CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

Problem using AMI

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

Like Tree31Likes

Reply
 
LinkBack Thread Tools Display Modes
Old   February 5, 2014, 14:28
Default
  #201
Senior Member
 
linnemann's Avatar
 
Niels Nielsen
Join Date: Mar 2009
Location: NJ - Denmark
Posts: 472
Rep Power: 16
linnemann will become famous soon enough
Hi.

Please share with dropbox/gDrive etc.

I'm sure there is a simple solution.
__________________
Linnemann

PS. I do not do personal support, so please post in the forums.
linnemann is offline   Reply With Quote

Old   February 5, 2014, 16:07
Post
  #202
Member
 
arash mahboubi
Join Date: Jun 2013
Location: Iran
Posts: 40
Rep Power: 5
arashfluid is on a distinguished road
Send a message via Yahoo to arashfluid
Thanks Friends,
Problem is solved.Now rotor moves properly.
My main problem is too much run time.This is why I got into the AMI.
If using the AMI ,can be used both of fixed topology and changing topology mesh manipulation models in dynamicMeshDict?
What is your opinion about reducing the run time?
arashfluid is offline   Reply With Quote

Old   April 26, 2014, 15:14
Default
  #203
New Member
 
Stefano Gaggero
Join Date: Mar 2013
Posts: 19
Rep Power: 5
Mashiro5 is on a distinguished road
Dear All,


I'm working on the same topic (mainly a propeller rotating and interacting with a rudder) and I would like to share my knowledge and ask for some problems I'm having.

I succesfully run the propeller tutorial and I set up my case with a slightly complicated propeller geometry. The snap stage worked well up to snappyng. At that stage the AMI weights were abt. 0.8 1.2 1.0001 and if I run this case, eithout the addition of prism layers, everything works fine.

When I add prismlayers in snappyhexmesh (I found that the propeller tutorial case neglects prism layer addition) the resulting mesh, due to the layers addition itself, is slightly different also close to the interface and, there, shows some "deformations" (in particular for only one of the two interfaces patch) and "holes" (if seen using cutting planes). The resulting AMI min weight falls very close to 0 and the simulations stop after a while, when in correspondance of a particular time step, min AMI wheigh becomes 0.

Do you have any sugestions on how to prevent the modification of the mesh at the interfaces during the layer addition?

Many Thanks,

Stefano
Mashiro5 is offline   Reply With Quote

Old   April 26, 2014, 17:03
Default
  #204
Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 9,531
Blog Entries: 36
Rep Power: 97
wyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nice
Greetings Stefano,

Quote:
Originally Posted by Mashiro5 View Post
Do you have any sugestions on how to prevent the modification of the mesh at the interfaces during the layer addition?
Without any more information (images and/or example case), the best I can do is suggest that you read+study the tutorials listed here: http://openfoamwiki.net/index.php/Sn...als_and_Guides

In addition, if you don't have experience using snappyHexMesh for adding layers, then you should use a small test case and test out the settings explained in the tutorials.

Best regards,
Bruno
__________________
___
I'll be at OFW11 in Portugal
wyldckat is offline   Reply With Quote

Old   April 27, 2014, 08:12
Default
  #205
New Member
 
Stefano Gaggero
Join Date: Mar 2013
Posts: 19
Rep Power: 5
Mashiro5 is on a distinguished road
Dear Bruno, as usual you are right.. an appropriate image can explain better than hundreds of words.

I have a reasonable experience with snappyHexMesh (I already read the tutorial you suggested) and I usually use snappy to mesh propellers and ship hulls with satisfactory results, of course adding also boundary layers.

Now I'm trying to model the propeller operating behind the hull. The snap works well, as you can see in the image. The innerCylinder and the innerCylinder_slave have almost the same surface mesh, with well defined edges, even without an explicit refinement. If I start my simulation without the layer addition everything works fine: the AMI weights are well above 0 (abt. 0.8 - 1.2 - 1.0000x). During the simulation especially the min value oscillates but never comes below 0.5.

