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-   -   Using Volumetric Control as Part Input for Wake Refinement (https://www.cfd-online.com/Forums/star-ccm/242326-using-volumetric-control-part-input-wake-refinement.html)

fluid23 April 15, 2022 09:17

Using Volumetric Control as Part Input for Wake Refinement
 
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Does anyone have any ideas how I might go about using surfaces on a volumetric control body as the input surface for a wake refinement mesh operation? Long story short, I have a rotorcraft modeled using the blade element virtual disk. The downwash from the rotor needs some refinement, but I am only able to select surfaces which are boundaries in my domain as input part for surface mesh operations.

I want to be able to use the volumetric control I used to set the mesh inside the rotor momentum source as the input for the wake mesh.

My backup plan is to either create a CAD body or use field function refinement, but those are a little more involved than what I felt was necessary for this situation.

LuckyTran April 15, 2022 14:56

You can't use surfaces that don't exist.

I don't really follow how you use a volumetric control without a part. I would say create the part but shouldn't it already exist?

pi120 April 18, 2022 14:35

Hi, I have the same question. Please let me know if you find a solution
Thanks

cwl April 19, 2022 04:48

Quote:

Originally Posted by fluid23 (Post 826301)
The downwash from the rotor needs some refinement, but I am only able to select surfaces which are boundaries in my domain as input part for surface mesh operations.

Yep, that's correct - since surface controls can be applied only to surfaces where remesher does the job, i.e. surfaces that correspond to the region boundaries.

Quote:

Originally Posted by fluid23 (Post 826301)
I want to be able to use the volumetric control I used to set the mesh inside the rotor momentum source as the input for the

My backup plan is to either create a CAD body or use field function refinement, but those are a little more involved than what I felt was necessary for this situation.

If you have access to recent versions - you can use the adaptive mesh refinement, that looks like the best option.

Or - indeed extract field function containing target mesh size as a XYZ-table and remesh in simulation operations loop.

fluid23 April 20, 2022 11:44

LuckTran: I think I misspoke. What I meant was I wanted to be able to use the same part that I used for the volumetric control which I used to set the mesh size for the virtual disk momentum source. I have a part for the rotor disk, but it is not part of the surface mesh operation, only a body of influence used for a volumetric control. As CWL confirmed, a wake refinement surface control can only be applied to surfaces on a region boundary.

pi120: I have played around with various approaches, but never found an elegant solution. The best option I have found was to create a truncated conical CAD body and then create an additional volumetric control to set the mesh size in the region where the rotor wash was resulting in high TKE (and other issues).

CWL: Thanks for confirming my suspicion, which is actually pretty obvious if I just stop to think about it. Adaptive mesh is an interesting thought, but I think will have the same drawback that I foresee with field function refinement. Basically, the space that needs refinement has pockets of low/high TKE and turbulent viscosity. This could leave pockets of unrefined mesh which could pose a problem when I move this from steady state initialization to unsteady. Maybe I'm making a mountain out of a mole hill. I'll give it a shot if I have time.

Thanks everyone for your input.

cwl April 20, 2022 17:58

Quote:

Originally Posted by fluid23 (Post 826550)
This could leave pockets of unrefined mesh which could pose a problem when I move this from steady state initialization to unsteady.

You can just progressively refine the mesh in unsteady simulation as it runs - every N time steps or every delta time.
Or it there a problem with that which I miss? :confused:

fluid23 April 21, 2022 09:57

I suppose that process is relatively painless with adaptive mesh, but in the past that process was rather painful using field function tables. It required a lot of user interaction as I recall.

I just need to explore the adaptive mesh options, that sounds like the way to go.


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