rotating flow


Fire tornadoes, despite their name, are more like dust devils than your typical tornado. In nature, they’ll often form in wildfires, but here the Slow Mo Guys simulate one for the high-speed cameras using a ring of box fans set up to provide rotational flow, or vorticity, around a kerosene fire. As the fire burns, the warm air over the flame moves upward due to buoyancy. This creates a low-pressure area around the fire that draws in the spinning air from further out. Like an ice skater who pulls her arms in when spinning, the rotating air spins faster as it moves in toward the fire, resulting in a swirling turbulent vortex of flame. Hopefully it goes without saying, but, seriously, don’t try this at home. (Video credit: Slow Mo Guys; submitted by Chris S.)

I can’t just give the brush away, it was given to me by someone that asked that it not be distributed, but I can show you how it works.

The brush’s primary function that makes it so useable for me is Rotation. For that to be possible, I’m afraid that you need a stylus that has that functionality.
The Wacom Art Pen has this ability, it’s the best stylus I’ve ever had. Be sure to get one that is compatible with your tablet if you want to do this, they are not cheap. They are usually 60-90 USD.

Secondly, the shape of the brush alpha is rather particular. It’s flat, thinner at the edges so gets a little softer, but I can also use it to make a hard edged line. It’s great to work with, and you could easily make one yourself.
100% opacity, low flow, rotation sense, 16% spacing. Transfer is pen pressure. Smoothing is also checked, which helps a lot.

Hope that helps a little, sorry I can’t give you the brush. :(


One way to explore some of the large-scale atmospheric dynamics we observe here on earth is through table-top demonstrations such as this one. Here a platform with a water tank is rotating at a constant velocity. The camera rotates with the tank; this is why the hand in the video seems to spin. At the center of the tank, ice in a can cools the water, while the warmer air along the periphery provides heating. The green dye marks initially cooler fluid while the red dye marks the warmer fluid from the outside of the tank. The dense cooler fluid sinks and moves outward while warmer water moves in to replace it. This creates radial circulation; the thermal gradients and rotation cause the eddies and jets seen from this top view, in much the same way that they form in the mid-latitudes of earth’s atmosphere.  (Video credit: Marshall Lab, MIT)


Rotating a fluid often produces different dynamical behavior than for a non-rotating fluid.  Here this concept is demonstrated by dropping creamer into a tank of water.  Both experiments produce a turbulent plume, but the way the plume spreads and diffuses is much different in the case of the rotating tank, thanks to the Coriolis effect. (Video credit: SPINLab UCLA)