Learning Forum

[z5456415]

Hi,

I have a pitching airfoil (chord = 0.15m) simulation (pitches after a certain time using UDF). When I the simulation with Re = 2e6 (v = 197 m/s), at the beginning itself I am getting this message "turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 640565 cells". Also, the values for cl, cd, cm, etc are unrealistic huge values.

What could be the reason for this and how can I solve this? The model works under small velocity (v=10m/s).

 

Can anyone please help with this?

y+ value is below 1 and CFL set to 0.1.

Regards,

Muhammed Sadique

[Rob]

You may need to check inlet boundary conditions. Do the number of cells hitting the limiter reduce with iterations? 

[z5456415]

Hi Rob,

Thank you very much for your reply.

I did not check by changing the number of iterations. However, I changed the case with low velocity (10 or 30 m/s) and the simulation gives reliable results.

I do have another question about meshing. Please advise me if I have to post it separately in another thread.

When going for a fine mesh, or increasing the domain size, I am getting the following error,

“The specified defeaturing tolerance was found to be larger than a specified size. The elements on one or more edges may be defeatured out.”

Could you please tell me how I can resolve this? Though it shows the above error, a small portion of the domain is getting meshed properly.

Please find the image below, the geometry, where the domain with airfoil is getting meshed properly, where I thought the meshing will be complex and difficult.

[Rob]

I'd avoid odd shapes around a wing as you may trigger unwanted mesh resolution due to the curvature. Check defeaturing relative to smallest cell size. The check is to warn if you're trying to mesh to a greater resolution than you are simplifying the geometry to.