Dear Jun-yeong,
In Gmsh 3.0.6 the Surface() command duplicates the curves on its boundary,
which in your model leads to some duplicated 1D meshes (you can check by e.g.
displaying the line numbers in the gui).
Download the latest automated snapshot: this issue should be resolved. Attached
is
> On 28 Jan 2018, at 17:04, Christophe Geuzaine wrote:
>
>
> Dear Jun-yeong,
>
> In Gmsh 3.0.6 the Surface() command duplicates the curves on its boundary,
> which in your model leads to some duplicated 1D meshes (you can check by e.g.
> displaying the line numbers in the gui).
>
> Downloa