CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

CFD of external flow over airfoil with 3D mesh and one cell thickness

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 30, 2020, 04:49
Default CFD of external flow over airfoil with 3D mesh and one cell thickness
  #1
New Member
 
Join Date: Mar 2020
Posts: 4
Rep Power: 3
AleXX87 is on a distinguished road
Dear CFD users,


I am trying to simulate the turbulent 3D flow over a thin periodic wing element, with a 3d damage on the leading edge.

The mesh is unstructured and automatically generated by ansys meshing (for me this is a mandatory aspect). This makes the grid to have 1 cell thickness in the far field.

I have to impose a periodic BC spanwise, but this seems to have a very bad effect on the convergence for the mesh zone with one layer elements spanwise (far field). Sometimes I cannot even initialize the run.


Does anyone knows if there is any issue or particular setting that can help to solve this problem?


(I wish to not come back to the mesh and try to make two layers at least everywhere)


Thanks
AleXX87 is offline   Reply With Quote

Old   March 30, 2020, 05:16
Default One-Cell Thickness
  #2
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,946
Blog Entries: 1
Rep Power: 33
vinerm will become famous soon enough
By one-cell thickness do you mean span length? Why do you want to use one-cell thickness?
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Old   March 30, 2020, 05:21
Default
  #3
New Member
 
Join Date: Mar 2020
Posts: 4
Rep Power: 3
AleXX87 is on a distinguished road
Yes, but it is not really a choice, it is more a consequence of using the automatic meshing tool. Because of the geometry of the damage I want to simulate, I must use an unstructured tetrahedral mesh. Being the far field cells very large with respect to the spanwise thickness of the domain, the mesh tool reduces this region to a one layer cell mesh.
AleXX87 is offline   Reply With Quote

Old   March 30, 2020, 05:24
Default Unclear
  #4
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,946
Blog Entries: 1
Rep Power: 33
vinerm will become famous soon enough
Your description is not very clear to me. Could you share a picture showing what you mean by one-cell? There is nothing called automatic meshing; there are default parameter values and there are user provided values. Tet mesh is not bad but one-cell thickness anywhere is mostly useless, except under certain specific conditions.
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Old   March 30, 2020, 05:48
Default
  #5
New Member
 
Join Date: Mar 2020
Posts: 4
Rep Power: 3
AleXX87 is on a distinguished road
You can find an example attached for what I intend as one cell span. That is a view of the airfoil lower boundary. The red arrow shows the spanwise direction.

With the proper settings I can obtain a mesh with more than 1 cell spanwise in the area of the figure, but not in the far field.



I hope this helps to understand the configuration I am trying to simulate.
Attached Images
File Type: png Untitled.png (56.7 KB, 9 views)
AleXX87 is offline   Reply With Quote

Old   March 30, 2020, 05:58
Default Damage
  #6
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,946
Blog Entries: 1
Rep Power: 33
vinerm will become famous soon enough
If the shape of the damage on the airfoil is 3D, then you should generate proper 3D mesh. With one cell thickness, the simulation would essentially be 2D. I understand that meshing tool may not be doing a good job of put more cells in the far-field region but that user needs to control by using sizes or some other option. This mesh will not give you good results. I suppose someone in Meshing forum can help you with this.

If the damage is not really 3D, then use a 2D domain.
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Old   March 30, 2020, 06:05
Default
  #7
New Member
 
Join Date: Mar 2020
Posts: 4
Rep Power: 3
AleXX87 is on a distinguished road
Thank you for your reply.

Yes, the damage is 3D but is concentrated in a small region, anyway I need to solve a 3D periodic problem.
I just write here what I understood and close the topic:

Giving a mesh with one cell span in the far field region (as in the figure before) and periodic condition does not produce good results in fluent, no solver configuration can help this.

The only possible solution is to try to put at least two layers of cells between the periodic faces everywhere in the mesh (which is possible but requires more work from the definition of the geometry of the domain).
AleXX87 is offline   Reply With Quote

Old   March 30, 2020, 06:14
Default Periodicity
  #8
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,946
Blog Entries: 1
Rep Power: 33
vinerm will become famous soon enough
Do note that periodicity requires at least four cells across the thickness. With one-cell, periodicity does not mean anything, if periodicity is meant across the span length.
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Reply

Tags
airfoil, externalflow, periodic bc

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



All times are GMT -4. The time now is 23:35.