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Hello,

I made a hydraulics model which gave good result of velocity field in the river. But the free surface seems quite strange. The surface elevation near the wall boundary is much higher than the rest of the domain.





It's not logical because the water should not behave like this way.
Why did this happen and does anyone know how to fix this problem?

Thank you very much!

Hello,

This is not a problem. The free surface is the sum of bottom + depth, so in dry zones it is the bottom elevation, thus post processors will always show you such things. Only Telemac has a specific algorithm to know that near to dry zones the free surface gradient is not the bottom elevation gradient. What you can visualize is the depth, with a threshold value of let's say 5 cm, you will see where the water really is.

With best regards,

Jean-Michel Hervouet

Hello,

I am just thinking: if you have vertical walls, you should not have the bottom elevation going up the wall, the bottom should remain flat (for example) and the depth large enough, till the boundary, and you need not include the banks in the domain. For example a bridge pier on a flat bottom: the bridge is like an island and the bottom remains flat. I have seen once a user that included the pier as a high elevation dry zone and this is absolutely not a thing to do.

With best regards,

Jean-Michel Hervouet

Thanks for your explanation. In the model, we have high slope gradient near the wall but it's not entirely a vertical wall. And those harbors in the domain were added in order to let the program generate more realistic flow patterns.



I also run the same case in Telemac-3D and I got velocities on the wall. Is it due to the same reason?

Yes, it is the same thing in Telemac-3D, and you may find velocities on walls due to influence of nearby wet points, however friction becomes infinite on dry zones and this should cancel velocities.

JMH