Unreasonably high WSEs in 2D

[jfeuerstein]

Hello,

I’m trying to run a 2D 100-year flood event for an existing conditions model to compare to the existing 1D model. The inflow hydrograph I’m using ramps up from 0 to 20,170 cfs over 48 hours where it remains constant for 48 hours before ramping back down to 0. I figured this would give me ample time for the model to begin running, get up to speed, and give me consistent results. Unfortunately, I am getting illogical results, WSEs 100s to 1000s of feet higher than my terrain, and the water moves in waves, before disappearing and restarting. I’ve tried changing lengths of US and DS boundary conditions, Manning’s n, adding breaklines, but the issues continue.. Has anyone had similar issues before? Any advice on how to fix this? Thank you

[cameron]

probably a time step issue. Run the model with the full momentum solver and use dynamic time steps that are controlled by the courant number.

[jfeuerstein]

Thank you, I think it was an issue with using diffusion wave and having too large of time steps. Now I begin to have reasonable results, but RAS goes unstable and gives me this error:

Error with program: RasUnsteady64.exe Exit Code = -1073741819

Any idea how to solve this?

[cameron]

The code doesn’t help.

The program is usually pretty stable as long as the time step is reasonable for an all 2D model. Do you have any culverts or other hydraulic structures in your 2D model?

If you are getting a lot of iteration error messages when running it in full momentum, I would check to see where those are occurring and adjust the cells.

Not sure what time step you are using or your cell size but try going smaller on the time step.

[mistral]

Are you using dynamic time step? I had a similar failure and it helped to lower the minimum courant number.

[Author]

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