matchproblem.html

有限元学习研究用源代码(老外的),供科研人员参考

<TITLE>COG 2.0: match problems</TITLE>

<H1>Match Problems</H1>

 <P>If we use different systems of coordinates, the most critical part
of the grid is the transitional region between different coordinates.

 <P>If the grid is isotropically refined in above regions there is
usually no problem. The problematic case is anisotropical refinement,
if the two neighbour grids do not match in the "coarse" direction. The
resulting grid has bad grid quality, moreover, the geometry may become
incorrect (region cells intersecting a boundary face):

 <P><IMG SRC="matchproblem.gif">

 <P>The following strategies may be used to solve this problem:

 <UL>
 <LI> Using isotropical refinement near the boundary of each grid. 
 <LI> Moving the transitional region away from boundary faces. In this
case, at least the boundaries will not be perforated.
 <LI> In 2D it often helps to modify the coarse grid with explicit
intersection planes.  There are different substrategies: 

 <P>The first is to create a matching point in the other grid, for
example by introduction of a matching plane in tangential direction.

 <P>The other is to "move away" the problematic nodes by introducing
or moving coarse grid planes in the orthogonal direction (has been
used <A HREF="mainshuktest.html">here</A>).
 <LI> Especially in 3D it makes sense to use corresponding coordinates
and coarse grid points in the "coarse" direction. An example may be
seen <A HREF="mainoiltest.html">here</A>.
 </UL>