and the subsequent dynamics are unaffected by the surface wettability. By contrast, sharp-edged orifices yield contact between drop and orifice, and the surface wettability influences the subsequent dynamics.  We generate regime maps for different d/D and Bo delineating domains of drop capture, release, and release with breakup.  In sharp-edged orifices, pinning of contact lines at the edge leads to an overall slowing of drop motion. This leads to some additional captures of drop compared to round-edged case. For sharp-edged hydrophilic case, a fraction of drop is always captured at the orifice due to strong wettability of the surface.