open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello everyone

I am making a tidal prediction model for the Belgian coastal zone. To accomplish accurate results in this zone a continental shelf model is put up in Telemac. After constructing the grid and trying to run the model i have encountered a serious problem:

The model starts calculating but after a few time steps the velocities and water levels rise to impossible values in the order of 10^50. I have checked my grid and there is nothing wrong, no edge spanning elements or over constrained elements and only 1.5 % of the elements has an angle larger than 90°.

I have tried the following things to search for the cause of the problem:

- Instead of using tpxo and tidal predictions just putting a water level at the boundary which varies between -1 m and + 1 m.
- Making a grid with a uniform bathymetry of - 100 m.
- Changing the coördinate system from lat/lon to cartesian
- Using the TPXO Satellite initial condition

Non of the above worked so I'm starting to get hopeless :). The .cas file is in the attachment. I cannot send you the grid file but I can show a screen shot of it.

The grid is created in lat/lon and the bathymetry is in negative meters. Every bay has enough nodes so water entrance is possible. The smallest cells are about 800 meters wide so I chose a timestep of a minute to be absolutely sure the courant number stays very low.






I hope someone can help me here, thank you in advance!

Greetings

Tim

Hello,

If your mesh is in degrees, you need to create a grid in x and y co-ordinates following section II.2.9 of the principle note.

Hope this helps.

Sébastien (on behalf of Alan)

PS: a model of this size seems a bit extreme just to model the Belgium coast (?)

Thank you for the quick response I will try that and let you know. Yes it is a big model but we are going to use it for other projects in Europe and refine locally where we want :)

Hello,

Could you reply with a link to the document you are talking about? I can't find it on the website.

Thank you!