open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi !
I'm looking for some advices from the Telemac community.

I'm focus on the 2d hydrodynamic on the Seine bay sector. I'm using tpxo for my boundary conditions imposing sea elevation and velocity. My mesh is in attachment.
My problem comes from the sea level signal. In attachment as you can see, I have extracted the sea level for my 3 reference stations, and I have instabilities during low tide.

I have extracted the sea level close to my two tpxo boundaries (Atlantic side and North Sea side, the locations are given by the two red point on my mesh). As you can see, the Atlantic boundary side have a lot of instability. i have applied the Thomson option, check the solver and anothers parameters, but I cannot succeed to reduce the instability.

Do you have some advices ?

Thx a lot

Regards,

Hello,

My first advice is to try other tidal solutions coming from the Oregon State University, like the Atlantic Ocean regional solution or better the European Shelf local solution: people.oregonstate.edu/~erofeevs/

What about your time step and solving steps? Are there many iterations or just a few? What about the size of your mesh elements? And the Froude number during the simulation? Have you tried decreasing it?

You can decrease some spurious oscillations by decreasing the value of the keyword FREE SURFACE GRADIENT COMPATIBILITY, from 0.9 to 0.5 e.g. or even 0. if it helps you.

Perhaps increasing the number of smoothings of the bottom may help you as your issue only occurs during low tides.

At last, you can change TREATMENT OF NEGATIVE DEPTHS from 1 to 2.

Hope this helps,

Chi-Tuan

Hi Pham,
thx you for your time.

After several tests, i have changed the txpo boundary to a regional solution.
the oscillations were still there but after deactivate the thomson option, the results are good.
It not the first time that the Thomson option creates this kinds of oscillations.

Anyway thx Pham !

Hello,

Good news if you have solved your issue. You are right, I also experienced spurious oscillations with Thompson boundary conditions sometimes.

Chi-Tuan