GID Tips

Adapting the Mesh

It is possible within GID to adapt specific regions of the mesh. For instance in a simple planar cell it is useful to adapt the mesh in the regions close the alignment layers where the change in splay is concentrated. Within GID it is possible to adapt lines, surfaces and volumes. The procedure for adapting a surface is outlined below:
1) Meshing ? Assign unstruct. sizes ? Surfaces
2) Now you will be prompted to enter the tetrahedra side length you want in the adapted region
3) Now select the surface to which this adaptation should be applied.
4) Regenerate the mesh
In the preferences - from the upper menu, you can select the speed of the transition between element sizes. This is in ‘Meshing’ - ‘Unstructured size transitions’.

Shortcuts

For simple structures you can get GID to create the surfaces and volumes automatically for you from the lines. Firstly create the points and the lines of the structure. You can then generate the surfaces that are made up of 4 (for example) lines. Click on from the left hand menu. Then right click on the background and select Contextual ? Automatic then type in ‘4’ and click ok. The surfaces should now appear. The same can now be done for the volumes. Click on from the left hand menu. Again right click on the background and select Contextual ? Automatic struct.

Batch Files

If you require want to make multiple change to a structure, such as changing the thickness, it is possible to scale the structure within GID. Unfortunately whilst this seems to recalculate the points correctly, the associated surfaces and volumes are often not properly recalculated. For this reason it is often simplest to use the batch processing command available in GID. The structure of the batch files is poorly document, and it is best to record a macro within GID to determine the batch command. Some modification of the recorded code is often necessary to create a batch file that actually runs!

1) Utilities?Graphical?Macros
2) Click the button
3) Create the structure or assign boundary conditions within GID
4) Press .
5) The commands you have just performed will appear in the ‘Current Macro Code’ edit box.
6) Copy this code into a text file.
7) This text file can be then be executed: File(?Import) ?Read Batch File

It is often necessary to modify the code slightly by adding additional escapes after each command (three escapes is the normal requirement!). An example of the code required to assign the problem type and then set two surface to the boundary condition FixLC-1_Electrode-1 is given below:

data defaults ProblemType yes problem_type_LC2
escape
escape
escape
data mat assign FixLC-1_Electrode-1 Surfaces
1
3
escape
escape
escape

This page last modified 2 June, 2006 by r.james