
While running a 3D transient free surface flow calculation with two planes of symmetry, symmetry planes may be progressively lost in the free jet, after several time steps (the calculation domain can be twisted). If the user runs the POLYDATA session with the keyword SPECIFY_SYMMETRY (in a .p3rc file or as an option defined in POLYMAN), she has the possibility to specify the direction perpendicular to the plane of symmetry, which will be kept unchanged throughout the calculation.If the desired symmetry planes are indeed perpendicular to an axis, an alternative is to replace the symmetry condition with vanishing forces, and redefining the symmetry through the use of submodels. Here, the appropriate Cartesian component of the velocity field must be set to zero, while vanishing force components are imposed along the two other directions.If the plane of symmetry is perpendicular to one of the axes, it is also possible to impose an additional constraint on the cooresponding coordinate through the mechanism of submodel. For example, if the plane of symmetry is perpendicular to the Ycoordinate, dY should be set to zero in the submodel.

