Rayleigh-Plateau Instability: Revisiting my A-Level Physics


To those of you unfamiliar with the UK education system (pre-1998! I think a little different now), A-levels were what you did between the ages of 16-18 at school. I did Physics, Maths and Chemistry.

The Physics A-Level research project was a pretty big deal. You had to think up something you wanted to study, do some experiments and write them up.

Our teacher was Mr Taylor. He was great. We did not seem to follow any sort of syllabus. We just did Physics for two years and came out top bananas. Lots of radiative stuff. A few explosions. High current electricity. Sparks.

A good friend at school, by far the most talented maths guys I have ever known, looked at the traces of pendulums in 3 dimensions; in other words, the weight on a string is not simply released, its purposely swung away from this arc. He works at Apple now.

Another guy was looking at drag on vary car body shapes. He built a wind tunnel with the models on an electronic balance. He is now important at Jaguar.

Rayleigh-Plateau instability

I looked at Rayleigh-Plateau instability. I did not know that it had a name at the time. This would have been in 1998. Google appeared that same year. I think the only real options were the library and the CD-ROM encyclopedia. I know I never came across Rayleigh Stability in either of these. Beyond getting some cool high-speed camera shots and procrastinating about the free surface energy of a sphere vs a cylinder, I never really answered my own question, and I have regularly (daily) wondered about the answer ever since.

Enough nostalgia.

Rayleigh-Plateau instability describes the tendency for a falling continuous fluid stream to break up into droplets at some threshold. Half of the world’s population witness this phenomenon daily and many have probably wondered why it happens, as I did as an 18-year old. No doubt Joseph Plateau in 1873 and Lord Rayleigh, shortly after, did too. I feel both of these characters really warrant a moment of your time: plateau essentially laid the carpet for TV and Rayleigh explained why the sky was blue, amongst other things.

The rest of the world’s population (the ones that do not stand up), actually ALL the population, experience the effects of Rayleigh-Plateau instability wee spatters on the floor when the droplets hitting porcelain.

This does not excuse puddles, which can not be explained by this phenomenon.

This post is really intended to be a placeholder. Some day I am going to sit down and do the maths and finish that A-Level project! Not today though.