Using overset mesh in 3D with symmetry plane

- May 7, 2019 at 11:52 pm
  
  Extremepeta
  Subscriber
  
  Hello,
  
  I have a question regarding using overset interfaces along with an axi-symmetric domain in 3D. I am trying to simulate a rectangular box floating on water. When I create the overset interface between the fluid domain and overset component, I end up with orphan cells around where the overset component is cut in half by the domain symmetry plane. It makes sense since it needs 4 cells between boundaries to create a good overset. My question is how do I (or can I) use overset interfaces with a symmetric boundary condition?
  
  The yellow cells are the symmetry boundary condition for the fluid domain; the grey ones are the box that I am trying to analyze, and the red cells are the orphan cells. Other details are that I am using Fluent with ANSYS R19.2 and am using the student version. I know the elements are coarse but I am trying to compare half-model results with that of the full model. Full model is running close to the element limit and I want to keep the element size between the full and half models the same for comparison.
  
  Any help would be greatly appreciated!
  
  Peter
  
  Edit 1: Embedded picture of mesh and orphan cells.
- May 8, 2019 at 9:45 am
  
  Rob
  Forum Moderator
  
  Assuming the overset block is flush to the symmetry plane try setting the overset block surface to symmetry too. I don't think you can have solid zones in the overset mesh either, it's got to be a void.
- May 8, 2019 at 1:35 pm
  
  Extremepeta
  Subscriber
  
  Yup, you are right. I didn't have the block perfectly flush with the symmetry plane. I made the block flush with the symmetry plane and added a symmetry boundary to the overset compenent and it intersected successfully with no orphan cells. As for the solid zone, I did use a void in the middle of it, I apologize if that was not clear in the initial problem statement. But yes, I used a void for the box I was analyzing and set those boundaries as walls so I could get force reports on it during the simulation.
  
  After some more searching, the Fluent manual states in the Overset Topologies section that physical boundaries cannot intersect each other. Only overset boundaries can intersect physical boundaries or other overset boundaries. Physical boundaries are allowed to overlap (i.e. being coincident) as long as they do not overlap.
  
  Thanks for all your help!
  
  - Peter