Making Rayleigh-Bénard Convection Cells

A simple self organising phenomenon!

So today I made Rayleigh Benard cells. This is a cheap demonstration of organising behaviour in a fluid.

I read about this experiment when reading about Lorenz’s history in Chaos by Gleick. Lorenz initially derived his chaotic strange attractor when looking at simplified versions of fluid convection. I’ll write another post on the theory later. For now, I’ll write about how to do it and show my results.

I got silicone gel, mica powder, a hot plate, and a borosilicate petri dish. I used 50 cSt High Temp Silicone Fluid, like this:

Then I just got the regular mica powder from Amazon.

I then put the oil in a borosilicate petri dish, a pinch of the mica powder, and then mixed it pretty thoroughly to get it even.

Then I heated it the mix using my cheaper hot plate that I got from Alibaba. At first, some discrete cells started to form, both and the middle and the sides:

You can see the boundaries start to form:

And then after a while the cells start to get really organised, even after I cooled it down.

Whilst the experiment is simple I think there are endless interesting questions.

• Is it easy to predict or model the size of the cells when it settles?

• Do the number of cells depend on how quickly the temperature was increased?

• What temperature do the cells break down and turbulence arises?

• Are the number of cells dependent on the steepness of the temperature gradient?

I also wanted to figure out a better way to automate the process here. I was thinking of attaching a camera on bird’s eye view and then doing some image segmentation over a long time periods to see the evolution. I also wanted a way to program my hotplate to control the temperature gradients.