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.