Page 226 - Basic Structured Grid Generation

Unstructured grid generation 215

5
6 4

10
11 3
8
7 7 2 3
4
9 2
6
1
5
8
1
Fig. 8.38 Ninth front.

5
6 4
12
11
10
9 3

8
7 7 2 3
4
2
6
1
5
8
1
Fig. 8.39 Completed triangulation.

If the algorithm is applied for a further four stages, the shortest face being chosen
at each stage, we arrive at the triangular grid shown in Fig. 8.39, in which the front
has finally disappeared and the following properties can be deduced:

• active nodes: none
• active sides: none
• passive nodes: 1, 2, 3, 4, 5, 6, 7, 8
• passive sides: 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-1
• npoint: 11
• nelem: 12
• nptr: none

Note that, in general, when a new point is found to be very close to an active node
on the front, it is replaced by this node. This avoids having to deal with a triangular
cell with a very small edge at some later stage.