#granular flow

Researchers sometimes study avalanches and other granular flows in a rolling drum, where grains can cascade down continuously. Here, the twist is that they've done it with photoelastic disks, which show stress patterns when viewed under crossed polarizing filters. (Video and image credit: R. Hodgson et al.)

Even though particles are not (strictly speaking) a fluid, they often behave like one. Here, researchers investigate what happens when two layers of particles--with different size and density--slide down an incline together.  (Video and image credit: M. Ibrahim et al.; via GFM)

Knowing what speed a landslide will reach helps us predict how much damage they can cause. That speed depends on many factors: the steepness of the terrain, the sliding distance, the thickness of the flowing layer, and the type of grains making up the flow. (Image credit: W. Hasselmann; research credit: Y. Wu et al.; via APS News) Read the full article

In "Dispersion," particles spread under the influence of an unseen fluid. Like Roman de Giuli's work, filmmaker Susi Sie creates macro images that look like ice floes, deserts, and river deltas viewed from above. This similarity of patterns at both large and small scales is a specialty of fluid physics. Just as artists use it to mimic larger flows, scientists use it to study planet-scale problems in the lab. (Video and image credit: S. Sie et al.) Read the full article