open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

I find that there are two ways to define the open boundary(as shown in attachment), but I don't quite understand the main difference between these two, and which one to choose for a specific case...

Can any experienced user give me a hint,
thank you very much in advance.

Best regard!

Hello,

There is not much difference between those two ways, except that you have corners in one case, and I would favour another criterion. Since open boundaries in the sea are generally not well posed (people often prescribe the free surface elevation and do not know the velocities). The practical trick to avoid problems is to have open boundaries with deep waters so that the velocities are rather small (I know that this open boundary has to reach the coast so that may not be always possible but well...). In version 6.2 you will have also the Thompson boundary conditions to help you.

With best regards,

Jean-Michel Hervouet

Hello,

Thank you very much for your hints, sir. I think I understand more.
Recently I have been reading your book: "Hydrodynamics of free surface flow: modelling with finite element method", which is quite good for students like me. But there's still something puzzling. Plate 16: Malpasset test case, whose open boundary is quite irregular(geometry), I don't know why this kind of open boundary is prefered.
So I wonder if you are so kind to further elaborate how this open B.C. is defined... dose it have anything to do with local bathymetry?

Best regard!

For the malpasset case, the open boundary condition (mediterranean sea) is a constant level.
Regards

Hello,

Sorry for my unclear presentation. I don't mean the open boundary condition, but the geometry pattern of the open boundary in Malpasset case.

Best regards.

Hello,

It is even a closed boundary.

JMH