Learning Forum

[Alberto]

Goomorning,

I'm trying (without success) to do a dynamic mesh simulation over a falling 3D object (with a particular complex shape). What i want to try now, to avoid negative mesh volume error, is to bound the object with a sphere (enclosure) which follow its motion. 

My question is: I have to subtract this sphere from the bigger domain? or i have to subtract my object to this sphere too? How can i manage with boolean? I have no idea. I know about 6dof option  passive, and i will use on the sphere, but before i have to do some boolean operation? How cna i proceed in this way?

[Federico Alzamora Previtali]

What you are describing sounds like Overset meshing, where a component mesh will overlap and move through a background mesh. In that case, you will mesh the background and component mesh independently (with overlap), and append each to your Fluent case. Ideally, you would create both domains at the CAD level using Discovery or SpaceClaim.

Regarding Negative volume error, this error results from excessive cell skewness due to excessive boundary motion. Make sure that your time step is small enough to avoid any boundary zone movement to go beyond 1 cell at each time step. If you're using Remeshing and/or Smoothing, make sure your settings are set correctly for your mesh distribution.

[Alberto]

I want to use dynamic mesh. I've created this inner enclosures in order to keep mesh near the body more regular. I did a good mesh, i have orthogonal quality minimal value = 0.15 and maximum aspect ratio = 13, minimum skewness is about 1e-4.