Two Vortex Rings Colliding in SLOW MOTION - Smarter Every Day 195

[Gasps] Was it -- that was it, wasn't it? I think we've been doing it so long we don't know what perfect looks like. [Laughs] What's up, I'm Destin. I do not even know how to start this video. I'll just try to explain it and -- I mean, this is a huge deal.

Five years ago, someone sent me a link and I opened it, and I love fluid dynamics and this was cool. It was like this lab video from Australia of two vortex rings colliding, and they did this really weird thing, and then these other rings poked out, and I was like "Oh, that was -", and my brain didn't even understand. So I hit refresh, and refresh, and refresh.

And the more I watched it, the more I realized, this is really special. Like there's some complex fluid mechanics going on here that needs to be understood. So, I started Googling, because that's what you do. I want to learn more about it, and I found some research papers where people had numerically tried to figure it out, but nobody's actually done it. Why?

So I started trying to do it myself. That didn't work, at all. I started trying to get help. So I got some undergraduate research students to help. They had some limited results. But it's a very difficult problem. So at this point, I realized: this is serious. I mean, this has not been recreated since cameras looked like this, right? So you can't Google it, money can't buy it.

If I ever want to see it better than this [gestures to camera], I have to do it myself. So I used some Patreon funding, and I went to this friend of mine. He's a motion control engineer. His name is David Lenderman. We've been working on this for well over 3 years. I mean, this has descended into madness. We've created all different types of prototypes.

I don't know how to explain why, other than, "This had to be done." So I wanted to see the vortex collision, recreated with modern imagery technology. And that's what this video is. I hope you enjoy it.

So, in 1992 in the journal "Letters to Nature," there was an article written by Doctor T. T. Lim. Now you see this right here on the toolbox in David's shop, because for the past year, we've been trying to recreate this device. It's a device he created--you may have seen the video-- two vortex rings collided together, and they created these secondary rings that came off the edges.

Now the problem with this is, it was filmed with a potato. We're going to use this, it's a Phantom v2511, and the goal here is to get those secondary rings. [MUSIC] You have an electromechanical actuator that's driving a pneumatic cylinder, which is pumping air to a valve so that you can control the input to both cylinders at the same time.

DAVID: Right, which seems to be fairly effective and predictable.

DESTIN: So it's basically a very precisely calibrated syringe with a stroke of a certain throw, OK.

DAVID: It's more of a messy process.

DESTIN: I'm ready.

DAVID: Doesn't look bad for the first one.

DESTIN: That wasn't bad. How do you change the water?

DAVID: Pump it out.

DESTIN: That is impressive. You want to do the mixing routine? Really good one on that side. [MUSICAL IMPACT]

DESTIN: Ohhhh it's pretty.

DAVID: That was a good one.

DESTIN: That was pretty. [GASP] When you get done with a shot, it looks like you're growing your own organs in the aquarium.

DESTIN: Opening... [BOTH EXCLAIM] Ohhh, I triggered on that. So this is what, this is round how many? Five? Four? Seven? [CHUCKLES] [MUSIC CONTINUES] 750... We are refilling the tank for the hundred somethingth time. It's going to work. That is going to work. Oh, I think today might be the day. [MUSICAL IMPACT] Haha, got the secondaries. Look at those, man. Wow [MUSIC CONTINUES]

I started this process simply wanting to recreate something that captured my imagination. But obviously it morphed into something much larger than that. It wasn't about fluid dynamics or motion control. It was about patience and persistence. The value of surrounding yourself with people who get this cannot be overstated.

David wouldn't quit, which taught me to power through, even when it might not make sense on paper. Every time we failed, we learned something. So ask yourself this: What are you too intimidated to try? All you gotta do is fill the tank back up, and give it another shot.

So three years, and a bunch of ink in an aquarium? No, this is so much more than that -- this is what taught me persistence. For you, example, what is your vortex collision? Is it something at school that's hard, a subject? Is it a project at work that you don't think you can overcome? Is it some skill you want to learn? What is the thing you have to overcome, and how are you going to do it?

The payoff here was visual data that was not filmed with a potato. This is a big deal, because we can now see things we could never see before. For example, if you look closely, you can see as the outer ring of the vortex starts to break up, you get these little nodules that have a low-pressure spot right in the middle.

And Don Pettit, an astronaut, his theory is that, that low-pressure zone starts to suck material away from the outside perimeter, breaking up the ring into regular intervals. The next part, however, remains a mystery: how does that, once it breaks up, turn 90°, and turn into a ring facing outwards? That is the mystery, and now we have the visual data to look at it.

You can see that over on the second channel, I have twelve hours of footage of everything we recorded, it's all there, go check that out if you're interested in seeing how all this stuff works.

I want to say thanks to the sponsor, which is Audible. You can get an audio book for free by going to or texting the word: "smarter" to 500-500. I recommend the book "Letters to a Young Scientist" by E. O. Wilson. He's an amazing Pulitzer Prize-winning author that tells you at the end of his career, tells you young scientists what path you should take, and how you should go about it.

You can listen to this entire book on one road trip, or just a couple of commutes. I highly recommend "Letters to a Young Scientist" by E. O. Wilson, get that by going to: You get that book for free and a thirty-day free trial, or you can text the word: "smarter" to 500-500, and they'll send you a link.

OK, I hope you enjoyed this video, I hope it earned your subscription. Obviously, this was a lot of work, I would love it if this was the video that you started the subscription to Smarter Every Day on, that would be awesome.

Anyway, big thanks to David, thank you to Gordon from A Shell In The Pit for writing this song specifically for this video, and also to the patrons who have supported Smarter Every Day in the background for years, and let me do long, drawn-out projects like this, it's fantastic.

I learned a lot, I hope you did too. I'm Destin, you're getting Smarter Every Day, have a good one, bye. Hey, on the way out here, a lot of times people will share a video like this in the form of GIFs, and this took so long and so much effort. I would really appreciate it if you'd get people here to the channel by sharing the entire video, that is such a big help.

Patrons, I left the hi-res images of these shots on Patreon so you can print those out and stare at them like I do, 'cause they're awesome. Thank you so much for enjoying this with me, I appreciate ya. Bye.