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Hello everyone,

I'd need your help to solve a problem with the boundary condition.
I have a mesh with about 90m side of the triangle.
I have 6 open boundaries: 1 is the outlet boundary and the others 5 are the inlet boundaries.
When I run a simulation with TELEMAC2D it starts and goes on until a certain time step (lets say after 100 time steps).
At a certain instant one boundary condition (Boundary condition n°4) becomes dry and TELEMAC stops the calculations.
I extracted the results until the time step before it stops, so time step 99 and this is the result: the boundary at the beginning is wet and then it start to be dry.

I've tried to change the inlet discharge with the following results:
if I increase the inlet discharge the simulation stops before time step 100.
if I decrease the inlet discharge the simulation stops after time step 100.

In the attachments you can find some screenshots of the simulation from time step2 until time step 99 (the one before the simulation stops). As you can see in Figure "timestep99" the velocity assume a very high value in proximity of the boundary (about 60m/s).

I attach other files that can make easier to understand the problem.

Do you have any suggestion?


Thank you in advance,

Daniele

Your liquid boundary becomes dry because the flow is probably torrential.
If so, you should impose the discharge and the water level or change your mesh locally to ensure a subcitical flow on the boundary (you could add a small piece of flat channel upstream thios boundary for exemple)

Regards

Thanks a lot!
I've tried with the solution of flat channel and the simulation goes on but later it stops again.
I'm trying to impose a discharge and water level but I have some doubts about the liquid file. I attach a copy of the liquid file of my simulation. I'm quite sure that it is not written correctly.
Could someone please check it??

Thanks in advance,

Daniele

I would check the followings:
1 bathymetry: not sure the exact range of your bathymetry. The water level boundary seems really low comparing with your bathymetry surface

2 I would try to use 'Constant Depth', instead of 'Constant Elevation' since your surface has significant elevation drop

3 For your liquid file, I am guessing rank #2 is the outlet. If you are imposing constant elevation through your simulation duration, you can set the value (e.g. 206) in the case file, and do not need to set it in the liquid file

Let me know whether these work

Hailiang

If rank #2 is your outlet boundary, you only need to include flows for the other ranks (1, 3, 4, 5, 6). I think the liquid file in your first post has the correct formatting except you do not have to set the SL(2) since it is a constant