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Look at the picture below enter image description here

I know about plateau rayleigh instability. And my opinion is that the reason of this phenomena is plateau rayleigh instability. But there's a question, in the picture above, imagine that we hadn't put any surface on the way of liquid column, then we wouldn't see any of these stationary waves, and the liquid column will continue until it change to drops. BUT, when we put the surface on the way of it, we'll see these waves. and these waves are just seen in the presence of an obstacle.

So, What does the obstacle ( that we put on the way of liquid column to get these waves ) do, that cause these waves?

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Edit: please see duplicate answers as well

This could be a hydrodynamic instability known as the Rayleigh-Plateau instability.

In short, liquids, because of surface tension at the liquid-gas interphase, tend to minimize their surface area. A liquid column of volume $V$ always has a larger surface area than $n$ droplets of volume $V/n$.

As it turns out the length at which point the liquid column will start to break up is found by the heuristic: $$\kappa R_0 \approx 0.697$$ where $\kappa$ is the wave number and $R_0$ is the initial radius of the column.

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  • $\begingroup$ Really thank you. seems scientists have worked on it and it's not something new. $\endgroup$
    – David 2000
    Commented Sep 10, 2015 at 15:43
  • $\begingroup$ I've got a question, why does it happen when collision with a surface $\endgroup$
    – David 2000
    Commented Sep 11, 2015 at 16:20
  • $\begingroup$ @David2000 - My guess: The collision with the wall introduces some asymmetric pertubation which results in the instability occuring sooner than predicted based on the heuristic. $\endgroup$
    – nluigi
    Commented Sep 11, 2015 at 16:25

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