Valley
Flow
- Strain markers (colored chalk flecks and black Sharpie™ dots)
are clearly visible on the surface of the Flubber.
- Higher velocity in the center of the valley is revealed by
the alternating green and white bands, which deform into “V”s after beginning
the Model Run oriented perpendicular to the long axis of the valley (click to view starting conditions).
- The alternating colored bands make it clear that the outermost
Flubber sticks to the valley walls, creating pure shear that stretches and
thins the Flubber as it flows. Thin, parallel green and white bands
near the valley walls result.
- The alternating green and white bands also reveal that the
Flubber is rolling over itself at the toe due to strong coupling between
the basal Flubber and the plexiglass valley floor. This can be seen
as green bands get drawn under the glacier as it flows down the valley.
Thus, although our numerical analyses are two-dimensional
within the x-y plane, it is clear from the movies that there is a strong
vertical velocity gradient. Velocity approaching zero at the base and
is highest on the Flubber surface. This is similar to glacier flow
when the basal ice is frozen to the substrate.
Piedmont Flow
- Lateral extension during the piedmont- to valley-flow transition
is shown by deformation of the green “V”s into “U”s on the continental plain
and the lateral stretching of air bubbles near the Flubber toe.
- Side shear and rotation along the sandpapered walls on the
continental plain is revealed by the folding of green bands, particularly
along the left wall (looking up-valley).
- The Flubber continues to fold over itself at its toe on the
continental plain.
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