Big Growth Ratio has more elements and nodes number than low Growth Ratio

- June 5, 2023 at 4:13 pm
  
  MUHAMMAD AMIRUL HUSSEINI JOHAN
  Subscriber
  
  Hi, I'm new to Ansys and currently building a simulation about jet fire modelling. I have create a 3D geometry with 1.2 growth ratio. Then, I duplicated the same 3D geometry and changed its growth ratio to 1.5. However, I discovered the number of elements and nodes for 1.5 GR is bigger than 1.2 GR, which is supposedly smaller. Can anyone help me with this
- June 6, 2023 at 2:00 pm
  
  Rob
  Forum Moderator
  
  How many cell zones are there, and did you mesh in the same order both times? I agree that the larger growth rate should produce a lower cell count, but there are other factors to consider.
  - June 6, 2023 at 3:15 pm
    
    MUHAMMAD AMIRUL HUSSEINI JOHAN
    Subscriber
    
    I think there are 2 cell zones which is an inlet and solid wall, and yes, I did the same mesh order by duplicate the first system (GR 1.2)
    - June 6, 2023 at 3:25 pm
      
      MUHAMMAD AMIRUL HUSSEINI JOHAN
      Subscriber
      
      For your reference, picture above is the mesh with GR 1.2
      And this is the mesh with GR 1.5
- June 6, 2023 at 4:06 pm
  
  Rob
  Forum Moderator
  
  You're limited by the free mesh type. As it's structured the growth rate may not allow the size change to occur. I'd not be happy with the results off either mesh.
  - June 6, 2023 at 5:09 pm
    
    MUHAMMAD AMIRUL HUSSEINI JOHAN
    Subscriber
    
    Could you please provide me with some suggestions for improvement? I would appreciate it if you could give me some suggestions on how to improve.
    - June 6, 2023 at 5:20 pm
      
      MUHAMMAD AMIRUL HUSSEINI JOHAN
      Subscriber
      
      Is it the free mesh type option that I need to change?
- June 7, 2023 at 8:38 am
  
  Rob
  Forum Moderator
  
  You have a few options, but they may be solver dependent. Why are you avoiding free mesh and wanting hex?
  - June 7, 2023 at 3:06 pm
    
    MUHAMMAD AMIRUL HUSSEINI JOHAN
    Subscriber
    
    I'm avoiding free mesh because it will create irregular meshes. I'm wanting hex mesh because it is in my project requirement.
    This is the mesh generated when I chose "Hexa Dominant" in the Free Mesh Type
    This is the mesh generated when I chose "Hexa Core" in the Free Mesh Type
- June 7, 2023 at 3:27 pm
  
  Rob
  Forum Moderator
  
  Hexa dominant is for Mechanical, it was never intended for CFD, and produces awful levels of skew. It's not supposed to work when CFD is selected in the meshing section but "free cell" may overwrite that setting.
  If you want a pure hex mesh with good uniformity turn off inflation and see how that goes. You may need to decompose the domain further to get the mesh you want. We used to do this routinely, now we tend to use a mix of hex & tet with inflation or poly & inflation.