CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > ANSYS Meshing & Geometry

[ICEM] Hybrid mesh for 2D boundary layer

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

Like Tree7Likes

Reply
 
LinkBack Thread Tools Display Modes
Old   June 28, 2013, 14:19
Default
  #21
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,661
Blog Entries: 1
Rep Power: 34
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
Agreed... You should try ANSYS Meshing with patch conforming meshing if you want to get your Gambit Size function like behavior back.
__________________
-----------------------------------------
Please help guide development at ANSYS by filling in these surveys

Public ANSYS ICEM CFD Users Survey

This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)...

CFD Online Users Survey
PSYMN is offline   Reply With Quote

Old   June 28, 2013, 14:24
Default
  #22
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,902
Blog Entries: 6
Rep Power: 37
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
Dear Simon

Any plan to implement gambit tri pave and gambit size function in ICEM?
Far is offline   Reply With Quote

Old   June 29, 2013, 11:10
Default
  #23
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,661
Blog Entries: 1
Rep Power: 34
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
Sort of... It was implemented in Multizone. Multizone uses the Hexa framework, but when you have an unstructured block or paved face, it can use the gambit sizing function...

But I don't expect we will be hooking up the Gambit sizing function to the patch conforming mesher directly... Instead the direction is forward with ICEM CFD technology being hybridized with gambit (and other) technology in future products.

This is probably because users who want surface mesh to respect a sizing function can just use patch independent in ICEM CFD, which does respect the sizing function and also includes patch independence.
__________________
-----------------------------------------
Please help guide development at ANSYS by filling in these surveys

Public ANSYS ICEM CFD Users Survey

This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)...

CFD Online Users Survey
PSYMN is offline   Reply With Quote

Old   June 29, 2013, 11:20
Default
  #24
Member
 
sadjad.s's Avatar
 
sadjad
Join Date: Jan 2012
Posts: 57
Rep Power: 5
sadjad.s is on a distinguished road
Send a message via Yahoo to sadjad.s
Quote:
Originally Posted by PSYMN View Post
This is probably because users who want surface mesh to respect a sizing function can just use patch independent in ICEM CFD, which does respect the sizing function and also includes patch independence.
Hi Simon,
By "Size function" you mean Curvature/Proximity Based Refinement?
__________________
ICEM, CFX and Fluent expert
sadjad.s is offline   Reply With Quote

Old   June 29, 2013, 11:22
Default
  #25
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,661
Blog Entries: 1
Rep Power: 34
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
Quote:
Originally Posted by sadjad.s View Post
Hi Simon,
By "Size function" you mean Curvature/Proximity Based Refinement?
Yes, that is the ICEM CFD size function. It works with patch independent tetra and surface mesh.
__________________
-----------------------------------------
Please help guide development at ANSYS by filling in these surveys

Public ANSYS ICEM CFD Users Survey

This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)...

CFD Online Users Survey
PSYMN is offline   Reply With Quote

Old   June 29, 2013, 11:25
Default Question
  #26
Member
 
sadjad.s's Avatar
 
sadjad
Join Date: Jan 2012
Posts: 57
Rep Power: 5
sadjad.s is on a distinguished road
Send a message via Yahoo to sadjad.s
But it is different with Gambit Size Function except for name.
__________________
ICEM, CFX and Fluent expert
sadjad.s is offline   Reply With Quote

Old   June 29, 2013, 11:47
Default
  #27
Senior Member
 
PSYMN's Avatar
 
Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,661
Blog Entries: 1
Rep Power: 34
PSYMN has a spectacular aura aboutPSYMN has a spectacular aura about
Yes, the ICEM CFD and Gambit Sizing functions are different code, independently developed, but for the same purpose.

TO me, the main difference is that the ICEM CFD tetra mesh is octree, and the mesh actually shows the sizing function directly. With Gambit, they actually run a size function controlled octree in the background and then use that to indirectly guide the patch conforming and delaunay mesh generation.

So the difference is less about the size functions and more about how the mesh uses the size function.
__________________
-----------------------------------------
Please help guide development at ANSYS by filling in these surveys

Public ANSYS ICEM CFD Users Survey

This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)...

CFD Online Users Survey
PSYMN is offline   Reply With Quote

Old   June 29, 2013, 11:57
Default
  #28
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,902
Blog Entries: 6
Rep Power: 37
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
But the gambit mesh stick (and more uniform) more to surface as compared to ICEM even though they are also using octree, denauly etc. e.g. mesh on high aspect ratio wing

Quote:
TO me, the main difference is that the ICEM CFD tetra mesh is octree, and the mesh actually shows the sizing function directly. With Gambit, they actually run a size function controlled octree in the background and then use that to indirectly guide the patch conforming and delaunay mesh generation.
What is differnce between size function controlled octree and octree with size function?
I thought gambit needs the surfaces mesh first and that is patch conforming (as gambit is bottom up mesher).

