surfacegrids.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: surface grids</TITLE>

<H1>Surface Grids</H1>

 <P>COG 2.0 creates surface grids as for the outer boundary, as for
inner boundary faces.  These surfaces match the inner tetrahedral
grids, for inner boundaries the inner grids on above sides.

 <P>But the quality of these surface grids may be not appropriate for
boundary element methods.  The main purpose of the COG package is to
obtain good grid quality inside the regions. The surface grid is a
useful side effect, and necessary to define boundary conditions. But
to optimize its quality was not the aim of the package.

 <P>The surface points are computed as intersections with the
coordinate lines of the coordinates inside the region.  That means,
for a curved surface (here: sphere) but rectangular coordinates we
obtain a surface grid like this:

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

 <P>Note that some surface triangles have very small angles.

 <P>In future, I will try to avoid very small angles if possible, but
the main algorithm, and, thus, the general picture, remains the same.

 <P>You have to create appropriate <A HREF="mainpolartest.html">curved
coordinates</A> for a surface to obtain an appropriate, regular
surface grid.