How to control the mesh quality of mesh adaptation?

- July 26, 2021 at 9:30 pm
  
  ZX
  Subscriber
  
  Hi, I am using VOF to do a simulation for 3D droplet formation, to capture the interface between the water and air, I used the mesh adaptation, like the figure shown below:
- July 27, 2021 at 8:51 am
  
  Rob
  Forum Moderator
  
  Is that a tet or poly mesh? If it's the latter try the same settings on the former.
- August 14, 2021 at 6:47 pm
  
  ZX
  Subscriber
  
  Hi Rob, thank you for your reply. After see your reply, I was trying all the time, but it seems still have problems.
  First of all, I use tet mesh. I found that if I used "Dynamic Mesh (including smoothing and remeshing) + Mesh adaptation", it always shows 'courant number is larger than 250' after hundreds of time steps. However, if I use: "Inlet velocity (or inlet pressure) + Mesh adaptation", rather than "Dynamic Mesh + Mesh adaptation", there is no error.
  In this way, could you please tell me if it is difficult to use the "Dynamic Mesh + Mesh adaptation"?
  Thank you.
- August 16, 2021 at 8:50 am
  
  Rob
  Forum Moderator
  
  Dynamic mesh is for remeshing and is used for moving bodies. The smoothing/remeshing etc are to remesh the domain to account for boundaries not being where they were when you created the original mesh. Depending on what settings you used it can very quickly turn a mesh inside out.
  Dynamic (mesh) adaption is to refine and coarsen automatically. In your model this is the approach I'd use.
- August 18, 2021 at 8:34 pm
  
  ZX
  Subscriber
  
  Hi, Rob, thank you very much for your reply. :)
  Sorry I should explain my model more clearly. The meaning of "Dynamic mesh+ mesh adaptation" is shown in the figure below, and for this application, there is always error "courant number is larger than 250" after hundreds of time steps. In this way, I am thinking is it difficult for Fluent to combine "Dynamic mesh" and "mesh adaptation"? I watched a lot of movies about "mesh adaptation", but none of them combines "Dynamic mesh".
  Thank you.
- August 19, 2021 at 10:41 am
  
  Rob
  Forum Moderator
  
  Dynamic mesh is something I don't use much, may be able to comment. I suspect you're moving something too quickly given the mesh resolution and the solver is then twisting the cells.
- August 19, 2021 at 4:16 pm
  
  ZX
  Subscriber
  
  Thank you!
- August 31, 2021 at 1:52 pm
  
  Stephen Orlando
  Ansys Employee
  
  I think combining Dynamic Mesh and Adaption should be fine. As Rob suggested, it could be the timestep is too large (mesh is moving too quickly). Maybe try lowering the timestep. Also, you could take a look at this VOF droplet tutorial, https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v212/en/flu_tg/flu_tg_vof.html?q=droplet