vortex rings

One more Sunday Gunday with Employee Josh C.! “This rifle was a bucket list gun for me for many years. I picked up the Shilen barrel in a Brownells employee auction. Then, I purchased a new Remington 700 SPS chambered in .223 Remington just for the action. Brownells’ own Steve Ostrem cut the barrel to 24”, crowned it and chambered it in .17 Remington Fireball, and it’s the finest machine work ever done for me! I dropped the barreled action into a new Magpul Hunter stock and topped the rifle with Warne bases, Vortex 30mm low rings and a Sightmark Triple Duty 4x16x44 scope. This rifle has now become reality for me!“

In a new ad campaign for paint manufacturer Sherwin-Williams, the production team at Psyop show off some awesome fluid dynamics by swirling and injecting paint underwater. You can see one sequence above, where red and blue paint vortex rings collide head-on before breaking down into a purple turbulent cloud. (What a great way to demonstrate the mixing power of turbulence, right?) Here’s the full 30-second ad clip. Impressively, everything in the video is a practical effect, even the segment that flies past multicolored turbulent plumes. You can see how they filmed everything in their behind-the-scenes featurette below. In the meantime, enjoy the mesmerizing beauty of real-world physics and check out FYFD’s “fluids as art” tag for more examples. (Image and video credit: Psyop for Sherwin-Williams; submitted by Alan B.)

Eyes On Me (Strangers In The Night #8)

AU. Strangers who meet at an underground wrestling match. He is wrestling. She is watching. Sparks fly. 

This was literally buzzing in my head all day and finally I got to it. For alwaysolicity tanyak312 olicityalamode who wanted a wrestling fic. This might not be what you had in mind but I hope you like it :)

| Read the Strangers In The Night Series |


The crowd was getting on her nerves. Her very tight-strung, stretched-almost-to -the-breaking-point nerves. 

Underground wrestling was something she had never even been aware of until the last few months, and even then only because Sara could not stop talking about it. Until yesterday, it had been something distant that she had never had any interest in but had just nodded to in all the right places when Sara talked. Until yesterday. 

This morning, Sara had stopped by her place and literally begged and cajoled Felicity to come with her to the match tonight, pulling out the big and the short and all sorts of guns. 

“I swear if you just come today, I’ll never ever bug you about wrestling again.”

So Felicity had agreed. 

Keep reading

Vortex and rings

The Cassini spacecraft captures three magnificent sights at once: Saturn’s north polar vortex and hexagon along with its expansive rings.

The hexagon, which is wider than two Earths, owes its appearance to the jet stream that forms its perimeter. The jet stream forms a six-lobed, stationary wave which wraps around the north polar regions at a latitude of roughly 77 degrees North.

Image credit: NASA/JPL-Caltech/Space Science Institute

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Drip food coloring into water and you can often see a torus-shaped vortex ring after the drop’s impact. That vortex rings form during droplet impact has been well known for over a century, but only recently have we begun to understand the process that leads to that vortex ring. Part of the challenge is that the vortex formation is very small and very fast, but recent work with x-ray imaging has allowed experimentalists to finally capture this event.

When a drop impacts a pool, surface tension draws some of the pool liquid up the sides of the drop. At the same time, the impact causes ripple-like capillary waves down the sides of the drop. This causes pool liquid to penetrate sharply into the drop, triggering the spirals that mark the forming vortex ring. When drops impact with even higher momentum, multiple vortex spirals can form, as seen on the lower right image. The authors observed as many as four rings during an impact. For more, check out the (open access) article.  (Image and research credit: J. Lee et al., source)

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Vortices are a ubiquitous part of life, whether they’re draining down your bathtub or propelling underwater robots. In the latest video from the Lib Lab project, you can learn about how vortex rings form, what makes them last so long, and even make a vortex generator of your own. I can personally attest that vortex cannons are good for hours of entertainment, no matter your age. They’re even more fun with friends, as the Oregon State drumline demonstrates in the video. Want even more vortex fun? Check out leapfrogging vorticesvortex rings colliding head-on, and a giant 3 meter wide vortex cannon in action. (Video and image credit: Lib Lab)

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Knots have long fascinated humans, appearing in art for thousands of years and generating entire fields of study. Until recently, however, the idea of a knotted fluid was purely theoretical. To knot fluids, researchers used 3D printing to create twisted hydrofoil shapes. When towed through water, fluid travels around the shape and spins up at the trailing edge, creating a knotted vortex ring. The knotted vortices were captured with 3D imaging, allowing scientists to observe how they evolve. So far the knots they’ve created have all been unstable, deforming until two vortex lines approach one another. Upon contact, the vortices disconnect and reconnect with one another, unraveling the knot. Intriguingly, these vortex reconnections seem remarkably similar to the vortex reconnections observed between quantized vortices in superfluids. (Video credit: D. Kleckner et al.)

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physicist porn

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When a droplet falls through an air/water interface, a vortex ring can form and fall through the liquid. In this video, the researchers investigate the effects of a stratified fluid interface on this falling vortex ring. In this case, a less dense fluid sits atop a denser one. Depending on the density of the initial falling droplet and the distance it travels through the first fluid, the behavior and break-up of the vortex ring when it hits the denser fluid differs. Here four different behaviors are demonstrated, including bouncing and trapping of the vortex ring. (Video credit: R. Camassa et al.)

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Behind airplanes in flight, water vapor from the engine exhaust will sometimes condense in the wingtip vortices, thereby forming visible contrails.  The two initially parallel vortex lines are unstable and any small perturbation to them–a slight crosswind, for example–will cause an instability known as the Crow instability. The contrails become wavy, with the amplitude of the wave growing exponentially in time due to interactions between the two vortices. Eventually, the vortex lines can touch and pinch off into vortex rings. The effect is also quite noticeable when smoke generators are used on a plane, and there are some great examples in this air show video between 3:41:00 and 3:44:00. (Video credit: M. Landy-Gyebnar; h/t to Urs)