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Hello,

I am modeling the effect of the wind in a bay. I don't know which type of spectrum I have to use in the boundary conditions and in the initial conditions.

Thanks a lot for you time,

Andres

Hello Andres,

you can read the §8.4 and §8.5 of the documentation to know how to prescribe the initial and boundary conditions in Tomawac.

For the initial conditions, you can start from a calm sea-state (no wave) if you set the keyword LINEAR WAVE GROWTH to 1 (otherwise you wont get any wave in your domain).

For the boundary conditions, you can put a free boundary (=2 in your boundary conditions file) that fully absorbs the wave energy at your solid boundary and a prescribed value (=5) at the points where you want that the wave energy enters the domain. Please refer to Table 8.1 of the documentation to see the type of boundary directional spectrum to impose (=1-7) at the boundary. If you know the significant wave height (BOUNDARY SIGNIFICANT WAVE HEIGHT), main direction (BOUNDARY MAIN DIRECTION 1) and peak frequency (BOUNDARY PEAK FREQUENCY) of your waves, you can choose TYPE OF BOUNDARY DIRECTIONAL SPECTRUM = 6. You will also have to give the directional spreading (BOUNDARY DIRECTIONAL SPREAD 1) of your spectrum.

I hope this answers your question.

Best regards,

Elodie

Hello

If you want more information about the conditions for a type 6 spectrum, you can check the following topic :

www.opentelemac.org/index.php?option=com...9&id=2616&Itemid=177

Best regards

Thomas

Thank you very much,

I have turned the model but the wave height that I found with the model is almost two times smaller than the wave height of Bretschneider equation and if I change the WAVE GROWTH LIMITER to 2 (like is suggested in 6.3.2) then the wave height of the model becomes 3 times higher.

Hello,

which model do you use for the generation by wind and the dissipation by whitecapping?

Do you have a strong wind? (for strong values of the wind, there can be an overestimation by the Janssen (1991) model for wind generation combined with the Komen (1984) dissipation.

Elodie

hello

The function f=f0*r^(k-1)" for k=1..NF plays a big role in the wave generated by the wind (see the keywords "nombre de fréquences", "raison fréquentielle" etc...). Be sure that the period generated by your wind is in included in your frequence spectrum.
It is also important to look at the time of the blowing wind. The more the time of blowing is long, the more the value of Hs should be high.

Thomas

Hello

I was using the Janssen's model to generate the wind but I wasn't taking into account the dissipation by whitecapping. When I use it I get more accurate results.

Regards

Andres

Ok. You can also try to use the Snyder et al. model (WIND GENERATION=2)combined with the whitecapping dissipation of Westhuysen et al. (WHITE CAPPING DISSIPATION =2) and see what it gives you.
Regards,
Elodie