format.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: grid format</TITLE>

<H1>Grid Format</H1>

 <P>We use a simple output format for grid output.

<H2>3D example</H2>

 <P>Let's consider the simplest 3D grid created by
 <A HREF="mainstarttest.html">our start example</A>.
It describes the unit cube, with 8 3D points,
6 tetrahedra, and 12 outer boundary triangles:

<PRE>
SimplexGrid 2.0
#created by wzgrid (c) I.Schmelzer
#Wed Sep 16 11:49:30 1998
DIMENSION
3
NODES
8 3
0.000000 0.000000 0.000000 
0.000000 0.000000 1.000000 
0.000000 1.000000 0.000000 
0.000000 1.000000 1.000000 
1.000000 0.000000 0.000000 
1.000000 0.000000 1.000000 
1.000000 1.000000 0.000000 
1.000000 1.000000 1.000000 
CELLS
6
8 7 1 5 1 -1 2 -2 4 
8 1 6 5 1 -3 -4 1 5 
8 1 3 4 1 -5 -6 6 4 
8 1 7 3 1 -7 -8 3 1 
8 2 6 1 1 -9 2 6 -10 
8 2 1 4 1 -11 3 -12 5 
FACES
12
7 1 5 1 -0 1 0 0 0 
8 7 5 1 -0 1 0 0 0 
1 6 5 1 -0 2 0 0 0 
5 6 8 1 -0 2 0 0 0 
1 3 4 1 -0 3 0 0 0 
4 3 8 1 -0 3 0 0 0 
1 7 3 1 -0 4 0 0 0 
3 7 8 1 -0 4 0 0 0 
2 6 1 1 -0 5 0 0 0 
2 8 6 1 -0 5 0 0 0 
2 1 4 1 -0 6 0 0 0 
8 2 4 1 -0 6 0 0 0 
END
</PRE>

 <P>For every cell (in 3D a tetrahedron) we have:

 <UL>
 <LI> the four nodes,
 <LI> the identifier of the region,
 <LI> the four neighbours.  If positive, it is a tetrahedron, if
negative, a face triangle.
 </UL>

 <P>For every boundary face element (in 3D a triangle) we have:

 <UL>
 <LI> the three nodes,
 <LI> the identifier of the boundary condition,
 <LI> left and right inner neighbour cells (-0 if it is an outer
boundary face),
 <LI> three neighbour face elements (currently not implemented, thus,
three times a 0 as a placeholder).
 </UL>

<H2>2D example</H2>

 <P>The same scheme is used for 2D grids:

<PRE>
SimplexGrid 2.0
#created by wzgrid (c) I.Schmelzer
#Wed Sep 16 12:09:00 1998
DIMENSION
2
NODES
4 2
0.000000 0.000000 
0.000000 1.000000 
1.000000 0.000000 
1.000000 1.000000 
CELLS
2
4 2 1 1 -1 2 -2 
4 1 3 1 -3 -4 1 
FACES
4
2 1 1 -0 1 0 0 
4 2 1 -0 1 0 0 
1 3 1 -0 2 0 0 
3 4 1 -0 2 0 0 
END
</PRE>

<H2>1D example</H2>

 <P>The same scheme is used for 1D grids too:

<PRE>
SimplexGrid 2.0
#created by wzgrid (c) I.Schmelzer
#Wed Sep 16 12:11:45 1998
DIMENSION
1
NODES
2 1
0.000000 
1.000000 
CELLS
1
1 2 1 -1 -2 
FACES
2
1 1 -0 1 
2 1 -0 1 
END
</PRE>

<H2>0D example</H2>

 <P>Formally even a 0D grid (a point) may be written in this format:

<PRE>
SimplexGrid 2.0
#created by wzgrid (c) I.Schmelzer
#Wed Sep 16 12:14:32 1998
DIMENSION
0
NODES
1 3
0.000000 0.000000 0.000000 
CELLS
1
1 1 
END
</PRE>