#pathlines

Over the past 150 years, Switzerland's glaciers have retreated up the alpine slopes, eaten away by warming temperatures induced by industrialization. But such changes can be difficult for people to visualize, so artist Fabian Oefner set out to make these changes more comprehensible. (Image credit: F. Oefner; video credit: Google Arts and Culture) Read the full article

For tiny creatures, swimming through water requires techniques very different than ours. Many, like this sea urchin larva, use hair-like cilia that they beat to push fluid near their bodies. The flows generated this way are beautiful and complex. (Image credit: B. Shrestha et al.) Read the full article

Once again Steve Mould is putting his prototyping skills to use to work out what goes on inside tricky containers. Here he looks at a "magic" wizard's cup where -- like the assassin's teapot -- cleverly placed holes in the side of the cup can block or allow air's escape. In the wizard's cup this lets the wizard refill the cup at will. (Video credit: S. Mould) Read the full article

So much of fluid dynamics is seeking patterns. Shown here are two sets of patterns, each created by a different species of coral larvae.  (Image credit: G. Juarez and D. Gysbers) Read the full article

Notice how the blue and purple lines are relatively straight and oriented in the direction of the flow. This indicates that the flow here is relatively steady and uncomplicated. At the lower heights, though, especially in the green and yellow regions, the pathlines are far more twisted and complex. The flow here is turbulent, and the particles’ trajectories don’t necessarily correlate at all to the winds higher up. (Image credit: T. Japyassu and R. Shnapp et al.; research credit: R. Shnapp et al.; submitted  by Ron S.)

In industry, tanks are often agitated or stirred to mix different elements. The goal is to create a laminar but chaotic flow field throughout the mixture. Introducing particles to such a system reveals that things are not quite as chaotic as they might seem. The photographs above show the pathlines of various large, glowing particles initially poured into the tank from above. Over time, the particles scatter off of structures in the mixed sections of the tank and end up trapped in vortex tubes that form above and below the agitator. Once trapped in the vortex tube, the particles follow helical paths inside the tube, creating patterns like those seen in the lower two photos. (Image and research credit: S. Wang et al., 1, 2, 3)

We're just twisting the plot”