When instead I include, in the mesh generation, also the prism layer, something goes wrong with the mesh. As from the figure the layers are well added to the hull (and also to the propeller) surface even if the relativeSize option produces a variably prims layer thickness (but at thip point this is not important). The layer addition, unfortunately, changes the mesh arrangement and in particular change the mesh near the edges of the interface, only from the innerCylinder_slave point of view. This tooth-shape is responsible of very low values of the min AMI weight, abt 0.0006. The simulation starts but, in correspondence of certain angular positions the minimum weight becomes 0 and openFoam stops.

I tried different mesh arrangements, decreasing the size of the mesh in correspondance of the interface, clustering cells on its the edges (that are properly marked used eMesh files), changing a bit the parameters of the layer addition process. Everything is ok up to the snap stage. After the layer addition the AMI weight tremendously falls...

Now I'm wondering if it is more appropriate to create separately the two meshes and finally merge them, but after a week of "try and error" I'm looking for some feedback or, at least, consolations...
Attached Images
File Type: jpg snap.jpg (96.2 KB, 97 views)
Mashiro5 is offline   Reply With Quote

Old   May 1, 2014, 09:07
Default
  #206
Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 9,531
Blog Entries: 36
Rep Power: 97
wyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nice
Hi Stefano,

For better or for worse, the image attachment system here on the forum will automatically rescale the images to a size that will (hopefully) be less than 100kB. This means that the image you provided doesn't have enough resolution to see all of the details

Although from what I can see, the mesh without layers isn't exactly perfect, or perhaps it was the JPG image compressor that added an artifact to the image...
Anyway, I don't have enough experience with adding layers in snappyHexMesh, so the best I can do is to suggest that you share an example case that reproduces this same problem. In addition, knowing which OpenFOAM version you're using would help.
A good meshing base case would be the tutorial "compressible/rhoPimpleDyMFoam/annularThermalMixer", which is available at least in OpenFOAM 2.3.

Best regards,
Bruno
__________________
___
I'll be at OFW11 in Portugal
wyldckat is offline   Reply With Quote

Old   July 23, 2014, 12:45
Default cfMesh with AMI
  #207
Member
 
Christian
Join Date: Apr 2014
Posts: 69
Rep Power: 4
crixman is on a distinguished road
Hi all,
did anyone tried to run an AMI simulation using cfMesh?
How would you go into that?
I'm not sure if I have to make two geometries for inner and stator, mesh them separately and combine them, or if I just need a single stl file with all patches.
How would I make the rotating cellZone then?
crixman is offline   Reply With Quote

Old   October 10, 2014, 01:58
Default
  #208
Member
 
Abhijit
Join Date: Jul 2014
Posts: 75
Rep Power: 3
Jetfire is on a distinguished road
Dear all

Can someone please explain the difference between baffles and patches, for simulations using AMI do we need to create patches for the AMI interfaces or baffles i am confused.
Jetfire is offline   Reply With Quote

Old   October 11, 2014, 13:53
Default
  #209
Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 9,531
Blog Entries: 36
Rep Power: 97
wyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nice
Greetings to all!

@crixman:
Quote:
Originally Posted by crixman View Post
did anyone tried to run an AMI simulation using cfMesh?
Sorry for the very late reply. The answer is simple:
  1. Create the meshes separately.
  2. Merge meshes, no stitching required. Have a look at this post of mine: Problem using AMI post #184

Quote:
Originally Posted by Jetfire View Post
Can someone please explain the difference between baffles and patches, for simulations using AMI do we need to create patches for the AMI interfaces or baffles i am confused.
Again, have a look at this post of mine: Problem using AMI post #184

As for baffles vs patches... mmm, it's best to use the description given here: http://www.openfoam.org/version2.2.0/meshing.php
Quote:
The createBaffles utility creates zero-thickness baffles by converting internal mesh faces into (pairs of co-located) boundary faces.
In other words, baffles can only be composed of faces that belong to 2 or more cells. Patches on the other hand are usually for faces that belong to only one cell.

Best regards,
Bruno
Jetfire likes this.
__________________
___
I'll be at OFW11 in Portugal
wyldckat is offline   Reply With Quote

Old   October 13, 2014, 01:16
Default
  #210
Member
 
Abhijit
Join Date: Jul 2014
Posts: 75
Rep Power: 3
Jetfire is on a distinguished road
@wyldckat
Thanks for your reply.

