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Is it possible analysis low flow conditions of a river with Nays2Dflood

  • Oct 23 2019
  • c.niroshinie

I Analyzed the velocity fields and water level fluctuations of a river with Nays2dFlood. I used very fine geographic data of the river and results seems reasonable. However, I want to confirm is it appropriate to use Nays2Dflood for low flow conditions as well.

I can’t use Nays2DH, as I need to add the inflows from tributaries. That’s why I used Nays2Dflood.


  1. UC-1h says:

    If you are not satisfied with results for low flow conditions.
    I suggest that calculation grid size reduce smaller.

    • c.niroshinie says:

      Thank you very much for your suggestion.

    • says:

      I used Nays2Dflood and I use small grid size (W16000 dj12.5 nj1280 and ni4500 di 14) then the calculation was fail, so I would like to know how much smallest gird size we can determine or limitation of grid size. thank you very much

  2. c.niroshinie says:

    How is the time step for calculation? You should change the time step for the calculation when you change the grid size.

    • says:

      I always use output time interval 600 second, calculate time step 0.2 second, i just follow the guideline but i do not know how to determine these time also, could you please clarify. thank you

  3. c.niroshinie says:

    dt (calculation time step) should be given to satisfy CFL condition.
    It should be the minimum of dt < dx / { [u] + (gh)^1/2 } and dt < dy / { [v] + (gh)^1/2 }

    you can reduce your time step to 0.1 or 0.05 and see. How about the inflow and the water depths?
    If you send your model I will check the mistake.


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