Lesson 7

Lesson 7 : Using Mesh Generator

The current release of OFELI is not provided within a native mesh generator. For this, we prefer to add to the package a public domain mesh generator that we have interfaced with OFELI classes. The included mesh generator is called BAMG. It was developed by an INRIA team.

To generate a 2-D finite element mesh you have to use the class Domain to create a domain and then call the function BAMG that generates a mesh file in the MDF format. The following example contained in the OFELI package illustrates a typical usage of the mesh generator. It uses the program GenMesh created while you install the utilities

An example

We now give an example of DDF (Domain Data File) to generate a domain and then a mesh

#DOMAIN!
vertex  1   0   0  0.3  21
vertex  2  20   0  0.3  01
vertex  3  20   9  0.3  01
vertex  4   0   9  0.3  21
vertex  5   4   4.5  0.2  11
vertex  6   5   4.5  0.2  11
line  1  1  2  01  0 40  1
line  2  2  3  01  0 20  1
line  3  3  4  01  0 40  1
line  4  4  1  21  0 20  1
circle  5  5  6  5.0  5.0  0.25  -1  11  0  20
circle  6  6  5  5.0  5.0  0.25  -1  11  0  20
contour  4  1  2  3  4
hole  1  2  5  6
mesh hole
EOF

The above text file enables generating a rectangular domain containing a circular hole. Although DDF files are described in detail later, we will comment out the file contents

The first line in DDF files starts with the string #DOMAIN!
Lines with the keyword vertex define vertices of the domain
Lines with the keyword line define lines that join vertices
Circles are defined by appending two (or more) circular arcs
The 2-D domain is defined as a contour (external boundary) and a union of holes
The line starting with keyword mesh tells that the resulting mesh must be stored in a file called hole.d
Finally, keyword EOF ends the file

Once this file is created and called hole.d, we can generate the file hole.m by typing

   GenMesh hole.d