BASEMENTBasic Simulation Environment for computation of environmental flow and natural hazard simulationLaboratory of Hydraulics, Hydrology and Glaciology (VAW)ETH Zurich | ![]() |
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Hello,
I tried to do a hydraulic simulation in a large river. Horewer, I have a long list of mass balance problems at the first iteration. No problems appear for the next iterations and I can run the simulation until the end.
-> Progress: 0/100, dt = 0.02, RTS = 0
MASS BALANCE PROBLEM: h = -0.610542 < 0.0
MASS BALANCE PROBLEM: h = -0.573999 < 0.0
MASS BALANCE PROBLEM: h = -0.731428 < 0.0
MASS BALANCE PROBLEM: h = -0.791608 < 0.0
I set up an initial "dry" condition and I have two uniform_in boundary conditions.
What could be the problem ? Is it really a problem as I could run it until the end ?
Thanks for your hep in advance
Déborah
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Hi Déborah,
you can try starting the simulation with other conditions, such as "region_defined" (BM3.x) or index_table (BM2.8) with which you can set x and y velocities (u and v) and either the water depth (h) or water level (wse).
Dry initial conditions could give some warning, but if everything runs and you get reasonable results I would not be much concerned about the mass balance warning!
Cheers
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Hi Déborah
Are you using the safe_mode option in Hydraulics/Parameters with "off" or "on"?
Best regards
Matthias
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Hi
No I'm not using the safe_mode
Best regards,
Déborah
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Hi
I have played around with the initial conditions and minimum water depth: I had mass balance problems when I started from region defined conditions, I tried to use dry intial conditions and I got no problems.
So my answer is not completely correct, I am sorry.
However, I have to set the minimum water depth to a value larger than 1 cm (which makes perfectly sense), otherwise I got the mass balance problems.
Last edited by Matteo Facchini (2020-04-09 14:59:03)
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Still I cannot run the Flaz tutorial from the command line because of the mass balance problem, while it works if I run it from the GUI
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Hi Matteo,
Thank you for feedback.
I set up a minimal depth of 0,1m, but I still have the problem.
I didn't try to run from the command line.
I changed one boundary conditions, I still have mass problem balance at the beginning however the results seem to be quite good. Then I think I wouldn't take into consideration the mass problem balance.
Déborah
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Still I cannot run the Flaz tutorial from the command line because of the mass balance problem, while it works if I run it from the GUI
That's strange, I don't get a mass balance error regarding of CLI or GUI (omp with 7 cores, double). Which backend and precision are you using Matteo?
Regards
Matthias
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Hi Matthias,
I posted a complete reply here
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