CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Mesh Utilities

About OpenFOAM and concave faces or cells

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

Like Tree1Likes
  • 1 Post By eugene

Reply
 
LinkBack Thread Tools Display Modes
Old   January 30, 2009, 01:49
Default Hello, I am looking for som
  #1
Senior Member
 
Martin Beaudoin
Join Date: Mar 2009
Posts: 330
Rep Power: 13
mbeaudoin will become famous soon enough
Hello,

I am looking for some experienced opinions about OpenFOAM and the presence of concave faces or concave poly cells in OF meshes.

What are the major problems or major side effects related to the presence of concave cells/faces/polygons in OpenFOAM meshes, if any?

Are there any known solver numerical issues related to the presence of concave cells or faces in OF meshes?

snappyHexMesh seems to allow face concavity angles of up to 80 degrees by default. This seems like quite a large value.
In general, how will lowering the value of this parameter called maxConcave in snappyHexMeshDict affect the overall mesh quality?
Any rule of thumb?

With snappyHexMesh, is it possible to generate good quality meshes without the presence of any concave cells in the final output (using maxConcave < 0)?

Finally, checkMesh will only report the presence concave faces in a mesh if the face concave angle is greater than 10 degree.
This 10 degree value is hard-coded in the file checkMesh/checkGeometry.C
Wouldn't it be useful to have this angle value specified through a controlDict switch instead, so that checkMesh could report the presence ALL concave faces?

Thank you in advance for helping me get a better understanding of these issues.

Martin
mbeaudoin is offline   Reply With Quote

Old   January 30, 2009, 07:39
Default Cell concavity is not really r
  #2
Senior Member
 
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 12
eugene is on a distinguished road
Cell concavity is not really relevant in a face based mesh, in any case, this concavity parameter refers to face concavity and not cell concavity.

Face concavity does not mean the cell is concave. This is the edge angle between adjacent edges in a face, not between adjacent faces. This property does not influence the discretisation directly. The most important factors for this are:
-non-orthogonality
-volume Ratio
-delta ratio
-skewness

Although extreme instances of all the other criteria can cause problems too (otherwise we wouldn't need them), especially when face areas tend to zero.

Lowering the maxConcave value will "improve" the cell quality, but the mesh might not conform as well to the surface as what might otherwise be the case.
maryCFD likes this.
eugene is offline   Reply With Quote

Old   March 29, 2015, 07:53
Default
  #3
New Member
 
Stefan
Join Date: Jan 2011
Location: Bremen
Posts: 20
Rep Power: 6
holodeck10 is on a distinguished road
as an addition:

checkMesh -allGeometry

would write all concave cells into a set.
holodeck10 is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Extension of fluentMeshToFoam internal cells and faces gschaider OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 34 January 2, 2011 11:01
selection of individual cells (not cell faces) kamal CD-adapco 0 January 17, 2008 02:00
Finding neighbouring cells when looping over faces in faceSet olwi OpenFOAM Running, Solving & CFD 2 December 13, 2007 09:03
Mesh to points cells faces and boundaries files billy OpenFOAM Pre-Processing 19 April 18, 2006 15:38
Beginner: cell faces of surface cells Sunlight007 CD-adapco 0 August 24, 2003 17:19


All times are GMT -4. The time now is 23:01.