Plethora of mesh questions

[Anonymous]

Hi, 

I am running a basic model of some control fins (purpose is to control a rocket while it lands) at various speeds (ideally 2-3 different supersonic speeds and 1-2 subsonic speeds) .  I'd like to measure the drag force only. I have some questions regarding the proper meshing though since I could not find tutorials related to my scenario. 

Would the Simulation Recommendations section of this article, be sufficient? How much layers would be sufficient for the Wall Layers tab (article says 10 but I dont know if that enough)? I can't figure out or get a ball park estimate of what would be sufficient for something for my case. 

When it comes to the Mesh Sizing, what size of the mesh would be useful? This article states to use 0.2 but again, I can't get a ball park estimate of what would be sufficient. 

Lastly, I would like to know if it would be appropriate to create a refined mesh region box around the control fins only? I attached some photos of my test runs (which I know is wrong) but I am confused as to when and where to put the mesh region box. How fine can my meshing be inside the box, if I can use it at all, before I start wasting computing power? 

If these questions can only be answered by testing mesh methods, can I have a link to a tutorial or article explaining the steps? 

Thanks. 

[Anonymous · Accepted solution]

Hi, 

When you use automatic mesh slider, it is relative to a parametric scale which is specific to geometry file. Parameter "0.2" is the default minimum, but you could go with 0.1 or less if you need to. 

http://help.autodesk.com/view/SCDSE/2019/ENU/?guid=GUID-C87366A9-0FBC-4940-B234-327588E85E0D

 

If you use refinement regions, it is great to use more that one region, to ensure good transition between your aimed superfine mesh and the remaining external mesh.

I put here some threads I've found useful: 

- https://forums.autodesk.com/t5/cfd-forum/questions-about-wall-layers-and-turbulence-models/td-p/8062...

- https://forums.autodesk.com/t5/cfd-forum/sst-kw-meshing-requirements/m-p/4505911#M2843

There is some webinars too that can be great to watch for your model: 

- https://www.youtube.com/watch?v=xAjIFWroJqE&t=833s&list=LL2UuBpXRYL1u7oz2_fDcCBw&index=14

- https://www.youtube.com/watch?v=N4z8HcBtL6U&t=0s&list=LL2UuBpXRYL1u7oz2_fDcCBw&index=9

- https://www.youtube.com/watch?v=Yf2iVABc8cg&t=0s&list=LL2UuBpXRYL1u7oz2_fDcCBw&index=12

I hope you can get answers with these. Try digging out all threads available. 

One last idea, you could try to use Adaptation Cycles solving tool here? I am not sure, but it could help to get the perfect grid.