[snappyHexMesh] snappyhexmesh: addLayersControls and paraview

wizard1301 · March 25, 2009, 09:48

Hi
I'm trying to add layers on a surface with snappyhexmesh;
I haven't well understood the meaning of all the parameters of the addLayersControls dict and most important I'm not able to see the layers with paraview.
Can someone help me?

Thanks
Antonio

waterboy · March 25, 2009, 10:16

Hi,
Whats the problem?
1.)If You know what the height of the first layer should be You can easily estimate what refinement level brings You close. 1 Refinement halfes the basisc edge legth. If You then decide how many layers you want and the increase in thickness named expansionRatio You can calculate how thick the latest layer is compared to the outside mesh. I usually calculate these values starting with some y+ estimations and play around with number of layers and expansionFactor.
2.) I believe it is best to export the addedCells set to VTK to use with paraView. Like this You can see it over Your original geometry stl and see if it covers the area You wanted...Of course this works in paraFoam too, just select sets, but at my computer at work it doesn't run:-(

Have fun,
Pal

wizard1301 · March 25, 2009, 10:26

Thank you for your fast reply Pal;
about paraview, I noticed that if I view the whole mesh and the added cells at the same time in paraview (obviously for both the datasets from the same time directory) they are not consistent; the whole mesh extend till the stl suface and the added cells are ON the whole mesh

Antonio

waterboy · March 25, 2009, 10:34

Antonio,
i am not sure I understood what You meant to say. The addedlayer is part of the mesh, the original mesh is shrunk to provide the space for the layer. Is that what You mean?
Maybe You can send a picture with the mesh and the addedcells in another color,
(please no red/green combination)
Pal

wizard1301 · March 25, 2009, 10:46

The image of the grid.
It seems that the grid is not shrunk. The mesh in the picture is a visualization of the VTK obatined running foamToVTK on the final directory obtained with snappyhexmesh

waterboy · March 26, 2009, 03:09

Hi Antonio,
Sorry for leaving yesterday without notice, I was occupied by my own simulation....
The image looks strange but it may be because of the vsualization in paraview. Can You make a picture of the addedLayers in 3D and the rest of the mesh as a slice. Or even better the original STL with the cover of addedlayers in a different color?
Hope this helps,
Pal

wizard1301 · March 26, 2009, 04:57

Hi Pal
thank you very much for your help; I found where I was wrong, there were a problem with some settings for the version of paraview used. For a reason that I don't understand the slice is not at the desired position. This morning I tried with a different version of paraview and everythings works well (Yesterday I was working with a version of paraview that I've customized, probably I've introduced some bug...). Sorry for the all time.

thanks

Antonio

March 25, 2009, 09:48	snappyhexmesh: addLayersControls and paraview	#1
wizard1301 New Member Antonio Attili Join Date: Mar 2009 Location: Rome, Italy Posts: 21 Rep Power: 17	Hi I'm trying to add layers on a surface with snappyhexmesh; I haven't well understood the meaning of all the parameters of the addLayersControls dict and most important I'm not able to see the layers with paraview. Can someone help me? Thanks Antonio

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March 25, 2009, 10:16		#2
waterboy New Member Pal Schmitt Join Date: Mar 2009 Posts: 28 Rep Power: 17	Hi, Whats the problem? 1.)If You know what the height of the first layer should be You can easily estimate what refinement level brings You close. 1 Refinement halfes the basisc edge legth. If You then decide how many layers you want and the increase in thickness named expansionRatio You can calculate how thick the latest layer is compared to the outside mesh. I usually calculate these values starting with some y+ estimations and play around with number of layers and expansionFactor. 2.) I believe it is best to export the addedCells set to VTK to use with paraView. Like this You can see it over Your original geometry stl and see if it covers the area You wanted...Of course this works in paraFoam too, just select sets, but at my computer at work it doesn't run:-( Have fun, Pal

March 25, 2009, 10:26		#3
wizard1301 New Member Antonio Attili Join Date: Mar 2009 Location: Rome, Italy Posts: 21 Rep Power: 17	Thank you for your fast reply Pal; about paraview, I noticed that if I view the whole mesh and the added cells at the same time in paraview (obviously for both the datasets from the same time directory) they are not consistent; the whole mesh extend till the stl suface and the added cells are ON the whole mesh Antonio

March 25, 2009, 10:34		#4
waterboy New Member Pal Schmitt Join Date: Mar 2009 Posts: 28 Rep Power: 17	Antonio, i am not sure I understood what You meant to say. The addedlayer is part of the mesh, the original mesh is shrunk to provide the space for the layer. Is that what You mean? Maybe You can send a picture with the mesh and the addedcells in another color, (please no red/green combination) Pal

March 26, 2009, 03:09		#6
waterboy New Member Pal Schmitt Join Date: Mar 2009 Posts: 28 Rep Power: 17	Hi Antonio, Sorry for leaving yesterday without notice, I was occupied by my own simulation.... The image looks strange but it may be because of the vsualization in paraview. Can You make a picture of the addedLayers in 3D and the rest of the mesh as a slice. Or even better the original STL with the cover of addedlayers in a different color? Hope this helps, Pal

March 26, 2009, 04:57		#7
wizard1301 New Member Antonio Attili Join Date: Mar 2009 Location: Rome, Italy Posts: 21 Rep Power: 17	Hi Pal thank you very much for your help; I found where I was wrong, there were a problem with some settings for the version of paraview used. For a reason that I don't understand the slice is not at the desired position. This morning I tried with a different version of paraview and everythings works well (Yesterday I was working with a version of paraview that I've customized, probably I've introduced some bug...). Sorry for the all time. thanks Antonio