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Hi,

I model a coastal area in regards to the morphologic evolution. At the moment I try to set up the model, but I'm facing some instabilities, which I can not really explain and solve.
I tried as classical boundaries conditions as well as Thompson, but that does not help. My time-step is at 1 sec so this should not be a problem either.
Attached are my model files. At the moment it just takes care about the tide but waves should be added later as well.

Thanks so much in advance for help.

Hi,

I'm not an expert, but I follow your case with great interest.

One thing I found is that your boundary condition is at 0.05m at time zero and your initial water elevation at 0.00m. This will shock the system and instabilities are introduced.

2nd I obtained a smooth solution by closing the east and west boundary (2 2 2). So you should look into the boundary condition to smooth your simulation.

Hope this helps you to understand the model.

Kind regards,
Patrick

Hi,

great to hear that.
I changed the boundary conditions so that initial water elevation and tide both start at 0.00 m.

Unfortunately I'm not totally sure what you mean with closing the boundary. Could you maybe help me and try to explain it with a picture?

As soon as the simulation is finished I will tell about more about the instabilities.

Best
- Clemens

When changing the initial condition and matching it to the boundary condition the instabilities are almost gone.

I assume the other instabilities are caused to the time-step. The only other issue I'm facing right now is the fact that I had to use other boundary conditions (attached), since it was not possible to run the model with the open sides.

Unfortunately does this closed wall cause some issues in the area of interest.

Hi Clements,

What I meant with closed wall is that I took out the east and west boundary. So I ran with only the south boundary. I think you did the same.

Good to hear you made a step in the right direction. I think smoother solution can be obtained with different schemes or damping, but I have no experience with that.

I hope someone else from the community will help you (and will learn more about TELEMAC!)

Patrick