Gallery of scientific pictures and videos
-
Meanders on a partially wetting incline [2016-01-24]
It’s always fascinating to watch a small rivulet of water slowly creep across the plane (it can last for over an hour) and change its path, growing new bends, as if it were a river shifting its bed. When finally the pattern becomes stationary, the turning radius is given by the wetting properties of the substrate. It is the tightest bend the water that makes up the rivulet can follow, given its velocity, without sliding outwards. At the end it looks as if it was swaying left and right in the same manner as a skier on a slope of fresh powder snow.
-
Cross-hatched erosion pattern on a beach [2015-12-30]
The receding swash on this beach creates grooves not along the direction of steepest slope, but at a well defined angle to it. This results in a cross-hatched pattern reminiscent of what we observed in a [laboratory erosion experiment][erosion] at weak slopes in powder layers. -
Water drop on a hydrogel [2015-10-24]
Coalescence of water drops on the surface of an Agar hydrogel. Similar to the previous post, but less symmetric. -
Water drop on a hydrogel [2015-10-08]
This photograph shows a small water drop resting at the surface of a hydrogel (Agar). The transparent drop is made visible through the deformations of a grid of black lines placed behind the drop. Surprisingly enough, the drop only partially wets the gel which contains more than 99% of water, instead of completely spreading. The strip-videograph below shows how, within minutes, the drop slowly disappears into the gel, first by flattening with fixed contact lines, and then by shrinking in diameter. This illustrates that a gel can be seen as a sort of molecular sponge that can take up its solvent. Notice how the gel around the drop is swelling.
Space-time diagram (aka strip-videograph, aka kymograph) showing a horizontal line through the centre of the drop above, evolving with time (time progresses from top to bottom).
Last modified: 18 Jul 2020