The Symmetry boundary condition prescribes a no-penetration condition, u ⋅ n = 0. This node sets the same flux condition as the Wall feature.

For 2D axial symmetry, a boundary condition does not need to be defined for the symmetry axis at r = 0. The software automatically provides an Axial Symmetry node prescribing u ⋅ n = 0 on the axial symmetry boundaries.