CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > Siemens > STAR-CCM+

Questions about Polyhedral and Prism layer meshing

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 9, 2016, 02:36
Default Questions about Polyhedral and Prism layer meshing
  #1
Member
 
B.H.
Join Date: Nov 2014
Location: PA, USA
Posts: 47
Rep Power: 8
niablis is on a distinguished road
I have created a polyhedral volume mesh that grows off of a prism layer attached to a surface. I believe have three issues currently. For those of you interested, here is the Star-CCM+ case file in google drive. Just FYI, its about 4 GB.

First, my polyhedral volume mesh has an ordered series of low quality cells. It almost seems as if the low quality cells were generated when the mesh was subdividing, but that is really just a guess. I have the polyhedral mesher selected with 1 Optimization cycle, and a quality threshold of 1. I'm not sure if this makes a difference, but I also am using a volumetric control the cell size in the entire volume, just like I'm doing to refine the wake region. Maybe the using the volumetric control leads to these low quality cells?




In this next image, I have set my viewing threshold to a quality less that 0.2.



Here is a top down shot. You can see that there is the same structure throughout the entire volume. The darker sections are where volumetric control is active, reducing the cell size.





Second, in some locations, my volume mesh and my BL prism mesh seem to occupy the same space. It seems to occur when my cell size is under a certain threshold.



Here is a view showing the prism layer without the merging volume mesh.




Third, despite my best attempts, my BL prism layer quality is hit and miss. In some spots, it seems to regard curves and in others it doesn't. Some times it seems to randomly shrink in thickness. As it approaches the trailing edge of my flaps, the prism layer ends and then reappears on the trailing edge.

Prism layer projected on the cut plane and also onto the side of the step.



This image shows areas where the prism layer shrinks.



Prism layer at the trailing edge




I really appreciate any and all advice you may have on any of the three topics.

Cheers!
Attached Images
File Type: jpg Low quality volume cells near field.jpg (185.9 KB, 82 views)
File Type: jpg Low quality volume cells highlighted near field.jpg (192.1 KB, 75 views)
File Type: jpg Low quality volume cells top down.jpg (82.5 KB, 63 views)
File Type: jpg BL and volume mesh merge.jpg (133.5 KB, 70 views)
File Type: jpg BL and volume mesh merge 2.jpg (195.5 KB, 70 views)

Last edited by niablis; September 9, 2016 at 02:41. Reason: attached pictures too
niablis is offline   Reply With Quote

Old   September 9, 2016, 02:43
Default
  #2
Member
 
B.H.
Join Date: Nov 2014
Location: PA, USA
Posts: 47
Rep Power: 8
niablis is on a distinguished road
Attaching more images
Attached Images
File Type: jpg BL slot wave pattern.jpg (164.2 KB, 51 views)
File Type: jpg BL slot and cut plane close up.jpg (154.1 KB, 52 views)
File Type: jpg BL at the TE.jpg (98.7 KB, 52 views)
niablis is offline   Reply With Quote

Old   September 22, 2016, 21:29
Default
  #3
Senior Member
 
Join Date: Nov 2010
Location: USA
Posts: 1,230
Rep Power: 21
me3840 is on a distinguished road
Your prisms have trouble growing over tight corners because the mesh shrinks in size far too rapidly and your prism height is too large. Growing large prisms over small features like this is not robust, you need to either lower the prism size with a custom control or modify the prism layer min thickness percentage and the layer reduction percentage. Look for them in the user guide.

I would leave the quality settings at the default for a simple geometry like this.

Those partitions you see are probably there because you're meshing in parallel? It looks like a bug, I would disable it.

You also need to modify the volumetric blending factor, your volume control is too harsh of a stencil.
me3840 is offline   Reply With Quote

Old   September 23, 2016, 01:32
Default
  #4
Member
 
B.H.
Join Date: Nov 2014
Location: PA, USA
Posts: 47
Rep Power: 8
niablis is on a distinguished road
me3840, thanks for your insight and advice!! Is the parallel meshing bug a known problem?
niablis 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
Prism Layers issue for Model replicating Abaqus Co-Sim Mechanical Coupling Tutorial MTabone STAR-CCM+ 4 April 14, 2015 03:28
Issues with prism layers around a Wind Turbine Field85 STAR-CCM+ 1 September 23, 2014 23:42
No prism layer mesh is generated, I don't know why... capikrad STAR-CCM+ 6 April 25, 2014 06:06
Polyhedral Mesh Quality in Star-CCM+ niazaliahmed STAR-CCM+ 3 March 8, 2012 14:51


All times are GMT -4. The time now is 23:25.