Apply Neumann boundary condition in a specific area, which is part of a surface

[dokken]

@Yanjun

g = 100 * ( (x[0]+214)**2 + (x[1]+27)**2 <= 324 && x[2] ==20 )

I would use ufl.conditional,
see for instance How to assign boundary conditions based on values of dolfinx.Function - #2 by dokken or Form compilation — FEniCS Tutorial @ Sorbonne