#vortex rings

Vortex rings blown from Mount Etna's vents drift through the dawn light in this beautiful image from Dario Giannobile.  (Image credit: D. Giannobile; via APOD) Read the full article

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Credit: Brad Gemmell, associate professor of integrative biology, University of South Florida

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. (Video and image credit: The Straits Times; via Colossal) Read the full article

Some 20,000 years ago, a massive star blew off a ring of dust and gas that expanded into the surrounding interstellar medium. Later, in 1987, the star exploded as supernova 1987A. That explosion lit the surrounding area, revealing a clumpy ring astronomers have struggled to explain. But a new team believes they have a fluid dynamical answer: the Crow instability. (Image credits: NASA/ESA/CSA/M. Matsuura/R. Arendt/C. Fransson and NASA/ESA/A. Angelich + M. Wadas et al.; research credit: M. Wadas et al.; via APS Physics) Read the full article

When a vortex ring forms, it's often from fluid forced through a round outlet, whether that's someone's mouth, a pipe, or a dolphin's blowhole. But vortex rings can come from other shapes, too. (Image, video, and research credit: B. Steinfurth et al.) Read the full article

When a drop of ethanol lands on a pool of water, surface tension forces draw it into a fast-spreading film. Evenly-spaced plumes form at the edges of the film, then the film stops spreading and instead retracts. All of this takes place in about 0.6 seconds.  (Image and research credit: A. Pant and B. Puthenveettil) Read the full article