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Preprocessing

Topics relate to geometry, meshing, and CAD

Prism bad orthogonal quality.

    • Piotr Kluba
      Subscriber

      I am trying to create a mesh of a formula student vechicle with 15 layers of inflation layers in FLUENT Meshing. Independently of the type of mesh that i am using the prisms that are created have a bad orthogonal quality - this happens only when there is a sharp angle in the geometry (~ 90 degrees) or where the mesh transitions between the regions of different first layer thicknesses. All of the zones have the same amount of layers and I am using the last ratio method. I tried meshing and then using auto node move but with no success. I am attaching the screenshot of the geometry and the bad prisms. Is there another way of fixing this other than rounding every corner i have in the model?

      My surface mesh quality was perfect (skewness < 0.5). Any advice would be really appreciated!

    • Keyur Kanade
      Ansys Employee
      The min orthogonal quality should be above 0.1 to proceed to solver. If it is less than 0.1 then please improve the mesh. 
       
      Please try to use same number of layers on all surfaces. If you use different layers then it will introduce pyramids and will result in bad quality. Please increase first cell height. 
      Please go through help manual for more details 
    • Piotr Kluba
      Subscriber

      I know that the quality is bad, that is why i want to improve it. I am using the same amount of layers everywhere, I eliminated stairstepping completely. I do not want to increase the first cell height because it will not provide me with a wanted y+ value later in the simulation. I also already have read through the manual and it unfortunately did not help much :(.

      Regards,

      Piotr

    • Keyur Kanade
      Ansys Employee

      If first cell height can not be increased then please refine surface mesh further. 

      Regards,

      Keyur

      How to access Ansys Online Help Document

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      Fluids Engineering Courses | Ansys Innovation Courses

       

    • Piotr Kluba
      Subscriber

      So there are no methods of keeping the quality high while having a coarse surface mesh and a low first layer height?

      Regards,

      Piotr

    • Keyur Kanade
      Ansys Employee

      Please check orthogonal quality defintion in document. As you coarsen the mesh and lower height the mesh quality reduces. Please make sure you are using appropriate first height and not using very low first height. 

      Regards,

      Keyur

      How to access Ansys Online Help Document

      Guidelines on the Student Community

      Fluids Engineering Courses | Ansys Innovation Courses

       

    • Piotr Kluba
      Subscriber

      I tried refining the mesh and enlargeing the first layer, but the problem is still significant.

       

    • Keyur Kanade
      Ansys Employee

      What is min orthogonal quality of your volume mesh? 

      What is surface mesh size you are using? What is first hegiht of prism? 

      Regards,

      Keyur

      How to access Ansys Online Help Document

      Guidelines on the Student Community

      Fluids Engineering Courses | Ansys Innovation Courses

       

    • Piotr Kluba
      Subscriber

      So, after a lot of iterations of auto-node-move i managed to bring the quality up to 0.043514615. When it comes to the surface mesh size, on the problematic areas the cells have the size of around 5, but there are areas where the face size is near 3 and the problem persists. For the first cell height i have for different zones from 0.01 to 0.08.

      Regards,

      Piotr

    • Keyur Kanade
      Ansys Employee

      Ideally min orthogonal quality should be 0.1. But practically 0.04 can work. 

      Regards,

      Keyur

      How to access Ansys Online Help Document

      Guidelines on the Student Community

      Fluids Engineering Courses | Ansys Innovation Courses

       

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