Can you please help me with my simulation
My task is to simulate compressor stage of a turbocharger.
My first question:
Code:
Can we simulate these kind of turbomachinery simulations using OpenFOAM v2.3.0 with rhoPimpleDyMFoam using AMI Approach?
I have 3 separate meshes generated using ANSYS ICEM CFD
1.Inlet
2.Volute&Outlet
3.Compressor Domain

Should i import these mesh files separately to openfoam and then use mergeMeshes? or merge 1. and 2. making it a stationary mesh using ansys and 3. will be rotating mesh and import these two mesh files to openfoam? please suggest me with a strategy

And for performing rotation using AMI for this simulation how do i define the AMI interfaces. should i enclose my compressor domain with a cylinder similar to the propeller case? I'm stuck with this for months , please help me

Thank you
Jetfire is offline   Reply With Quote

Old   October 14, 2014, 10:35
Default
  #211
Senior Member
 
stephane sanchi
Join Date: Mar 2009
Posts: 300
Rep Power: 10
openfoam_user is on a distinguished road
Hi,

the following computation was done with ICEMCFD Hexa meshes (OpenFOAM 2.2.x).

https://www.youtube.com/watch?v=HJ2s...cn5Tt-X_CqxshQ

Take care at the interface between the 2 meshes. Same cell length is better.
Sometimes computations can crash with too fine grids. So it's better to begin with coarse grids as in the propeller tutorial.

Best regards,
Stéphane.
openfoam_user is offline   Reply With Quote

Old   January 16, 2015, 06:03
Default
  #212
Member
 
vincent
Join Date: Apr 2011
Posts: 41
Rep Power: 7
vince_44 is on a distinguished road
Dear All

I test with success the propeller tutorial. Now I test with my own geometry, a rotor from a water jet. The case work well but as you can see in the pictures attached, the flow is not really impacted by the rotor rotation.

Any idea?

Best regards
Attached Images
File Type: jpg rotor_pathline_01.jpg (63.1 KB, 40 views)
File Type: jpg rotor_U_isoQ.jpg (28.9 KB, 37 views)
vince_44 is offline   Reply With Quote

Old   January 16, 2015, 13:16
Default
  #213
Senior Member
 
Alhasan's Avatar
 
Hasan K.J.
Join Date: Dec 2011
Location: Bristol, United Kingdom
Posts: 196
Rep Power: 6
Alhasan is on a distinguished road
Hey,
Vincent can you please be much more clear with your question. what do you mean by 'not really impacted' ? the propellor is not moving like how you expect it to move..? maybe the velocity is not fast enough..?

Regards,
Hasan K.J
__________________
"Real knowledge is to know the extent of one's ignorance." - Confucius
Alhasan is offline   Reply With Quote

Old   January 19, 2015, 10:10
Default
  #214
Member
 
vincent
Join Date: Apr 2011
Posts: 41
Rep Power: 7
vince_44 is on a distinguished road
Hey Hasan

Sorry if I was not clear. In fact, the rotor move as I expected. But the flow seem no rotate. I attached two picture. The first is the OF calcul and the second it's with an another CFD code. The conditions are Uinlet=3.5m/s et rotation 2500rpm.

Regards
Vincent
Attached Images
File Type: jpg rotor_pathline_01.jpg (63.1 KB, 16 views)
File Type: jpg rotor_stator.jpg (43.3 KB, 30 views)
vince_44 is offline   Reply With Quote

Old   January 19, 2015, 15:40
Default
  #215
Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 9,531
Blog Entries: 36
Rep Power: 97
wyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nice
Greetings to all!

@Vincent:
Quote:
Originally Posted by vince_44 View Post
The conditions are Uinlet=3.5m/s et rotation 2500rpm.
Some years ago I learned something very important with OpenFOAM: Never assume things work the way we "think" they should.
In other words: please provide proof as to how you defined those values, namely provide the files where you configured those values.
Also, run checkMesh and confirm what dimensions your mesh has got (please provide the output from checkMesh, for us to see as well). And please indicate which OpenFOAM version you're using.

