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I'm trying to model a weir in the middle of a watercourse. According to the documentation and the various examples I've found, I've made a hole in my mesh so that the upstream and downstream sides of my weir are considered as boundaries. These boundaries are defined as "free velocity". What's more, my weir file seems to correspond perfectly to the model and the software recognises the weir because it displays 'Weir number = 1' when it is launched.
However, my model doesn't run well. The weir doesn't seem to be taken into account: the flow bypasses the weir and the model is unstable.
Can you help me find the cause of my problem?

You can find my simulation files at the following address: we.tl/t-RrTclQTGUQ

Thank you very much and have a good day :)

Hi
Read carefully the various manuals available...
The boundaries on weirs should not be declared as liquid boundaries but as solid boundaries...
In your case the free velocity BC win on the weir management condition...

Regards

I made a mistake sorry, in my boundary conditions file, this boundaries are clearly marked 2 2 2. I said that because it was it is written on Fudaa "Free Velocity" (you can have a look on the screenshot). But I have read the manual many times and all the conditions are met, that's why I don't understand.

OK
Then could you illustrate why for you the weir is not take in account?

The flow bypasses the weir

Forum rules - How to post - Point 7 !!!

Sorry but I've attached all my computation files in the first post. I don't know what you need more. I've joined the output .txt file juste here. Don't hesitate to tell me what you want exactly.

Usually files are attached in the message, not in a transfert system, except if size is too big...
By the way:
Wrong initial condition leads to oscilations which will take time to be damped
Weir crest level few centimeters upper than the upstream bottom level and even under the bottom level at ones node!
Bottom level on the left side of the weir under le level of the weir then flow could occur ...
Using variable time-step to achieve simulation is a bad idea. Understanding what goes wrong with the simulation by looking at the result at each time step is better...

Regards

Thank you for your advice.
I tried to :
- Put only water on the river bed for initial condition
- Have exactly the same upstream bottom level than the weir crest level
- Increase the bottom level on the left side
- Use a constant time-step
None of these modifications change the fact that the weir doesn't work well.

By conception, a weir is a vertical obstacle to the flow... Why using a weir if the crest level is at the level of the bottom?