How to make a knotted vortex ring
Not long ago I posted a short item about the physics of vortex rings. More recently I stumbled across this video that shows how University of Chicago physicists have succeeded in creating a vortex knot—a feat akin to tying a smoke ring into a knot. Linked and knotted vortex loops have existed in theory for more than a century, but creating them in the laboratory had previously eluded scientists. I stole that bit shamelessly from the blurb on Youtube, by the way. I’m not sure whether knotting a vortex tube has any practical applications, but then I don’t really care much about that because it’s fun!
Follow @telescoper
In the Dark 
May 17, 2013 at 8:19 pm
Very interesting: I have a bit of a thing for vortices, in particular the Crow Instability, which is sometimes seen at work in airplane contrails, leading to some fascinating evolving structures.
But is it just me, or do they spend very little time actually showing the knotted vortex? Most of the vortices they generate seem to be rings with ripples in (including the one in the still from the YouTube video above).
You see the knotted vortex generator hydrofoil and the resulting vortex from above once or twice and some simulations, but I would like to have seen more of the knotted one from the side, say.
I wonder then if this was a bit of a rush job PR piece based on very early results, trying to establish precedence 🙂
(Oh, and you like vortices, search for “dolphin bubble rings” on YouTube: stunning.)
May 17, 2013 at 11:11 pm
I posted the dolphin thing a while ago, in the post linked to above. I did a lecture about vortex rings a while ago, and the students loved the video!
May 17, 2013 at 11:21 pm
Indeed; as I was writing my comment earlier, I had an itchy feeling in the back of my skull that this topic had cropped up here earlier … but apparently I was too lazy to even click on the prominently provided link. Cough 🙂