extrudeMesh - stop edge and cell removal

drrbradford · August 23, 2011, 06:31

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?

Cheers.

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:

Code:

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.

August 23, 2011, 06:39		#2
drrbradford Member Daniel Join Date: Apr 2010 Location: Manchester Posts: 30 Rep Power: 16	A little more info: When I run extrudeMesh I get the following type of message: Code: 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.

August 23, 2011, 08:53		#3
drrbradford Member Daniel Join Date: Apr 2010 Location: Manchester Posts: 30 Rep Power: 16	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. Last edited by drrbradford; August 23, 2011 at 09:22.

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August 24, 2011, 11:19		#4
drrbradford Member Daniel Join Date: Apr 2010 Location: Manchester Posts: 30 Rep Power: 16	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.