CFD Online Discussion Forums

CFD Online Discussion Forums (
-   OpenFOAM (
-   -   extrudeMesh - stop edge and cell removal (

drrbradford August 23, 2011 06:31

extrudeMesh - stop edge and cell removal
2 Attachment(s)
I'm having problems with sweeping a 2D mesh.

I need to change to the threshold for the lengths below which the edges and cells are removed automatically by the collageEdges part of the extrudeMesh utility.

I have altered the mergeDim value in extrudeMesh.C to a very small number (1E-20 * d) but this didn't make any difference and I'm not really comfortable with changing any more code that I don't understand.

Can anybody direct me as to where I can alter this threshold value?


I've attached screenshots of the problems it causes. The first is the 2D mesh I would like to sweep. The second is a clip plane showing the problems that deletion of small volumes causes with the geometry.

drrbradford August 23, 2011 06:39

A little more info:

When I run extrudeMesh I get the following type of message:


Merging edge (8530 8531) since length 0 << 0.042625
In this case, the 0 refers to the removal of the edges created at the axis of rotation (I assume). It is the value of "0.042625" I would like to alter.

drrbradford August 23, 2011 08:53

Converting the mesh to metres from mm was a good start. However, I'm still having problems with the small volumes in the boundary layer, close to the axis of rotation.

drrbradford August 24, 2011 11:19

I've solved the problem and have learned a tiny bit about programming while I've been at it.

For anyone who needs to deal with this in future:

1. Change mergeDim value in the file /OpenFOAM-X.Y.Z/applications/utilities/mesh/generation/extrude/extrudeMesh/extrudeMesh.C to some appropriate value. Don't make it too small if you still want to remove the singularities created at the axis of symmetry.

2. Delete the file applications/utilities/mesh/generation/extrude/extrudeMesh/Make/<PLATFOM>/extrudeMesh.o

3. Open a terminal in the applications/utilities/mesh/generation/extrude/extrudeMesh/ directory and run wmake.

Boom, threshold changed.

All times are GMT -4. The time now is 14:15.