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  • August 17, 2017 at 5:20 am #6587
    samreen
    Participant

    Hi,

    I have created 2d area to model canyon. The length of canyon is about 4 miles long for which mesh is created. When I use 1 minute or more time step for simulation, then there was water only on upstream small section of mesh and did not cover up to downstream boundary. If I decrease the time steps for simulation less than 1 minutes like 1 second then, I could see water in whole length of mesh but it took more time, more than 24 hours. Also, the result doesn’t look reasonable. I mean water depth is higher (around 15 to 20 feet) for the width of 300 to 400 feet wide section even for small discharge (100 ft). I tried using different flows for different simulation time and also checked the Manning’s value. What might be reason behind these problems? Anybody please help me.

    Thank you

    August 17, 2017 at 11:04 pm #10818
    cameron
    Participant

    You should follow the courant criteria for timestep. You should also think about using the full momentum equation if you are not. Not sure of the grid cell size you are using, but that may also have an impact.

    August 18, 2017 at 5:25 am #10819
    samreen
    Participant

    Thank you Cameron for the reply. I will check courant criteria as well as try once with full momentum equation.
    Since, I am modeling for small canyon I used smaller grid cell size (4 feet). And the resolution of terrain is 1 feet. Does it have any relation with simulation?

    August 20, 2017 at 6:19 am #10820
    cameron
    Participant

    The smaller the grid cell the smaller the time step. With that small of a grid cell, your time step will need to be 1 second or less most likely.

    August 20, 2017 at 7:56 am #10821
    samreen
    Participant

    For the smaller time step (less than 1 sec), results look reasonable. I tried using full momentum equation but I got an error saying “Error with program: RasUnsteady64.exe Exit Code = -1073741819”. Then, I ran the model both by increasing and decreasing the size of mesh. I got the same error. Could you please tell me what might be the reason behind this error?

    Thank you

    August 20, 2017 at 8:27 pm #10822
    cameron
    Participant

    Hard to say what the error is as that is generic. Does it crash right away or after running for a little bit.

    August 20, 2017 at 11:48 pm #10823
    samreen
    Participant

    It did not crash. It showed the error and model was stopped.

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