G := {(x,y,z)| 1 < (x/rx)² + (y/ry)² < a²; 0 < z < L }
where rx=1, ry=0.5, a=2, L=5. (This resembles a section of an elliptic hollow cylinder.)Δ u = 0 in G.
u(x,y,z) = (|x,y|-1)(a-|x,y|)(L-z)/L at δG
with|x,y|:=sqrt( (x/rx)² + (y/ry)² ).
Q:={(x,y,z)∈G| x>0; y>0}
of G is used. At the additional boundaries at x=0 and y=0 natural boundary conditions are imposed (These are the default boundary conditions in ff3d therefore no additional statement is needed in the ff3d input file).