User Forum of Software BASEMENT

Dominik

User

From: Bern

Registered: 2018-09-26

Posts: 19

WARNING -> The velocity 'v=200.002 m/s' ... exeeed the max velocity

Hey,

I'm trying to implement different elevation data into a previous model. The model worked earlier with "old" elevation data. After adding the new elevation data to the mesh nodes I keep getting warning messages such as the one bellow.

WARNING -> The velocity 'v= 200.004 m/s' in the element # 212 exceeded the maximum
   velocity 'vmax=200 m/s' and is set to this maximum. No more messages are
   shown.

After the warning shows up, the outflow jumps to a negative value of more than -600m3/s and stays then negative. Boundary conditions are zero_gradient so that all water flows out of the area-of-interest.

The interesting thing is, that in some cases the change of height at one of the corresponding nodes helps but then the warning occures at a different element where it was not there prior.

Currently I'm struggling with an element called #212. What I tried so far:
-Changing the elevation to a rather flat area. Point (A) is 502.25 msl, (B) 502.27 msl and (C) 502.272 msl. Therefore, the slope should not be the problem.
-Angles at the corresponding nodes are: Alpa: 80°, Beta: 51° and Gamma 49° --> Don't thing the angles are too narrow.

Any ideas what could be the case for the warning?

Cheers
Dominik

Last edited by Dominik (2019-10-16 10:29:05)

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Dominik Vogt
MSc Student Institute of Geography University of Berne

Matthias Bürgler

Developer

From: Zürich

Registered: 2019-04-04

Posts: 150

Re: WARNING -> The velocity 'v=200.002 m/s' ... exeeed the max velocity

Hi Dominik

This error is typically related to the wetting/drying process of an element and cells with a large slope. Is element #212 a boundary element and what is the element area? Also what is your minimum water depth? You could try if a smaller or larger minimum water depth solves the problem.

Best regards
Matthias

Dominik

User

From: Bern

Registered: 2018-09-26

Posts: 19

Re: WARNING -> The velocity 'v=200.002 m/s' ... exeeed the max velocity

The minimum water depth is 0.02m. I can't tell you the exact size of that element anymore but it was between 1m2 and 100m2. The problem occured on various attempts in different simulations, always at different element #number. It didnt always occure at boundary conditions.
However, I changed the boundary conditions: A friend of mine suggested to use hqrelation with a slope of 10. This first looked promising but didnt work out either.
Right now I changed the boundary condition (at the outflow) to zhydrograph with an imaginary lake which has the wse of the terrain so that no backflow occures. This seems to work so far...
Thanks for the help though, Matthias!

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Dominik Vogt
MSc Student Institute of Geography University of Berne