Learning Forum

[Metin]

Hello,

I created a poly-hexcore mesh with Ansys Fluent and I'm getting the error "Min. aspect ratio less than 1". This error can be seen when Fluent is creating the prisms and my solution diverges. What is the reason of this error? I know max. aspect ratio, but min. aspect ratio confuses me.

Best Regards,

Metin

[Metin]

Also I realized that I have 2 bodies of lnfluence in my mesh and they overlap. Could this be the reason of this error?

[Rob]

Not sure how you can have an aspect ratio of less than one! How does the skew look? I know poly cells can get scrambled if the cell height is very small due to the way the poly extrusion works but that usually fails the ortho quality check first.
Overlapping BOI shouldn't cause any mesh issues other than slowing it down a little if they're giving conflicting sizing.

[Amine Ben Hadj Ali]

Screenshot of the error message.

[Amine Ben Hadj Ali]

You can add an improve volume mesh task and try again.

[Metin]

My orthogonal quality is 0,08 and max. skewness is 0.89. My first cell height is 5e-6 meters and I used 20 inflation layers with a 1.2 growth rate. I used "Check Quality" and "Check Case" in the solution section but there isn't a single error. I can see the aspect ratio error only in FLUENT meshing even though the smallest aspect ratio one can achieve is 1 !
Another thing I would like to add is that I used merge cell zones when I was auto-meshing. I also saw that when I set some prism layers, some options are grayed out in Poly-Hexcore meshing.

I'm not using task workflow, so I would appreciate if you could tell me how to improve volume mesh manually.

[Amine Ben Hadj Ali]

6.2.16. Improving the Volume Mesh (ansys.com)

[Metin]

So I couldn't solve my problem after trying to volume mesh improving techniques. But I would like to know how to use body of influence in Fluent Mesher.
1- I have a rectangular domain which has a wing in it. I have another body inside the domain which is used as BOI.
2- I removed the wing from the domain with boolean in Design Modeler. I didn't remove anything from the BOI. I didn't use share topology in DM either.
What are the steps I should follow in order to create my mesh properly? I have the sizings I need and I feel like I'm making some other mistake like choosing a wrong method for BOI in Fluent Mesher. I use the same sizings in Ansys Mesher and it works just fine. When I use those sizings in Fluent Mesher, the mesh looks good and it passes quality checks but it gives terrible results (it diverges in 100 iterations or so). I must be making a fundamental mistake here within Fluent Mesher. Could you help me find the problem please?

[Metin]

Should I use Share Topology in Design Modeler if I bring geometries from another CAD software? I have 2 bodies which are the domain and the BOI.

[Rob]

Click on Help in Fluent and look at the tutorials.