# Symmetry boundary condition¶

The symmetry boundary condition defines a mirror face/surface. The symmetry condition should only be used if the physical object or geometry and the expected flow field pattern of the developed solution is mirrored along that surface. This boundary condition helps to reduces the computational domain in size and enables the modeling of a sub-domain of the complete setup.

In general, the symmetry condition applies the following constraints on the flow variables:

• The fluxes across a symmetry are zero.
• The normal components of velocity are set to zero.
• The normal components of all other variables are set to zero.

The ‘symmetry’ boundary condition can be applied to both planer or non-planer faces/surfaces on the domain boundaries.

Important

For this boundary condition no input variables are required and all relevant variable are assigned the symmetry condition.

Important

This condition should not be used for axis-symmetric cases (see ‘Wedge boundary condition’ for details) or periodic flow cases (see ‘Periodic boundary condition’ for details).