In addition, please follow the instructions given here: How to give enough info to get help

Best regards,
Bruno

Last edited by wyldckat; January 21, 2015 at 16:54. Reason: had forgotten to add any smilies...
wyldckat is offline   Reply With Quote

Old   January 22, 2015, 11:39
Default
  #216
Member
 
vincent
Join Date: Apr 2011
Posts: 41
Rep Power: 7
vince_44 is on a distinguished road
P { margin-bottom: 0.21cm; } Dear Bruno and Hasan


I use pimpleDyMFoam (OpenFOAM 2.3) to simulate the flow around a rotor. The final goal is to calculate the water jet thrust. For the moment, I test pimpleDyMFoam only with the rotor. I adapt the propeller tutorial to my problem.


I have some questions :


-When I create the patch for AMI, I feel I make a mistake (I join the log). Indeed, it read 0 faces from faceSet inletFaces and 0 faces from faceSet outletFaces


-After run the calculation, when I view the flow around the rotor, it's like if the flow don't swirl


-Finally, in my last test, I expected Fpx=-450N and I have Fpx=-1700N


I hope, I'm more clear with my problem now. In the next post, I join another files



Best regards
Attached Images
File Type: jpg mesh_rotor_01.jpg (74.7 KB, 18 views)
File Type: jpg mesh_rotor_02.jpg (73.6 KB, 22 views)
Attached Files
File Type: txt createPatch_log.txt (2.4 KB, 6 views)
File Type: txt Mesh_log.txt (3.7 KB, 4 views)
vince_44 is offline   Reply With Quote

Old   January 22, 2015, 11:43
Default
  #217
Member
 
vincent
Join Date: Apr 2011
Posts: 41
Rep Power: 7
vince_44 is on a distinguished road
Here the blockMest, SnappyHexMesh, topoSetDict and createPatchDict.

Best regards
Vince
Attached Images
File Type: jpg wj_rotor_pahtline.0135.jpg (43.1 KB, 25 views)
Attached Files
File Type: txt blockMeshDict.txt (1.7 KB, 4 views)
File Type: txt createInletOutletSets.topoSetDict.txt (1.9 KB, 8 views)
File Type: txt createPatchDict.txt (2.0 KB, 7 views)
File Type: txt snappyHexMeshDict.txt (10.9 KB, 7 views)
vince_44 is offline   Reply With Quote

Old   January 22, 2015, 12:43
Default
  #218
New Member
 
Stefano Gaggero
Join Date: Mar 2013
Posts: 19
Rep Power: 5
Mashiro5 is on a distinguished road
If you are not going to include a non-homogeneous inflow in teh stationary block or you're not interested in the initial transient (only steady state condition under investigation) a more computational efficient simulation using simpleFoam and appropriate fvOptions will be a better choice... :-)
Mashiro5 is offline   Reply With Quote

Old   January 24, 2015, 15:34
Default
  #219
Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 9,531
Blog Entries: 36
Rep Power: 97
wyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nicewyldckat is just really nice
Greetings to all!

@Vincent: Stefano might be right here.

But the problem I'm worried about the most is that you did not provide the most important file of all, which was the one I was sort-of requesting, namely the file "constant/dynamicMeshDict". This is where you are meant to properly define the value or rotation.

Best regards,
Bruno
wyldckat is offline   Reply With Quote

Old   January 26, 2015, 04:52
Default
  #220
Member
 
vincent
Join Date: Apr 2011
Posts: 41
Rep Power: 7
vince_44 is on a distinguished road
Hey Bruno and Stefano

Thanks for your answer.

Indeed, I forgot to join the dynamicMeshDict. Sorry. Now I join this file.

Best regards

Vincent
Attached Files
File Type: txt dynamicMeshDict.txt (1.2 KB, 15 views)
vince_44 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
UDF compiling problem Wouter Fluent UDF and Scheme Programming 6 June 6, 2012 04:43
Gambit - meshing over airfoil wrapping (?) problem JFDC FLUENT 1 July 11, 2011 05:59
natural convection problem for a CHT problem Se-Hee CFX 2 June 10, 2007 06:29
Adiabatic and Rotating wall (Convection problem) ParodDav CFX 5 April 29, 2007 19:13
Is this problem well posed? Thomas P. Abraham Main CFD Forum 5 September 8, 1999 14:52


All times are GMT -4. The time now is 10:07.