It has been a very long time since I used Butterfly or checked the source code so I cannot really help but I think you are on the right direction and at this point this is more of a OpenFOAM question than a Butterfly question which you can most likely post to an OpenFOAM forum.
Hi，@mostapha Thank you for the prompt reply.
Indeed this is a OpenFoam question.The boundary file in constant/polyMesh folder is the key,after I set the type from wall to symmetry it works perfectly.
My original idea was to create a symmetric plane automatically via butterfly,so I posted here for some idea, and then I modified the source code of butterfly,added some functions like “make2d”.
I am not sure it is a correct way to set a symmetric plane via butterfly,anyway,it create a symmetric plane automatically and works perfectly now.