Calculation of Wave Type?


Can anyone clarify this topic for me; I have piston parameters as such:

Which indicates that the generated waves will be of type, "Transitional", but using a LeMehaute diagram as found in this paper;

Where I take according to my understanding; H = 1 [m] (wave height), g = 9.81 [m/s^2] (gravity) and d = 2 [m] (depth), then I find that, I get for y-axis value and x-axis value;

1/(9.81*3^3) = 0.011

2/(9.81*3^3) = 0.022

Which means that I am at around (black marking):

So in theory it is actually a deep water wave?

Then why d/L (depth / lambda) say it is transitional?

Kind regards


  • You made a mistake:

    1/(9.81*3^3) should be ^2

    2/(9.81*3^3) should be ^2

    so the information provided in our file agrees with Le Méhauté abacus ;)

  • Ah I see, thank you, yes indeed a silly one too :-)

    My problem is that I have a resevoir of about 2 m of depth with a span of ca. 60 meters in length, with a piston on the left side and I am trying to generate sufficient conditions for deep water waves. So to do that I am using T = 1.45 s and H = 0.45 m, but then I get this case:

    Where waves never propagate and hit the slope, due to the period being so low I suppose. Maybe it doesn't make physical sense to have deep water waves on this kind of geometry?

    Kind regards

  • @Asalih3d

    Water conditions are defined transitional if the ratio water depth / wavelength ranges between 0.05 and 0.5. That does not define the wave generation order, that is strictly related to the wave linearity but it defines whether we are closer to deep waters (small amplitude waves in big water depths) or shallow waters (where actually the water depth becomes a dominant factor)

  • @Asalih3d

    Your wave tank is very long. Only the horizontal part of it is approx 4 times the wavelength. Wave might decay for some numerical dissipation, if you do not select properly the value of some parameter. I suggest to use coefh=1.8 at least. In any case, it would be better to shorten a bit the domain

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