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Hello!
I want to set a open boundary to let the water flow out the domain.So I set the boundary as 4 4 4.The finite volume method does not have any problems, but the finite element method does not converge
I think the problem is in the boundary condition.Because I change the boundary as 2 2 2,the simulation goes well in FE.
I don't know why this happened
Can someone give me some advice?
Thanks advanced

Hello,

Using code 4 4 4 in the boundary condition file means you let free water depth and the 2 velocity components. The flow may goes out but also comes in.

Depending on the regime of flow (e.g.: subcritical, supercritical), you have to prescribe 0, 1 or 2 informations at the outlet or the inlet. That may create trouble if the boundary condition you have chosen is wrong.

With code 4 4 4, it is often recommended to use Thompson boundary conditions (see keyword OPTION FOR LIQUID BOUNDARIES) to add missing conditions or deal with too many conditions. That may solve your issue.

Anyway, using 2 2 2 in the boundary conditions file means a solid wall and I am pretty sure no water flows out the domain.

If my explanations are not enough, you should upload figures of your issue, it is hard to know what it is really, please read the forum rules, in particular #7:
www.opentelemac.org/index.php/kunena/help

Hope this helps,

Chi-Tuan