PERBC
Bulk Data Entry Defines a connection between opposite edges/faces of the structure. This entry is used to apply Periodic Boundary Conditions to the model.
Format
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
|---|---|---|---|---|---|---|---|---|---|
| PERBC | ID | GSID | RLID | TOL |
Example
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
|---|---|---|---|---|---|---|---|---|---|
| PERBC | 2 | 45 | 32 | 0.01 |
Definitions
| Field | Contents | SI Unit Example |
|---|---|---|
| ID | Set identification
number. (Integer > 0) |
|
| GSID | Identification number
of a SET of grid points on one side of the
structure. (Integer > 0) |
|
| RLID | A RELOC Bulk Data Entry
identification number that maps the nodes on one side of the
structure to the other. An exact one-to-one match between the
two sides is required. (Integer > 0) |
|
| TOL | Specifies the numeric
value defining the maximum distance between two grid points to
allow equivalence. All grid points in the set defined by
GSID and the set of grid points on the
other side of the structure (mapping defined by the
RELOC entry) are considered for
equivalence based on the tolerance. (Real > 0.0) |
Comments
- The PERBC entry can be used to apply periodic boundary conditions, to match results from one side of the structure to another.
- The referenced RELOC Bulk Data Entry should be defined with TYPE=MOVE or TYPE=ROTATE. For TYPE=ROTATE, a simple rotation about a single axis should only be defined. All grids on one side of the structure (defined via GSID) and matching grids on the other side cannot have a coordinate system (field CD on GRID entry) defined. If RELOC(ROTATE) is specified, then all matching grids on both sides must have a cylindrical coordinate system assigned with the Z-axis matching the axis used for RELOC rotation.
- Periodic Boundary Conditions are supported for all solution sequences (except OptiStruct-Multibody Dynamics (OS-MBD) and Geometric Nonlinear Analysis (ANALYSIS=EXPDYN)) and all optimization types. In shape optimization, when GRID's identified on the PERBC entry are in or near the optimized zone, their location changes should be properly linked through DVGRID, otherwise the results may be incorrect.