Figure 3-35

Liquid in a channel with a bulge.

The contact angle on all surfaces is 30 degrees, so Concus-Finn filaments can form form. When the filament tips reach the entrance to the bulge, there is a brief pause at the sharp corner until the floor contact line makes it just into the bulge, so the filament tip can make it around the corner. As the channel widens, the bulk flow stops and only the filaments continue. But as the filaments reach the exit of the bulge, the bulge starts to fill in. If the evolution is continued beyond the end of this animation, the filaments merge and the channel completely fills in.