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Periodic boundary conditions (C21 C22 C23)

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Old   November 30, 2021, 13:45
Default Periodic boundary conditions (C21 C22 C23)
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Vahid
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Dear All,
Hello,

Can someone explains C21 to C23 Periodic boundary conditions in DIVEMesh.
I wanted to assign periodic boundary conditions to the side walls of the numerical wave tank (i.e. Surfside2 and Surfside3), so the inclined waves that exit the domain, enter once again from the other side of the NWT. Is this possible in Reeef3D?

Thanks in advance
Vahid
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Old   November 30, 2021, 15:23
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Hans Bihs
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Hi Vahid,

the periodic boundary conditions are suitable for LES simulations. The NWT is not adapted to deal with periodicity. But that should not be a problem for wave simulations, I don't think it is that useful. Let me know what type of simulation you want to perform. Then I could suggest a good alternative approach.
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Old   November 30, 2021, 16:08
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Vahid
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Hi Hans,

Thank you for the response.

I am trying to model the wave propagation on a sloped bed.
I have used the beach type of boundary condition for the side walls of NWT (upper and lower boundaries in the image I attached).
However, as can be seen on the image (the red rectangle), the inclined waves close to the side walls (on the constant elevation part of the bed) are curved toward the walls, which is not correct.
I have changed the side boundaries into no-slip wall and should see the results.

Since in real prototype the waves are infinite along the beach, I was wondering if there is this capability to assign the periodic boundary condition to the side walls, so that all the waves that exit the domain from the upper side once again enters from the lower side of the domain (in other words the wave field will not be influenced by the side walls)?

Best Regards,
Vahid
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Old   November 30, 2021, 16:28
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Hans Bihs
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Hi Vahid,

with this type of scenario, I would recommend not trying to have perfect waves in the whole domain. Instead, assign a working zone where you need the correct waves. Around the working zone, use wave generation and numerical beach relaxation zones as needed.

Another option would be to turn the wave generation relaxation zone so that it is parallel to the incoming wave front.

While it maybe sound like a natural solution for this type of case, periodic boundary conditions would only work well if the free surface would be 100% symmetric, which is actually not the case.
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Old   November 30, 2021, 16:51
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Vahid
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Hi Hans,

Can you explain more about the working zone?
I can imagine to model a more wider area so I can skip the wave deformations close to side walls.
Is this what you mean?

Best Regards,
Vahid
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Old   December 1, 2021, 05:20
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Hi Vahid,

with working zone I mean that you accept that the waves show some wall effects outside a given area. Have you tried to turn the relaxation zone? I think this will improve the curved waves on the right side wall.
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