[Janet]

I am meshing problem with airfoil having inward dimple. Dimple screenshot is attached.

https://ibb.co/MVWN7kb
https://ibb.co/bHKDP1R

My structured mesh is poor. I put a circle around the airfoil and generated the mesh, it was okay, but the small area around the dimple is still not okay and the Face Meshing has small blue sign on it suggesting something wrong in the mesh. Please guide.

[Gweher]

Hi Janet,

Please do not start 3 parallel threads for the same problem ...

There are a lot of threads showing the techniques to decompose the domain in order to generate a structured mesh.

If there is a blue sign on the Face meshing it means that it is not suitable for the applied selection. You need to decompose your geometry into smaller sub-surfaces (or sub-volumes if in 3D). In your case you should start with a C-grid around the airfoil. Then add splits around your discontinuity to properly capture your geometry shape.

Have fun

[Far]

Originally Posted by Janet

I am meshing problem with airfoil having inward dimple. Dimple screenshot is attached.

https://ibb.co/MVWN7kb
https://ibb.co/bHKDP1R

My structured mesh is poor. I put a circle around the airfoil and generated the mesh, it was okay, but the small area around the dimple is still not okay and the Face Meshing has small blue sign on it suggesting something wrong in the mesh. Please guide.

Why you dont try ICEMCFD?

[Janet]

Originally Posted by Gweher

Hi Janet,

Please do not start 3 parallel threads for the same problem ...

There are a lot of threads showing the techniques to decompose the domain in order to generate a structured mesh.

If there is a blue sign on the Face meshing it means that it is not suitable for the applied selection. You need to decompose your geometry into smaller sub-surfaces (or sub-volumes if in 3D). In your case you should start with a C-grid around the airfoil. Then add splits around your discontinuity to properly capture your geometry shape.

Have fun

Thank you Gweher. After several attempts I was able to get the structured mesh right. However, my solution is not getting converged. In the boundary conditions for inlet, I used components and 1xcosx6 (For x component) and 1xsinx6 for y component. Goes without saying this is for 6 degree angle of attack. My analysis is steady state and flow is inviscid.

I tried to find the solution at 1e-3 convergence criteria and I got it. While I tried 1e-6, the convergence is not happening even after 10,000 iterations.

And as I am simulating individually for different degree alpha, my convergence at 1e-3 was going okay from 0 to 8 degree angle of attack and these are all individual workbench projects, just as I started with 10 degree alpha, I wasn't able to converge the solution at 1e-3 even for 10,000 iterations. Why would that be?

Then I read somewhere I should try transient state simulation. I tried that and my solution was converged. May I get a good understanding of how transient state is able to converge my solution and how exactly does the time stepping is performed?

I guess I should stick to steady state but how to get the solution converged in it? Please help as this is very important for my project.

Besides, just need a confirmation if I am doing it all right. Once the solution is converged and I obtain the Cl and Cd, say for 6 degree alpha, I enter the following values:

For Cd: x = 1 cos 6 and y = 1 sin 6.
For Cl: x = 1 sin -6, y = 1 cos -6.

And thus I get the Cl and Cd at 6 degree alpha. Velocity is obviously 1m/s here. Am I doing it right?

[Janet]

Originally Posted by Far

Why you dont try ICEMCFD?

I have no experience working with ICECFD, only Fluent, but I am beginning to try that. Thank you for suggesting this which sounds like it might be relatively easier to simulate in ICEMCFD, is that so?

[Gweher]

Hi Janet,

As Far said, I would also recommend you to use ICEM CFD. It's a meshing software part of Ansys. Moreover in your case as you need to generate a mesh for different angles you could simply re-use the mesh generation script, importing the rotated geometry. For high angles you may need to adjust / change the blocking strategy used for your mesh generation.

Plus there are a lot of tutorials / help in this forum for airfoil mesh generation with ICEM CFD, you should definitively check them out.

Concerning the convergence problem, that's quite normal when you change your AOA. You should have a look at the fluent threats as it's a common question.

Have fun