[cfMesh] edge detection (solved!)

zordiack · December 1, 2015, 09:15

Hi, lately I've been having a lot of trouble with cfMesh edge detection. The mesh is fine otherwise, but sharp edges are not conformed or "snapped". I have the original geometry in a file whole.stl, and I'm using the following command to detect edges:

Code:

surfaceFeatureEdges -angle 120 whole.stl whole.fms

The file whole.fms is then used as an input for cfMesh meshDict. I've attached a picture to show the problem, where the surface file whole.stl and generated mesh are shown in paraview.

Any help? Is this the correct way to use edge detection with cfMesh or is there a better way? I don't recall having this problem before, but I might just have been lucky. I'm using OpenFOAM-dev with cfMesh 1.1.1.

zordiack · December 1, 2015, 09:51

Okay this is (again) going to be one those post where I correct myself. It turns out I've been using the included angle option the wrong way around. It doesn't work the same way as in snappyHexMesh. So if you want to include i.e. all edges with at least 90 degree angle, you should use a SMALLER than 90 degrees angle specification with surfaceFeatureEdges, or just use the default (which is 45 degrees):

Code:

surfaceFeatureEdges whole.stl whole.fms

I'm happy to report that the edge detection is working again, when I use it correctly

Here is the same mesh with correct edge detection:

franjo_j · December 5, 2015, 16:12

You can inspect the feature edges by using:

FMSToSurface <inputSurfaceMesh>.fms <outputSurface> -exportFeatureEdges

-exportFeatureEdges writes feature edges in a vtk file, which you can visualize in ParaView.

zannatul · February 4, 2016, 14:43

Can you please tell me why it is saying to me that surfaceFeatureEdges command not found?

franjo_j · February 5, 2016, 06:31

Hi,

Quote:

Originally Posted by zannatul

Can you please tell me why it is saying to me that surfaceFeatureEdges command not found?

surfaceFeatureEdges is part of cfMesh. It seems to me that you do not have cfMesh available in your environment or your OF environment is not set up correctly.

zannatul · February 5, 2016, 13:08

Quote:

Originally Posted by franjo_j

Hi,

surfaceFeatureEdges is part of cfMesh. It seems to me that you do not have cfMesh available in your environment or your OF environment is not set up correctly.

Yes may be that is the thing. Thank you for your response

December 1, 2015, 09:15	edge detection (solved!)	#1
zordiack Member Pekka Pasanen Join Date: Feb 2012 Location: Finland Posts: 87 Rep Power: 14	Hi, lately I've been having a lot of trouble with cfMesh edge detection. The mesh is fine otherwise, but sharp edges are not conformed or "snapped". I have the original geometry in a file whole.stl, and I'm using the following command to detect edges: Code: surfaceFeatureEdges -angle 120 whole.stl whole.fms The file whole.fms is then used as an input for cfMesh meshDict. I've attached a picture to show the problem, where the surface file whole.stl and generated mesh are shown in paraview. Any help? Is this the correct way to use edge detection with cfMesh or is there a better way? I don't recall having this problem before, but I might just have been lucky. I'm using OpenFOAM-dev with cfMesh 1.1.1. Last edited by zordiack; December 1, 2015 at 09:55. Reason: corrected title

December 1, 2015, 09:51		#2
zordiack Member Pekka Pasanen Join Date: Feb 2012 Location: Finland Posts: 87 Rep Power: 14	Okay this is (again) going to be one those post where I correct myself. It turns out I've been using the included angle option the wrong way around. It doesn't work the same way as in snappyHexMesh. So if you want to include i.e. all edges with at least 90 degree angle, you should use a SMALLER than 90 degrees angle specification with surfaceFeatureEdges, or just use the default (which is 45 degrees): Code: surfaceFeatureEdges whole.stl whole.fms I'm happy to report that the edge detection is working again, when I use it correctly Here is the same mesh with correct edge detection: Krapf and lukasf like this.

December 5, 2015, 16:12		#3
franjo_j Senior Member Franjo Juretic Join Date: Aug 2011 Location: Velika Gorica, Croatia Posts: 124 Rep Power: 16	You can inspect the feature edges by using: FMSToSurface <inputSurfaceMesh>.fms <outputSurface> -exportFeatureEdges -exportFeatureEdges writes feature edges in a vtk file, which you can visualize in ParaView. zordiack, Krapf and lukasf like this. __________________ Principal Developer of cfMesh and CF-MESH+ www.cfmesh.com Social media: LinkedIn, Twitter, YouTube, Facebook, Pinterest, Instagram

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February 4, 2016, 14:43		#4
zannatul New Member Nila Join Date: Oct 2014 Posts: 24 Rep Power: 11	Can you please tell me why it is saying to me that surfaceFeatureEdges command not found?