Figure 2-27-C: Filaments moving down channel with enlargements, not merging

Channel with three bulges.

The narrow parts of the channel are narrow enough to support bulk liquid progress, and narrow enough that separate Concus-Finn filaments cannot form. The bulges are too wide for bulk progress, so the filaments separate there and re-combine beyond the bulge. This time, the walls are high enough that once the filaments merge at the bulge exit, backfill can completely cover the bulge floor. There is no stable catenoid shape that fits walls this high. The contact angle on all surfaces is 30 degrees, so Concus-Finn filaments can form. The walls have been raised more from Fig. 2-27-B.