# vortex ring

Strobing GIF loop of tree rings O.o

Vortex and Rings

js

Transall C-160, vortex

Here we have a “vortex ring” being expelled from Italy’s Mount Etna. These occur because the air in the center moves faster than the air at the edge, which causes a donut shape.

vimeo

For those who see

Vortices are one of the most common structures in fluid dynamics. In this video, Dianna from Physics Girl explores an unusual variety of vortex you can create in a pool. Dragging a plate through the water at the surface creates a half vortex ring, which can be tracked either by the surface depressions created or by using food dye for visualization. Vortex rings are quite common, but a half vortex ring is not. The reason is that, ignoring viscous effects, a vortex filament cannot end in a fluid. The vortex must close back on itself in a loop, or, like the half vortex ring, the ends of the vortex must lie on the fluid boundary. It is possible to break vortex lines like those in smoke rings, but the lines will reattach, creating new vortex rings–just as they do in these vortex knots. (Video credit: Physics Girl; submitted by Tom)

The Ring Around by nsell112 Finally my new Sony A7r2 and New Aquatech Sport Housing arrived and i couldn’t wait to go shoot in the ocean with it. I took this before the sun even came up while shooing underwater towards the front of a wave as it crashes 5 years in front of me and rolls towards me creating a magical look with vortex rings, light ,and lines.

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.)

Building a vortex cannon is a great way to demonstrate the power and longevity of vortex rings. As demonstrated here, it’s possible to create one with just a box with a round hole in it. Adding some smoke or stage fog helps visualize the rings. Vortex rings are found frequently in nature: volcanoes make them, some plants use them to distribute spores, and dolphins and whales use them to play. (submitted by @aggieastronaut)

Dolphins create vortex rings to play with by exhaling through their blowholes.  The sharp impulse of air, combined with the round shape, creates a vortex ring of bubbles. Humans can do this underwater, too, but dolphins aren’t content to lie at the bottom of the pool.  Because smaller vortex rings are more coherent and last longer, they will break the growing vortex so that the vortex fragment rejoins as a smaller vortex ring. They also spin the water nearby to cause wave instabilities in the ring.

Beluga whales and dolphins in captivity have taken to blowing bubble rings to entertain themselves. You can learn how to do the same in the pool. #

Watch on fuckyeahfluiddynamics.tumblr.com

Vortex rings are a topic we’ve covered before with dolphins, whales, humans, volcanoes and even moss, but this video is particularly fun thanks to the addition of a bottle cap. By sticking the bottle cap next to the ring, these swimmers are able to demonstrate the forceful spinning of the fluid near the vortex. This spinning is what helps the vortex hold its shape over distances much larger than its diameter. As you can also see, though, sticking a bottle cap in the ring causes it to break up faster than it would otherwise! (submitted by Kris S)