Learning Forum

[Aras karimi]

Hello everyone,

Please help with a problem. I am optimizing the 3D shape of a wing using Fluent's adjoint solver. My mesh is structure type. During the optimization, the mesh elements lose their quality and are stretched in some areas, which causes errors in the solution. Can anyone help me what should I do?

I can access the deformed export geometry in STL format but I don't know how to mesh it ?

Thanks in advance for any help.

Regards,

Aras.

[Murari Iyengar]

If you are using Design Tool, then I recommend you start with a smaller change so you can see how the mesh is getting affected. Else, by using Gradient Based Optimizer, you can specify minimum cell quality and set target so Adjoint solver will automatically keep iterating till target/conditions are met. Please look at 43.2. Using the Adjoint Solver (ansys.com) for more information. 

[Murari Iyengar]

I also recommend checking the observable you've defined along with the target, morphing method, design conditions, region. You can find information regarding the same in the link attached above. 

If you want to mesh the .stl file, you can open it in any CAD software and continue as you normally would. 

[Aras karimi]

Thank you for your explanation. I have read the adjoint solver user guide and as you said the minimum cell quality can be specified so that the optimizer stops as soon as that defined value is reached. In order to perform a significant optimization on the geometry, the minimum cell quality is usually considered low so that the optimizer continues with more iterations. Now, in order to ensure the result obtained by the optimizer, it is necessary to remesh the geometry.

It was mentioned in the adjoint solver user guide ( Remeshing is required during optimization to achieve a well-designed and reliable geometry ). The adjoint solver automatically performs the remeshing process in 3D cases only on tetrahedral elements without a boundary layer, and unfortunately, it is not able to remesh on hexahedral elements, which is disappointing. Due to this limitation, the STL export geometry must be remeshed manually, and according to the investigations, the software is not able to create an structured mesh on the STL geometry.

I hope you will raise this issue in the Ansys group, what is the solution for remeshing the deformed geometry whose mesh is of the structured type.

It is hoped that this challenge of many engineers in this field can be solved.

Thankyou,

Regards.

 

 

[Murari Iyengar]

Unfortunately, at this time, we do not have a solution to this. It is a limitation that is being addressed and a solution will be implemented in the future.

[Aras karimi]

Is the limitation of not automatic Re-meshing of the adjoint solver for the structure mesh with hexahedral elements being solving?

If so, then another way must be chosen. The output geometry by the Fluent's adjoint solver is available as an STL file. How can I convert it to a structure mesh with hexahedral elements?