[snappyHexMesh] SnappyHexMesh arbitary meshing

shantanumandhane · March 11, 2019, 09:59

Hello foamers,
I am facing an issue with snappyHexMesh for creating the mesh. I am getting multiple wierd/arbitary lines in the mesh and it has created tons of singular point due to which my simulation is crashing.
Please help.

Thanks in advance

shantanumandhane · March 12, 2019, 13:50

I am receiving arbitrary mesh every time I run the same sHM code.

Is it normal to observe such defects?

Also, would this mesh create further errors?

wyldckat · March 12, 2019, 19:14

Quick answer: I suspect that what you are seeing isn't real, namely that it's part of the polyhedral decomposition and not part of the original mesh. Follow the instructions given here: https://openfoamwiki.net/index.php/F...is_in_ParaView - to properly see the real mesh.

shantanumandhane · March 13, 2019, 06:53

okay! But before using sHM I created the mesh with blockMesh which was symmetric in yz-plane, then why would the refined cells come out of the plane of symmetry?

simrego · March 13, 2019, 10:37

Because there is no reason to stay in plane (only if you have a constrain), and maybe during the smoothing process the x coordinate which is 0 for example becomes 1e-10, which is still 0. Or it is just simply a numerical error since 0 is never (i know there are some cases when 0 is 0) 0 exactly when you use floating point numbers.
Or as wyldcat mentioned it is simply a visualization "error".

March 12, 2019, 19:14		#3
wyldckat Retired Super Moderator Bruno Santos Join Date: Mar 2009 Location: Lisbon, Portugal Posts: 10,981 Blog Entries: 45 Rep Power: 128	Quick answer: I suspect that what you are seeing isn't real, namely that it's part of the polyhedral decomposition and not part of the original mesh. Follow the instructions given here: https://openfoamwiki.net/index.php/F...is_in_ParaView - to properly see the real mesh. __________________ OpenFOAM: FAQ \| Getting started Forum: How to get help, to post code/output and forum guide Read this before sending me PM

March 13, 2019, 06:53		#4
shantanumandhane New Member shantanu mandhane Join Date: Jun 2018 Posts: 10 Rep Power: 8	okay! But before using sHM I created the mesh with blockMesh which was symmetric in yz-plane, then why would the refined cells come out of the plane of symmetry? __________________ Regards! Shantanu

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March 13, 2019, 10:37		#5
simrego Senior Member anonymous Join Date: Jan 2016 Posts: 416 Rep Power: 14	Because there is no reason to stay in plane (only if you have a constrain), and maybe during the smoothing process the x coordinate which is 0 for example becomes 1e-10, which is still 0. Or it is just simply a numerical error since 0 is never (i know there are some cases when 0 is 0) 0 exactly when you use floating point numbers. Or as wyldcat mentioned it is simply a visualization "error".