Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I don't know hydrodynamics, but I wonder how one would compute resonance modes of a cubic box of water which we shake. I believe the waves would directly depend on the height of water and the width and length of the box. Is it a bit like a waveguide for electodynamics?

share|cite|improve this question
up vote 5 down vote accepted

Yes it is a bit like waveguide for electrodynamics. You've got absolutely the same equation. The difference is in boundary conditions -- instead of Dirichlet you've got to use Neumann boundary conditions.

enter image description here

While of course it works only if you are able no neglect all the non-linear effects -- your waves are low enough.

share|cite|improve this answer
For the smaller wavelengths surface tension also comes into play. – Omega Centauri Jan 31 '11 at 16:34
Well, yes. But you still can linearise this. – Kostya Jan 31 '11 at 16:42
Kosttya, yes you can. The main effect will be that the frequencies versus wavelength plot will have different slopes at short versus long wavelengths. – Omega Centauri Jan 31 '11 at 19:20
Well, of course. But it is irrelevant to my discussion. We are dealing with Laplace equation -- check the reference. There is no time and therefore no frequencies. – Kostya Jan 31 '11 at 20:09

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.