Problem using grids with angle in nested models?

Dear OF community,

I have a situation with model nesting, which I would like to put under your analysis. When I run two nested domains with grids with an angle of rotation, the model just blows up. Under the same configuration but with nested grids without angle, the model usually runs fine.
Would it be possible for you to take a look at my model and give me feedback?  
How do I attach the folder of my model? I understand it is select Insert > Insert Image/Video File in the editor toolbar, but I don't see the way to attach.
Best regards,
César.

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  • Hello Cesar, 

    Sure, please upload your workspace. Here you can read about Sharing Hydraulic Model Files on the OpenFlows Forum.

    You can export an OpenFlows FLOOD workspace as explained here

    Kind regards,
    Luis

  • Hello Luis,

    Thanks for your kind reply. I was finally able to upload the files (option 2). The file name is "Coastal_lagoon-Nested.ows".
    In the Tide module, the tidal harmonic components for the parent domain with rotation are set to off. The other harmonic components are for the domain without rotation.
    I leave the file names of the grids:


    Name of grids without rotation:

    Bati-Dad_400
    Bati-Son_400

    Name of meshes with rotation :

    Bati-Dad_400_Ang
    Bati-Son_400_Ang

    Thank you for your support!

    Regards,

    Cesar.

  • Dear Luis, thank you for your reply.

    About the tide, it is because I am still working with an old version of FES (for some reason it does not download the FES2014 from the page you shared). Indeed, as I get closer to the coast, the generation of the tidal components starts to fail.

    Luis, the model with the grids without rotation is set up like this, to show that even when I am close to the coastline and the cells starts to become more irregular between domains (parent/child), my nested models run.
    Now, you have told me to test with a single sigma layer (2D). Well, the models with the grid without rotation run fine. The models with rotation don't even start. The latter, do not have river discharges because I want to avoid the argument that there are cells of the child that are above land in the parent. So, all child domain is inside the parent domain.

    Even with this basic configuration, can you please do the runs and confirm that the models without rotation run well, and that the models with rotation, even though the configuration is basically identical to the model without rotation, do not run?

    thank you very much,

    Cesar

  • Hello Cesar,

    I've used your rotated grids and FES2004 tide files and created a new project. I've started with only one layer and tide forcing and the model runs fine. Then I've added 10 sigma layers (thickness = 0.1) and everything is OK. I'll try adding the atmospheric forcing and temperature/salinity and will get back to you as soon as I've got an indication of what the problem is. 

    Thanks and regards,
    Luis

  • Dear Luis,

    thank for your usual kindness and support.
    I will be attentive to any findings and indications from you.

    Best regards,
    Cesar.

  • Hello Cesar,

    Apologies for taking long to find a solution.

    Indeed there is an issue when using rotated grids. The problem is related with the way FLOOD writes the nested grid file. When you create the nested grid, the format is written as if it was a curvilinear grid (even know it's not). However, when your parent model is rotated, your nested grid must have the same orientation. The MOHID Water engine gets "confused" when the nested grid "suddendly" is assumed curvilinear, thus the error. 

    There is a solution for that. You must open your nested bathymetry file and erase the <CornersXY>/<\CornersXY> block and then write the following keywords:


    CONSTANT_SPACING_X : 1
    CONSTANT_SPACING_Y : 1
    DX                                      : 0.004
    DY                                      : 0.004

    Make sure you change the grid angle in the nested grid from zero to 12

    GRID_ANGLE                    : 12

    Keep in mind that these values are specific for this simulation. Another set of nested grids the values would have to be changed accordingly. You only need to do 

    Please let me know if this works. 

    Kind regards,
    Luis

  • Dear Luis,
    thank for your support. Indeed, with that modification in the nested bathymetry the model now runs.

    Best regards,

    César.

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