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Hi everyone

I'm running a file and it suddenly closes Qs bedload outlet (attached image, step 397).

It must be considered that the flow is supercritical, I attach the input and output files (sorry for the small value of "GRAPHIC PRINTOUT PERIOD" but wanted to know the exact point where the closing occurred.

drive.google.com/file/d/0B3SO9sCBMyDMOFR...V3M/view?usp=sharing

You can even see, the flow of liquid entering the outlet

Hello,
This is very strange indeed. Are you sure that your hydrodynamics conditions didn't change during your simulation ?

pablo

Hi Pablo

Yes, there were no problems, the preprogram files are the only hydrodynamic files.

For now, I may solve the problem by placing downstream condition, however, in theory I should not need it.

Thank

The issue is caused by your flow boundary conditions, using 5 5 5 at the entrance and 4 4 4 on the exit boundary, which is numerically unstable. Change it to 4 5 5 on the entrance and 5 4 4 on the exit, that should sort it.

Michiel

Hi michiel

I have supercritical flow conditions, so I use those limits.

Thanks

I missed the point about the supercritical flow. However, the current boundary conditions are under-prescribed and allow for the result you are getting.
The model is creating an hydraulic jump with the free surface elevation on the outflow boundary rapidly increasing. That means the flow velocity drops of to zero giving no sediment transport. Then the model reverses the flow at the downstream end (nothing in your setting prohibiting this). In the end you get an instability at the upstream end.

Would it help leaving the upstream BC in the cli-file as it is, but change the outflow BC to 5 4 4, fixing the water level there at 0.03, or is that too restrictive.

Yes, that did and it works, but I do not think it's the best solution.

Thanks