Aras karimi

Due to the boundary condition used, the width of the domain must be equal to the width of the wing.

Before I subtract the wing from the domain, selecting the air domain once and the wing once from the Design Modeler tree diagram gives a representation like this:

As you can see, such a representation of geometry looks wrong and indicates a problem with geometry.

I think that this representation of the fragmented surface of the solid wing, which is provided by the mathematics used, is not just a representation, but actually the geometry of the STL file has been transformed into a solid body by connecting several pieces of the surface to each other, and it is very strange that Multiple levels cannot be merged.

Fragmentation of the wing surfaces creates many lines that are the boundary between the surfaces, which is misleading and creates problems for the meshing process.
Is there no way to make the wing a single surface ?

This figure (figure below) that you sent me earlier that showed a single surface for the wing , does it still show a single surface after importing it into Design Modeler ?