When it uses dalaunay mesher?
Far is offline   Reply With Quote

Old   June 29, 2013, 12:38
Default
  #29
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,902
Blog Entries: 6
Rep Power: 37
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
Ok. Here is full tutorial on hybrid 2d meshing in ICEM CFD. Everything is attached with post. Hope you will like it.

https://dl.dropboxusercontent.com/u/..._2dairfoil.rar
sadjad.s, fedefrance and Bachduong like this.
Far is offline   Reply With Quote

Old   June 29, 2013, 14:24
Default explanation
  #30
Member
 
sadjad.s's Avatar
 
sadjad
Join Date: Jan 2012
Posts: 57
Rep Power: 5
sadjad.s is on a distinguished road
Send a message via Yahoo to sadjad.s
Quote:
TO me, the main difference is that the ICEM CFD tetra mesh is octree, and the mesh actually shows the sizing function directly. With Gambit, they actually run a size function controlled octree in the background and then use that to indirectly guide the patch conforming and delaunay mesh generation.
I think this post of Simon totally explains what Gambit does in Size function.
But the point is in 3D cases, with a little more job, by making nested densities we can get that size function. And it is actually just similar to what we get in gambit.

Quote:
Ok. Here is full tutorial on hybrid 2d meshing in ICEM CFD. Everything is attached with post. Hope you will like it.
I would donate if I could due to these free and complete tutorials. Thank you.
Bachduong likes this.
__________________
ICEM, CFX and Fluent expert
sadjad.s is offline   Reply With Quote

Old   June 29, 2013, 14:36
Default
  #31
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,902
Blog Entries: 6
Rep Power: 37
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
Quote:
But the point is in 3D cases, with a little more job, by making nested densities we can get that size function. And it is actually just similar to what we get in gambit.
Thats the whole point. one of my friend is making surface mesh in gambit with very good and nice looking surface mesh in gambit with size function and also volume mesh with size function. The mesh density is very much fine where they want and mesh is much more uniform.

And then they take it to icem where they create geometry and insert 3d prism layers which is almost impossible in Gambit.

What I feel is that with ICEM Octree and patch independent surface mesh you can mesh a very complex geometry within few hours while in gmaibt you need detailed working in defining size functions for edges, surfaces and volumes. Sizing on each edge. Still Gambit has difficulty in making volume mesh. Moreover it does not support heavy meshes and hangs often.

Only requirement of ICEM is that you should know the appropriate settings for your model which I find some times difficult to get in first place.
Far is offline   Reply With Quote

Old   June 29, 2013, 14:42
Default
  #32
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,902
Blog Entries: 6
Rep Power: 37
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
Quote:
I would donate if I could due to these free and complete tutorials. Thank you.
I should have said that, this tutorial is based on instructions by Simon
Far is offline   Reply With Quote

Old   January 9, 2014, 11:26
Default
  #33
New Member
 
Join Date: Jun 2013
Posts: 16
Rep Power: 3
kozalp is on a distinguished road
Quote:
Originally Posted by Mmc View Post
Hi Andrea,
How did you manage to create the region of the boundary layer by scaling the airfoil in icem? I have tried geometry/transform geometry/scale but the created curve is not satisfactory, it does not create a "parallel" airfoil with constant distance from the original airfoil.
Thanks,
Manuel
Hey Manuel,

Since your curve has a varying slope, you can't have a perfect boundary layer jus by scaling. If you look carefully the boundary layer which Andrea did, the distance between BL and geometry varies.
You can have a fine BL by scaling with different x and y offset coefficients.

If you want a perfect BL, you can do it following this steps:

1) You should know the equation of your curve or at least coordinates of points.
2) Then you can find slopes at given points by taking the first derivative of your curve equation or numerically deriving by using points.
3) Then calculate your max boundary layer thickness by using BL equation.
4) Find the points which will lay on your boundary curve by using the slope at each point and BL thickness.

I did it in excel. It takes time but, for me it was the only way to do it.
fedefrance likes this.

Last edited by kozalp; January 9, 2014 at 11:28. Reason: corrected a writing error
kozalp 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
[ANSYS Meshing] Creating Hex Boundary Layer Mesh and Unstructured everywhere else NLao ANSYS Meshing & Geometry 1 March 15, 2011 08:35
Not able to mesh a helix with boundary layer using gambit rohitjvbibin Main CFD Forum 0 March 5, 2011 12:28
Not able to mesh a helix with boundary layer using gambit rohitjvbibin ANSYS 0 March 5, 2011 12:27
Dynamic Mesh with Boundary Layer Marcell FLUENT 0 March 11, 2009 10:40
errors Fahad Main CFD Forum 0 March 23, 2004 14:20


All times are GMT -4. The time now is 17:07.