Syntax of Boundary Condition Statements
Segment boundary conditions are added to the problem descriptor by placing them in the BOUNDARIES section.
Segment boundary conditions must immediately precede one of the reserved words LINE or ARC and cannot precede the reserved word TO.
A top-down system is used for applying segment boundary conditions to the equations. Following the START point specification in each path definition, a segment boundary condition is set up for each variable/equation. It is recommended that a boundary condition be specified for each variable/equation. If no other segment boundary condition is specified no error will occur and a NATURAL(VARIABLE) = 0 segment boundary condition is assumed.
Under the top-down system, as boundary segments occur, the previously specified segment boundary condition for a variable will continue to hold until a new boundary condition is specified for that variable.
If the recommendation is followed that REGION 1 be formed by walking the outside boundary of the problem, thereby enclosing the entire domain of the problem, then for most problems segment boundary conditions need only be specified for the segments in REGION 1.