Civil Engineering Reference
In-Depth Information
Figure 3.9
Meshes generated by the coring method.
only the quality of the triangular elements near the boundary will be affected by the irregu-
larity of the domain. The main feature of this technique is to extract as much as possible
from the interior of the domain to form square elements, as in an excavation process, hence
the name
coring method
. The square elements can later be divided into triangular elements
to form a pure triangular mesh if necessary. Two examples of the coring method to produce
meshes of varying element size are shown in Figure 3.9.
3.3.3 Mesh refinement by subdivision
Generation of adaptive FE meshes by refinement can be achieved by selective subdivision of
triangles according to the specified node spacing function. Starting from a coarse mesh, ele-
ments can be subdivided progressively until the desired refinement is reached (Wordenweber
1984). The most popular type of division scheme is bisection of the longest edges, for which
the maximum and the minimum angles of the resulting triangles are bounded, and the process
will terminate in a finite number of steps (Rivara 1997). Many refinement algorithms with
various characteristics exist, and a comprehensive account can be found in a paper by Jones
and Plassmann (1997). As subdivision of triangles is a local process that does not require too
much computation, adaptive meshing by this approach in general is very efficient, although
the mesh topology and the general element layout are limited by the previous meshes. With
some post-treatment optimisation, the quality of the elements could be drastically improved;
nevertheless, the conformity to node spacing function is still restricted and may not be as
good as meshes generated from scratch in accordance with the given node spacing specifica-
tion. A gradation mesh produced by successive refinement is shown in Figure 3.10.
Figure 3.10
Mesh generated by refinement.
