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Is a motionless liquid-floating object possible?

  1. Aug 17, 2016 #1
    1. The problem statement, all variables and given/known data

    Do you think it's possible for an object to be relatively motionless if floating on rippled water surface?
    Could this be achieved by have it float inside one (or several nested) water/oil-containing containers?

    2. Relevant equations

    ES = - n2(k-m)2 Lucassen's dispersion for capillary waves at a liquid-air interface


    3. The attempt at a solution

    From my (limited) understanding, spilling oil (ugh, poor ecosystems) on water has been a very old trick to dissipate wave energy caused by surface elasticity through the Gibbs-Marangoni effect, however even after scrolling Lighthill's "Waves in Fluids" and reading "The calming effect of oil on water" (Behroozi et al. 2007) I don't yet understand if the tiny amounts measured by Rayleigh (0.81 mg oil spreading on 555 cm^2, or 18mg/square meter) are enough to produce a noticeable dampening effect (compared to a buoy-bound larger amount eventually being thicker) on waves of lower frequencies but larger amplitude (such as those found at sea even on relatively quiet days).

    Unfortunately that study doesn't value the attenuation coefficient of mineral oil (which seemed to me like a inert-enough substitute for successive confined-pond experimentation), so if anybody knows which dampening I'd get (or knows of studies on this), I'd appreciate it.

    Thank you

    Allison
     
  2. jcsd
  3. Aug 17, 2016 #2

    Simon Bridge

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    Since this is listed as homework, there is probably a model of how nested water/oil containing containers may work - or some hint as to how to build such a model.
    You should check.

    Personally I would look at things like impedence matching and interference if you want to make a flat regeon, or maybe find a situation where the motion of two objects wrt the mean liquid level will be in phase.
     
  4. Aug 24, 2016 #3
    Hi Simon, thanks for your reply.
    Unfortunately it's not a real homework but just a project of mine, so I don't have hints to look upon.
    Ok I'll look at these.
     
  5. Aug 24, 2016 #4

    Nidum

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    What is the reality of the problem ? Can you gives us a sketch and some order of magnitude dimensions ?

    There are certainly methods of at least partially stabilising floating bodies in specific situations .
     
  6. Aug 24, 2016 #5

    Simon Bridge

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    Nidum is correct: the answer depends on the specifics.
     
  7. Aug 26, 2016 #6
    You're right, of course here it is.

    [Questionable link deleted by moderator. See the image in post 9 instead]

    Basically just a small-ish floating stand.

    Thank you
     
    Last edited by a moderator: Aug 27, 2016
  8. Aug 27, 2016 #7

    Nidum

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    Please don't click image until mentors have dealt with a reported problem .
     
  9. Aug 27, 2016 #8
    I've uploaded it again, hopefully this works now
    6rocia.jpg
     
  10. Aug 27, 2016 #9

    mfb

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    There are waves with wavelengths much longer than 20 cm. Your device will follow those waves, the details of its construction do not matter.
     
  11. Aug 27, 2016 #10

    CWatters

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    Are you allowed to use a damper? Something like a large horizontal flat sheet of metal on a pole well below the float.
     
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