Learning Forum

[goktug.yilmaz]

Hi all,

I am conducting airfoil analysis using Fluent and I am facing convergence issues when attempting to set the y+ value to 1. I have tried various turbulence models and methods, but the problem persists.I am unsure if this issue is due to mesh quality or any other reason. As of now, I'm unable to identify the exact cause of the problem. However, I suspect that there may be some underlying issues with the mesh.

Has anyone faced a similar issue before or can anyone suggest some methods to improve the convergence in this case? Should I try using a different turbulence model or any other approach?

Any help would be appreciated.

Here are some mesh metrics that I obtained:

Orthogonal Quality: Min: 4,29E-05   Average: 0,69  Max: 0,99

Aspect Ratio: Min: 1,171  Average: 1133,6 Max: 39380

Skewness: Min: 1,46E-3  Average:0,2345  Max: 0,99

Element Quality: Min:5,3E-5  Average:0,26 Max: 0,99

Jacobian(MAPDL): Min:1 Average: 1,017 Max: 2,6

Jacobian(Corner Nodes): Min: 0,3852 Average: 0,9852 Max:1

Jacobian(Gauss Points): Min:-1 Average:2,9776   Max:55625 

 

Thanks in advance!

 

[Federico Alzamora Previtali]

Hello,

you should aim for maximum Orthogonal quality to be below 0.9 and maximum skewness below 0.7-0.8. Also, your aspect ratio appears to be too large. Did you generate this mesh?

We have an Ansys Innovation Course on compressible flow over an airfoil Compressible Flow Over An Airfoil | Ansys Innovation Courses. There is a mesh file provided. Perhaps you could have a look at it as reference.

Bests,

Federico

[Rob]

I'd start by fixing the mesh.  The y+ concept is abused, misunderstood and isn't the only thing you need to consider: what does the flow do in the cells that aren't next to the wall? In CFD we look at ortho quality (usually for polyhedral cells), skewness (0 to about 0.8 is good, over 0.95 is bad) and aspect ratio (ranges vary, up to a few hundred are OK in a developed flow, 5 is high if the flow changes along the long edge of a cell).