This planet-like balloon started out as two elastomer sheets, heat-sealed together into a spiraling tube. As the balloon was inflated, it changed from flat to a saddle-like shape. With more air, the pressure inside increased, triggering an instability that caused the middle of the balloon to bulge. As inflation continued, the central bulge expanded, unbonding layer after layer of the seal. Even late in inflation, the balloon maintains hints of its original shape in the form of a ring around the Jovian bulge in the middle. (Image credit: N. Vani et al.)
Category: Phenomena
Etna’s Blowing Rings
Mount Etna has long been known for its smoke rings, but thanks to the opening of a new vent on the volcano’s southeast crater, it’s now making more rings than ever. Etna’s smoke rings are, more precisely, vortex rings — produced in the same way dolphins, swimmers, and whales make vortex rings: a sudden push of air through a roughly circular opening. It’s likely that Etna and other volcanoes make far more rings than those we see; we’re limited to noticing only the ones that entrain smoke and condensation to make them visible. (Video and image credit: The Straits Times; via Colossal)
Millennium Falcon’s Glide
In what seems to be a tradition now, a group at MIT imagined how the Millennium Falcon would perform if it lost its engines during atmospheric flight. Their hypothetical scenario took place in the Battle of Endor, with the Falcon flying at an altitude of 2 kilometers.* Could Han Solo and Chewbecca safely glide the craft down?
Using computational fluid dynamics, the group found the Millennium Falcon has a glide ratio of only 1.8, meaning it travels forward 1.8 kilometers in the time it takes to lose one kilometer of altitude. Its namesake bird, on the other hand, has a glide ratio of 10. The Corellian freighter might not be the best glider out there, but the team estimated that it could safely manage its 3.6 kilometer glide down. (Image credit: S. Costa et al.; see also X-Wing Re-entry and AT-AT Flow)
*I’m definitely overthinking this, but now I’m really wondering what atmospheric characteristics they used for Endor. And what’s Endor’s gravity like?
Kirigami Parachutes
To fly stably, parachutes need to deform and allow some air to pass through their canopy. In this video, researchers investigate kirigimi parachutes, inspired by a form of paper art that uses cuts to create three-dimensional shapes. After laser-cutting, these disks are dropped — or placed in a wind tunnel — to observe how they “fly” at different speeds. Sometimes they flutter or bend; other shapes elongate in the flow. (Video and image credit: D. Lamoureux et al.; via GoSM)
Evolving Fingers
If you sandwich a viscous fluid between two plates and inject a less viscous fluid, you’ll get viscous fingers that spread and split as they grow. This research poster depicts that situation with a slight twist: the viscous fluid (transparent in the image) is shear-thinning. That means its viscosity drops when it’s deformed. In this situation, the fingers formed by the injected (blue) fluid start out the way we’d expect: splitting as they grow (inner portion of the composite image). But then, the tip-splitting stops and the fingers instead elongate into spikes (middle ring). Eventually, as the outer fluid’s viscosity drops further, the fingers round out and spread without splitting (outer arc of the image). (Image credit: E. Dakov et al.; via GoSM)
Bubbles Encased in Ice
If you’ve ever made ice in a freezer, you’ve probably noticed the streaks of frozen bubbles inside the ice. In its liquid state, water is good at dissolving various gases — like the carbon dioxide in sparkling water. During freezing, though, those gases cannot remain in solution; the water simply doesn’t have space between its crystalline ice lattice for non-water molecules. So the gases are forced out of solution, where they form bubbles. The final shape of the frozen bubble depends on the interplay between the speed of a bubble’s growth and how quickly the ice freezes. Here, the researchers used polarized light to outline the bubbles in color, highlighting the wide array of possible shapes. (Image credit: J. Meijer and D. Lohse; via GoSM)
Drops of Fiber Suspensions
To 3D print with fiber-infused liquids, we need to understand how these drops form, break-up, and splash. That’s the subject of this research poster, which shows drops of a fiber suspension forming and pinching off along the top of the image. In the lower half of the image, drops of the suspension hit a hydrophilic surface and spread. How the drop and its fibers spread will affect the final properties of the printed material. (Image credit: S. Rajesh and A. Sauret; via GoSM)
Floating in Sync
Objects on a vibrating liquid bath can interact with each other through the waves they make as they bounce. Here, researchers look at three-armed spinners interacting in pairs and in larger groups. A pair of spinners can synchronize so that they spin together or so that they spin in opposing phases. With more spinners, more complex patterns are possible. The spinners can even “freeze” one another by forming a pattern of standing waves that keep them locked in their orientation. (Video and image credit: J. Barotta et al.; via GoSM)
Mimicking Plant Movement
Many plants control the curvature of their leaves by selectively pumping water into cells that line the outer surface. This swelling triggers bending. Engineers created their own version of this structure by 3D-printing trapezoidal shapes onto a fabric. Then, they heat sealed a second layer of fabric over this, creating airtight channels. When inflated, these channels make the structure bend, allowing them to create complex shapes by selectively inflating different areas. (Image credit: T. Gao et al.; via GoSM)
The Channel Tunnel
To celebrate the 30th anniversary of the Channel Tunnel, Practical Engineering takes a look back at the construction and operation of this incredible piece of infrastructure. This 30-mile-long underwater tunnel began construction in the 1980s, using giant Tunnel Boring Machines to drill out three tunnels, starting from either side and, incredibly, meeting in the middle. All that construction underground (and underwater) is no simple feat, as Grady discusses. He also takes a look at some of the operational challenges of the design, including managing heat and air pressure build-up. (Image and video credit: Practical Engineering)
