flow visualization

2 Articles

Reject Fluid Simulations, Return To Rheoscopic Fluid

August 25, 2026 by 15 Comments

Fluid simulations are one of the “killer apps” of high-performance computing, but if you can’t afford the performance, they can take a depressingly long time to run. Depending on your use case, as long as you keep the Reynold’s number in mind– or are just looking for a qualitative look at pretty flows–you might be able to get away with purely-practical simulations using rheoscopic fluid, as [Visual Thinker] demonstrates in a recent video.

The fluid, as you can guess from the name, lets you scope out rheos— that’s flow, for those of you didn’t take Greek. Making it is as simple as you could ask for: get some mica flakes, which are readily available to add ‘sparkle’ to cosmetics, and mix with water and a drop of soap. The soap isn’t always necessary, but depending on your mica it helps keep it in suspension and avoid clumping– [Visual Thinker] found it helped him a good deal. Being flat plates of reflective material, the mica flakes catch the light and sparkle beautifully– and since they align with the fluid shear, they show you exactly what’s going on in your ‘simulation’.

[Visual Thinker] isn’t starting with serious simulations; the first thing he tries is essentially a toy that lets him see fluid flow around a Benchy by sticking magnets in it and using it to move a cross-section of its hull though a thin layer of fluid sandwitched betwixt pieces of laser-cut acrylic. We don’t call it a toy to disparage it, though– we totally want one. [Visual] mentions the idea of a coffee table combining the concept with the kind of underslung mechanism we see in sand drawing tables, which sounds dangerously hypnotic. If any of you build one, please try and tear your eyes away long enough to let us know.

He has another beautiful piece that make the video worth watching: a wind-tunnel, again made of laser-cut acrylic and printed parts. With careful consideration of the scale and flow speeds, that one might actually prove useful– and even if it doesn’t, it’s pretty enough that it doesn’t really matter. Beauty has its own utility sometimes.

Most wind tunnels we see around here use actual wind, but rheoscopic fluid was invented for this sort of thing, even if it does make for pretty baubles.

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Building A DIY Tornado Tower

April 14, 2025 by 13 Comments

A tornado can be an awe-inspiring sight, but it can also flip your car, trash your house, and otherwise injure you with flying debris. If you’d like to look at swirling air currents in a safer context, you might appreciate this tornado tower build from [Gary Boyd].

[Gary]’s build was inspired by museum demonstrations and the tornado machine designs of [Harald Edens]. His build generates a vortex that spans 1 meter tall in a semi-open cylindrical chamber. A fan in the top of the device sucks in air from the chamber, and exhausts it through a vertical column of holes in the wall of the cylinder. This creates a vortex in the air, though it’s not something you can see on its own. To visualize the flow, the cylindrical chamber is also fitted with an ultrasonic mist generator in the base. The vortex in the chamber is able to pick up this mist, and it can be seen swirling upwards as it is sucked towards the fan at the top.

It’s a nice educational build, and one that’s as nice to look at as it is to study. It produces a thick white vortex that we’re sure someone could turn into an admirable lamp or clock or something, this being Hackaday, after all. In any case, vortexes are well worth your study. If you’re cooking up neat projects with this physical principle, you should absolutely let us know!