When Vortex Rings Collide

Intrigued by a grainy video from 1992, [Destin] from Smarter Every Day decided to jump in and fund his own research into the strange phenomenon of vortex ring collisions.

This hack started with a scientific publication and a video from back in 1992. The paper, written by Dr. T T Lim and TB Nichols, illustrated what happens when two vortex rings collide perfectly head-on. The rings collide and spread out forming a thin membrane. Then smaller rings form at a 90-degree angle to the original collision. It’s a beautiful effect when created with multicolored dye in water. But what causes it? There are theories about the fluid mechanics involved, but not much research has gone on since Dr. Lim’s paper.

[Destin] wanted to find out more about the effect, and get some video of it. Being the guy behind Smarter Every Day, he had the high-speed photography equipment and the funds to make that happen. Little did he know that this passion project would take four years to complete.

The initial prototype was built as part of a senior design project by a group of college students. While they did show the phenomenon, it was only barely visible, and not easily repeatable. [Destin] then got an engineer to design and build the experiment apparatus with him. It took numerous prototypes and changes, and years of development.

The final “vortex cannons” are driven by a computer controlled pneumatic cylinder which ensures both cannons get a perfect pulse of air. The air pushes a membrane which moves the dye and water out through an orifice. It’s a very finicky process, but when everything goes right, the result is a perfect collision. Just as in Dr. Lim’s video, the vortexes crash into each other, then form a ring on smaller vortexes.

Destin didn’t stop there. He’s made his data public, in the form of high-speed video – nearly 12 hours worth when played at normal speed. The hope is that researchers and engineers will now have enough information to better understand this phenomenon.

You can check out the videos after the break. If you’re a Smarter Every Day fan, we’ve covered [Destin’s] work in the past, including his backwards brain bike and his work with magnets.

34 thoughts on “When Vortex Rings Collide

  1. Great persistence, great results and great presentation!

    And I like the random bit “and here’s Astronaut Don Pettit, giving some ideas” ;)
    If anyone actually goes through the 12 hour megacut, is there more footage with Don?

    Also, is there a search function for YouTube comments?

    1. How should that be possible? There is no gas that can create these vortex rings. And even if you put a vortex cannon into space (which exhausts a stream of gas), the rings will have nothing to push against and soon will vanish.

      1. You could have a vortex ring in space if you use gravitational forces to replace the cohesive forces of liquids. There is no reason you can’t have a ring of material in space rotating about the axis of the ring with the gravitational mass of the ring preventing the material from leaving. It would not be stable forever, but neither are vortex rings suspended in liquids and gases.

          1. If our universe is a vortex ring? Then perhaps it is in the process of a collision with another vortex universe. Explaining why it is expanding increasingly faster? It appears that during the collision and formation of the disk membrane, acceleration occurs to the point of the formation of the minor vortex’s. As both rings have approximately the same forward momentum at the collision point, the energy can only be transferred outward. For lack of knowledge, I will say this energy is then combined with the swirl in the rings, angular momentum? This additional energy peaks and forming the minor rings and spending the last of this energy against the buoyancy of the fluid? I am not a scientist, mathematician nor an engineer. Please don’t beat me up if this is a ridiculous thought.

    2. You’d have to operate at a whole different scale (orders of magnitude different). Others are saying space is a vacuum, but of course that’s not true. It’s full of stars, planets, and nebulae. We just don’t have a way to push these around, though. Space also contains “lots” of hydrogen atoms and whatnot, but at very low densities compared to anything earthly.

      1. Space is indeed a vacuum.
        There are different definitions, or grades of vacuum if you prefer, based on particles per volume ranging from 100’s per mL to zero point energy fields.
        As far as vortices I think @deralchemist is correct. If you succeed in creating a vacuum using an artillery piece or vortex canon, the ring will quickly dissipate once it enters the vacuum. You need friction between the two fluids in order to propagate the vortex, without it the ring will scatter according to the momentum of each particle.

  2. Would something like this explain some instances of colliding gas clouds forming stars?
    Or on a larger scale could it explain the distribution of galaxies and/or galaxy clusters in the universe?

  3. I would like to see how their results compare to a theoretically perfect supercomputer simulation of the same fluid dynamics. The later states would be interesting to see the mechanics of.

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