This topic contains 2 replies, has 2 voices, and was last updated by Sr Shen sr Shen 1 week, 6 days ago.

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  • #5830
    Sr Shen
    sr Shen
    Participant

    Dear EFDC team users:
    During the simulation ,the model suddenly had negative depth.By the picture of velocity,we can see that in date 126, the water flows from 1 point to 3 directions,and then the depth changed from 3.49m to -0.0006m,so the simulation ended.I tried to change the boundary conditions and intial conditions but it didn’t work.Is it related with the shape of the cell? Or other factors? I really wana how to solve this problem.

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    #5835
    Tom Mathis
    Tom Mathis
    Moderator

    Hi sr Shen,

    Negative depth errors are almost always a function of the model timestep. Try with a more conservative (smaller) safety factor, and maybe a smaller initial timestep to see if that addresses the issue.

    Additionally, the problem may not be isolated to this cell alone. Using the 2-D plan view, view the Water Surface Elevation with the color ramp autoscaled by the view. Using this perspective, you can look around your model domain in the snapshots preceding the negative depth error crash and see if there is a “checkerboard” pattern in your water surface elevation anywhere. If you do see this, it is a telltale sign that your model is unstable. While the model may still continue running while it is unstable, the ultimate result could be a negative depth problem like the one you are seeing.

    Hope that is helpful to you!

    Tom

    #5841
    Sr Shen
    sr Shen
    Participant

    Thank you for your advice! The negative depth is related to the time steps.In addition, I found that it was also related to the characteristics of cells . Now I solved it and the model runs well.

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