NREFLECT (Non-Reflecting Boundary)

Description

The NREFLECT entry specifies faces that define a non-reflecting boundary on solid elements. An incident wave encountering a non-reflecting boundary “passes” through the boundary without being reflected. The boundary must be defined by exterior faces on solid elements.

The definition of the segments defining a non-reflecting surface follows the same rules as the definition of a BSSEG surface. Either 4-node quadrilateral faces or 3-node triangular faces may be defined A triangular segment is defined by specifying a zero or blank grid ID for the fourth node.

The segments defining the surface should all have their outward normal defined such that they point out of the solid body (towards the semi-infinite medium). The outward normal for the segments is defined by the usual counter-clockwise orientation of the grid point number on each segment.

Format

1	2	3	4	5	6	7	8	9	10
NREFLECT	SID	G1A	G2A	G3A	G4B	G1B	G2B	G3B
	G4B	G1C	G2C	G3C	G4C	-etc.-

Example

NREFLECT	100	204	201	202	203	203	202	199
	198	198	199	196	197	197	196	195
	194

Field	Definition	Type	Default
SID	Set identification number for the nonreflecting boundary.	Integer > 0	Required
Gi	Grid points defining the face.	Integer ≥ 0	See Remarks 1 and 2

Remarks

1. If the face is a quadrilateral face (four nodes), each of the Gi are unique grid point identification numbers. If the face is a triangular face (three nodes), then G3 is equal to G4. A triangular face can be specified by skipping (leave blank) the 4th node GID or by repeating the 4th node GID as the same as the 3rd node GID.
2. A sequential, counter-clockwise numbering of the grid point identification on the face defines the positive normal for the facing pointing in the exterior direction.