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

[ANSYS Meshing] mesh-indep. study (!pics inside!)

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 8, 2013, 04:05
Default mesh-indep. study (!pics inside!)
  #1
m4D
New Member
 
Join Date: Sep 2012
Posts: 8
Rep Power: 13
m4D is on a distinguished road
Hello. I'm trying to mesh (ansys mesher) an axial turbine (a flow inside it) here:
(yellow = hub, red = blade, external cylinder side = shroud)



As far as i get it, i must perform a mesh-independence study to be sure the output is correct. When i make the mesh finer (increasing relevance), i got the following (presrise - output parameter - outlet to inlet pump pressure rise):


The mesh is created automatically with ASF "On Curvature"/"Prox. + curv." + tried adding inflation of blade,hub,shroud - similar results. Approx. number of elements: from 400k to 800k.

The question is: is the auto-generated mesh so bad (it doesn't "converge" to any result value (presrise), while i make it finer) , or i'm just doing it wrong? Thanks in advance.
Attached Images
File Type: jpg 1.JPG (12.3 KB, 35 views)
File Type: jpg 2.JPG (18.5 KB, 34 views)
File Type: jpg 3.jpg (95.0 KB, 35 views)
File Type: jpg 4.jpg (102.3 KB, 34 views)
m4D is offline   Reply With Quote

Old   February 8, 2013, 05:20
Default
  #2
Super Moderator
 
flotus1's Avatar
 
Alex
Join Date: Jun 2012
Location: Germany
Posts: 3,396
Rep Power: 46
flotus1 has a spectacular aura aboutflotus1 has a spectacular aura about
Refining only a part of the mesh in a complex geometry or using the somewhat arbitrary "relevance" function in the Ansys mesher can not lead to the type of convergence you expect.

Usually when checking for mesh dependence, the variable is plotted against the cell size.
In general, with complex turbulent flows the convergence with cell size does not need to be monotonic.
When refining the mesh, details of the flow field resolved only on fine meshes affect the flow field at other places, leading to non-monotonic convergence.
flotus1 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
3D Hybrid Mesh Errors DarrenC ANSYS Meshing & Geometry 11 August 5, 2013 07:42
[ANSYS Meshing] Grid refinement for mesh independency study peterputer ANSYS Meshing & Geometry 5 July 26, 2012 10:39
[snappyHexMesh] non-smooth mesh Svensson OpenFOAM Meshing & Mesh Conversion 11 January 18, 2012 10:13
[ANSYS Meshing] avoid to mesh the inside of the blade swiss_zhang ANSYS Meshing & Geometry 1 June 9, 2011 08:37
[snappyHexMesh] external flow with snappyHexMesh chelvistero OpenFOAM Meshing & Mesh Conversion 11 January 15, 2010 20:43


All times are GMT -4. The time now is 09:27.