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Weir overtopping using FEM in both T3D and T2D slope problem
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TOPIC: Weir overtopping using FEM in both T3D and T2D slope problem

Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35128

  • amanj2013
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For the past couple of days, I tried both T2D FE and T3D which I believe FE is the only choice as far as I know, and there is always instability on the downward slope you can see from the attached snapshots. I tried T2D FV and its stable but the WSE disagrees with the experimental DATA. I wanted to try non-hydrostatic version and I believe its the reason for the discrepancies between Numerical and Experimental. I tried Flow3D and the result is much better but still not in good agreement. Here I attached a cas file and hope someone can share an opinion or solution for this cASE. I also tried BOUSSINESQ and still unstable as I mentioned its only FE not FV for non-hydrostatic version.

FYI: the model run in v8p1 and also V8p0 and even earlier versions and same results.
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Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35145

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and here is the result of flow3D, T3D nonhyd and Hydr., and T2D-FV.

Still strong oscillations on water surface elevation!

Amanj
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Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35154

Dear Amanj,

I am surprise you obtained the same results in v8p0 and v8p1: default options are changed.

Could you try in v8p1 to add:
NUMBER OF CORRECTIONS OF DISTRIBUTIVE SCHEMES = 15

and remove:
OPTION FOR CHARACTERISTICS                               =2
FREE SURFACE GRADIENT COMPATIBILITY                      =0
SOLVER FOR DIFFUSION OF VELOCITIES                       =7
SOLVER FOR PROPAGATION                                   =2
MASS-LUMPING FOR VELOCITIES                              =0.5
SOLVER FOR PPE                                           =2

Best regards,
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Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35203

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Hello,

I have notices that in the T3D dic file that this option is omitted as can be seen from the screenshot.

I also tried similar case such as malpasset cas setting and the result is shown in the attached screencast. the cas file is also attached,

Moreover, I have noticed that during low flow depth at the beginning of simulation is smooth then turn instable and strong oscillations as flow depth increases and then flow decreases and turn to be smooth on the slope while on downstream mild slope strong instability.
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Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35204

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More pics

Pls note the solution times!

AMANJ
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Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35215

Dear Amanj,

Could you post the full setup of your case here?
Is there any difference if you reduce your time step? The output boundary condition is torrential?

I do not understand which option is omitted.

2 choices (v8p1) for more "robust" options:
1
SCHEME FOR ADVECTION OF VELOCITIES = 5 (default 5)
SCHEME OPTION FOR ADVECTION OF VELOCITIES = 4 or 2 if no dry zone (default 4)
NUMBER OF CORRECTIONS OF DISTRIBUTIVE SCHEMES = 15-20 (default 1)
NUMBER OF SUB-STEPS OF DISTRIBUTIVE SCHEMES = 10-15 (default 1)
2
SCHEME FOR ADVECTION OF VELOCITIES = 13 or 14 / 4 or 5 if no dry zone(default 5)
MAXIMUM NUMBER OF ITERATIONS FOR ADVECTION SCHEMES = 1000 (default 10)

J
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Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35217

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Hello,

Here is the case:
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Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35218

Dear Amanj,

Just to be sure:
Your test case looks like Balzano (in TELEMAC-2D). There is no inflow, free outlet (in contrary with Balzano where h is imposed at the outlet). And you expect at the end no water downstream the weir.
Am I true?

Best regards,
J
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Weir overtopping using FEM in both T3D and T2D slope problem 4 years 10 months ago #35225

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Hello,

I don't know about the Balzano and In just realized that exist. Yes my case is like what you described, even with inflow and continuous downstream flow and wet, still get the same instabilities. I tried with very small time steps and at some points crashed and not significant reduction in spikes!

AMANJ
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Weir overtopping using FEM in both T3D and T2D slope problem 3 years 9 months ago #37699

  • paatpau
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hello, do you know how to run the balzano test case ? iam new here and i dont understand what todo
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