CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Meshing & Mesh Conversion

[snappyHexMesh] SHM not snapping on simple case

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 4, 2018, 12:19
Default SHM not snapping on simple case
  #1
New Member
 
Join Date: Mar 2016
Posts: 11
Rep Power: 10
slaners is on a distinguished road
Hello ,

I am trying to simulate a channel with pins inside. I defined the pins with searchable cylinders. SHM creates the castellated mesh. However, when it comes to snapping, SHM does not snap surfaces of the pins.
I attached a simple version of the geometry (using one pin for the moment to solve this issue).

Thank you in advance for your help !
Attached Files
File Type: txt snappyHexMeshDict.txt (10.6 KB, 10 views)
File Type: txt blockMeshDict.txt (1.8 KB, 7 views)
slaners is offline   Reply With Quote

Old   June 5, 2018, 04:24
Default
  #2
Senior Member
 
anonymous
Join Date: Jan 2016
Posts: 416
Rep Power: 14
simrego is on a distinguished road
Hi!

This 10.0 tolerance is pretty huge, you can leave it on the default 2.0 or somewhere between 1.2 and 2.0.
Do you resolve the surfaces sufficiently? Can you attach an image?

A guess: For me the implicitSurfaceSnap usually results badly snapped edges, and even if it can snap, the quality of my mesh is poor. Try to use explicitFeatureSnap.
simrego is offline   Reply With Quote

Old   June 5, 2018, 10:04
Default
  #3
New Member
 
Join Date: Mar 2016
Posts: 11
Rep Power: 10
slaners is on a distinguished road
Thanks for the answer simrego,
I changed the tolerance but it did not have any influence on the final mesh. I added a snapshot of a z-normal slice in the mesh. As you can see, the mesh is castellated and there was no snapping on the pin. Any thoughts ?
Attached Images
File Type: jpg Mesh_global.jpg (66.5 KB, 37 views)
File Type: jpg Mesh_pin.jpg (112.9 KB, 46 views)
slaners is offline   Reply With Quote

Old   June 5, 2018, 10:08
Default
  #4
Senior Member
 
anonymous
Join Date: Jan 2016
Posts: 416
Rep Power: 14
simrego is on a distinguished road
Wow. That's the snapped one? Nice.

You ran with snappyHexMesh -overwrite? If not, check the other time directories.
Have you got any warnings in the log?
simrego is offline   Reply With Quote

Old   June 5, 2018, 10:24
Default
  #5
New Member
 
Join Date: Mar 2016
Posts: 11
Rep Power: 10
slaners is on a distinguished road
Yeah it is. I did use -overwrite.
I have one warning :

"FOAM Warning : Displacement (-1.620465057e-08 0 0) at mesh point 1503539 coord (-0.004444983795 -0.003175 1.257804343e-05) points through the surrounding patch faces"

But the most concerning one is :

" faces with face pyramid volume < 1e-13 : 1542251 "

Even with more cells, I still get this castellated kind of mesh and there seem to be no snapping on the cylinder surface.
slaners is offline   Reply With Quote

Old   June 5, 2018, 16:30
Default
  #6
Senior Member
 
anonymous
Join Date: Jan 2016
Posts: 416
Rep Power: 14
simrego is on a distinguished road
Hi!


I tried your dicts and works perfectly for me. But you should increase the number of the elements in the x direction (i tried with 120), and then you should have something like the attached image.
I tried it with OpenFOAM 4.0.
Attached Images
File Type: png Screenshot from 2018-06-05 21-27-40.png (11.7 KB, 39 views)
simrego is offline   Reply With Quote

Old   June 6, 2018, 06:52
Default
  #7
New Member
 
Join Date: Mar 2016
Posts: 11
Rep Power: 10
slaners is on a distinguished road
Hi simrego !

Thanks for the answer. You're right, the correct mesh is in another time folder !
Do you also have the "faces with face pyramid volume < 1e-13" issue ?
slaners is offline   Reply With Quote

Old   June 6, 2018, 07:43
Default
  #8
Senior Member
 
anonymous
Join Date: Jan 2016
Posts: 416
Rep Power: 14
simrego is on a distinguished road
Run snappyHexMesh as:
snappyHexMesh -overwrite
and you will have the final mesh in the constant time (0).

Yes i have. Honestly i don't know the real reason for that, but with implicitFeatureSnap I usually have many of these bad faces. Maybe you can still use this mesh. But with explicitFeatureSnap I usually get rid of these errors.
I hope some professional SHM user could explain this error.
simrego is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Problems with an apparently simple case HHOS OpenFOAM Running, Solving & CFD 0 September 11, 2013 04:50
[snappyHexMesh] SHM not snapping marupio OpenFOAM Meshing & Mesh Conversion 7 January 23, 2013 22:28
[snappyHexMesh] SHM: feature edge snapping not conforming thab OpenFOAM Meshing & Mesh Conversion 3 November 26, 2012 15:04
Help Required With Simple Test Case steph79 OpenFOAM Pre-Processing 4 August 3, 2010 08:45
Simple Q. How to complete a Case? W.A. Siemens 3 April 23, 2006 20:41


All times are GMT -4. The time now is 09:31.