boundary condition in openfoam
 

Hi

I have very problem with boundary condition in openfoam. I think they are very confusing. I cant' understand difference between primitive and derived Bc. in openfoam!!!?? when I must use primitive Bc and when use derived ones?!!

also, I need to write a new boundary condition, but I don't know to use it, can anyone help me? it seems that I must compile it first but don't know to compile a new code. plz help me.:(
Thank you.