open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello Peter,

I was able to run your simulation after a couple of changes (I didn't have spaces in my path).

It had a problem with you boundary condition, supercritical flow at the entrance.

This is what made it work ono my machine:
- create boundary file
- set PRESCRIBED FLOWRATES to 35.0;0. (no flow needed for downstream)
- set PRESCRIBED ELEVATIONS : 0.;154. (your bottom ranges from 148.6 to 154.8) so 371 is a bit high
- set INITIAL CONDITIONS : 'CONSTANT ELEVATION'
- set INITIAL ELEVATION : 154 (same as boundary condition)

Hope that helps,
Patrick

Thanks everyone! :)
And thanks Patrick, your changes make sense and now I can continue with my model!
Best regards
Peter

servus_superbus wrote:
Hello again guys!

I could successfully run some simulatios now and decided that my model is ready to calculate with the in-situ values.
I now changed the Initial elevation and the flow rate to the measured values.
When I run the simulation it shows some issue: CVTRVF_NERD_2 (SCHEME NERD, 13 OR 14): 50 ITERATIONS = MAXIMUM
Should I change the number of maximum iterations? In the forum I read that this is rarely a solution. Or is there another flaw in my .cas file that results in this message?
The input files are attached, the geometry file is zipped.
Thank you in advance!
regards
Peter

Hi Peter,

I just looked at your cas file and I'm pretty sure this is an initial condition and boundary issue.
If you start the model with a constant elevation, no velocities and fixed discharge at the upstream boundary you shock the model. You need to think about how to get to a stable flow in the model (using restart option/slowly increase inflow).
Second boundary conditions need water at all the points and no critical flow, that's why in the example I ran i put 154m at the boundary. if you want to work with 152m you might want to extent the model to ensure water at all nodes and no recirculation (inflow at the downstream boundary).

Hope that helps,

Patrick

Hi Patrick,

Ok I see, thank you! I need to reconstruct the measured conditions where the water surface elevation was at 152 and the inflow was about 18-19m^3/s. So I should modify the inflow/ outflow area so that all of it is covered by some water? Or what exactly do you mean by extent the model?

Best regards
Peter

Hi Peter,

Yes, you should modify the in and outflow area. Depending on your area of interest you can modify the bathymetry in the mesh you have or add upstream/downstream sections to your mesh.

Patrick

Hi Patrick,

Sorry to bother you again but I don't understand what exactly I should modify.
I tried a decreased in-/outflow area (to no avail) but if I make it even smaller isn't it going to act like a funnel?
I also changed the boundary conditions to prescribed Q at inflow and to prescribed H at outflow, still I get the same log with maximum iterations.

My area of interest is the meandre. I can add cross sections upstream from it but how would that help?
"modify the bathymetry in the mesh ": so it might be a mesh issue after all?

I'd be very thankful for any help!
Peter