DSYM, Lab, Normal, KCN
Specifies symmetry or antisymmetry degree-of-freedom
constraints on nodes.
LabSymmetry label:
SYMM | — | Generate symmetry constraints as described below (default). |
ASYM | — | Generate antisymmetry constraints as described below. |
NormalSurface orientation label to determine the constraint set
(surface is assumed to be perpendicular to this coordinate direction in coordinate
system KCN):
X | — | Surface is normal to coordinate X direction (default). Interpreted as R direction for non-Cartesian coordinate systems. |
Y | — | Surface is normal to coordinate Y direction. θ direction for non-Cartesian coordinate systems. |
Z | — | Surface is normal to coordinate Z direction. Φ direction for spherical or toroidal coordinate systems. |
KCNReference number of global or local coordinate system used to define surface orientation.
Specifies symmetry or antisymmetry degree-of-freedom constraints on
the selected nodes. The nodes are first automatically rotated (any previously
defined rotations on these nodes are redefined) into coordinate system KCN,
then zero-valued constraints are generated, as described below, on the selected
degree-of-freedom set (limited to displacement, velocity, and magnetic degrees
of freedom) [DOFSEL]. Constraints are defined in the (rotated)
nodal coordinate system, as usual. See the D and NROTAT commands
for additional details about constraints and nodal rotations.
This command is also valid in PREP7.
Symmetry or antisymmetry constraint generations are based upon the valid
degrees of freedom in the model, i.e., the degrees of freedom
associated with the elements attached to the nodes. The labels for degrees
of freedom used in the generation depend on the Normal label.
For displacement degrees of freedom, the constraints generated are:
| SYMM | ASYM | |||
|---|---|---|---|---|
Normal | 2-D | 3-D | 2-D | 3-D |
| X | UX, ROTZ | UX, ROTZ, ROTY | UY | UY, UZ, ROTX |
| Y | UY, ROTZ | UY, ROTZ, ROTX | UX | UX, UZ, ROTY |
| Z | -- | UZ, ROTX, ROTY | -- | UX, UY, ROTZ |
For velocity degrees of freedom, the constraints generated are:
| SYMM | ASYM | |||
|---|---|---|---|---|
Normal | 2-D | 3-D | 2-D | 3-D |
| X | VX | VX | VY | VY, VZ |
| Y | VY | VY | VX | VX, VZ |
| Z | -- | VZ | -- | VX, VY |
For the 2-D vector magnetic degree of freedom, AZ, symmetry is naturally satisfied and the SYMM label generates no constraints. The ASYM label generates flux parallel conditions (flux flows parallel to the surface).
| SYMM | ASYM | |
|---|---|---|
Normal | 2-D | 2-D |
| X | -- | AZ |
| Y | -- | AZ |