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.

  • 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.

  • Hello Cesar,

    I've reviewed your model setup with and without rotated nested grids. 

    You have set time step that is largely beyond the recommended. Please follow the guidelines on how to setup the model time step with the MOHID Water engine

    Regarding the model becoming unstable with rotated grids, have you completed a full simulation of the father model before nesting the submodel? I'd like to call for your attention to: 

    1) the submodel temperature and salinity initial condition is different from the father model initial condition. 

    2) You are using 10 sigma vertical layers in a model with depths up to 1500 meters. No realistic initial and boundary condition was specified. Temperature and salinity have constant values which is not realistic. 

    3) Along the nested boundary domain, there are grid cells that can't access information from the "father" domain, because the "father" domain cells are land and the nested domain are water, due to the increase in resolution. I would recommend that you first run the model in 2D (1 vertical layer sigma) with the father and nested models. If the results are stable then, we can look at how to improve on to the 3D model. 

    I will wait for your reply. Thanks and regards,

    Luis

  • Dear Luis,

    Thank for your reply.

    I agree with everything you say. The truth is, a high DT and low horizontal resolution was configured to make the tests faster.
    Yes, I first run the parent model before doing the nesting. I am aware of what you point out in points 1 and 2.

    The reason for my insistence, is that under the same configuration the model with grids without rotation runs and finishes the simulation, instead, as soon as I assume even one degree of rotation the model does not start, it just blows up at once. I will check again that all open boundaries of my child model are within the water domain of the parent. 

    Finally, to avoid the irregularities and complexities of the coastlines, I have done the offshore test, where the grid of the child is completely inside the parent, but the simulation still does not start. 

    I will run the test you suggest and then let you know the results.

    Thanks for your kind attention.

    Cesar.

  • Hello Cesar,

    Could you please share the offshore model? Then I can track down what's happening. 

    Thank you very much and kind regards,
    Luis