OOF2: The Manual

Details

Description

EdgeFromElements is a BoundaryConstructor, used as the constructor argument of the OOF.Skeleton.Boundary.Construct command when building Skeleton boundaries. It creates Edge Boundaries from the currently selected Skeleton Elements or from a group of Elements. The Elements are specified by the group parameter, which must be either the name of an Element group or the special placeholder object, selection.

The boundary is constructed from the Segments that are on the perimeter of the given group of Elements. Segments that are shared by two Elements in the group will not form part of the boundary. It is not possible to construct an edge boundary from a set of non-contiguous Elements.

Edge boundaries must be constructed from a single contiguous non-branching set of Segments, and they must be directed. Boundary conditions use the direction to determine the boundary normal and the direction of applied Fields and Fluxes. The direction parameter specifies the direction of the boundary being created. The legal values for direction generally depend on the topology of the boundary being constructed. The edges bounding a set of Elements always form a closed loop, so the legal values of direction are 'Clockwise' and 'CounterClockwise'.

Figure 6.73 shows some examples of edge boundaries created from Elements, and of sets of Elements from which it's impossible to create boundaries.

Figure 6.73. Constructing an Edge Boundary from Elements

(a) A Skeleton with some selected Elements (in green).

(b) An edge boundary created with

          OOF.Skeleton.Boundary.Construct(
             skeleton='swoops.png:skeleton',
             name='boundary',
             constructor=EdgeFromElements(
                group=selection,
                direction='Clockwise'))

Note that only the outer boundary of the selected elements has been used to construct the boundary.

(c) The boundary is necessarily closed, so the allowed directions are Clockwise and Counterclockwise.

(d) and (e) illustrate Element selections (in green) that cannot be used to create an edge boundary. The segments on the exterior of the green regions do not form a single sequence.

(f) The dialog box now offers no choices for direction and the OK button is disabled.

See Also