|
[Sponsors] |
[snappyHexMesh] 2D Cylinder mesh problems with Snappy |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
September 13, 2010, 05:40 |
2D Cylinder mesh problems with Snappy
|
#1 |
Senior Member
|
Hi Foamers,
I'm trying to mesh a 2D cylinder (1 cell in z direction) using snappy, following the tutorial tutorials/incompressible/pimpleDyMFoam/wingFlutter, where a 2D airfoil is meshed with snappy. It seems that with my settings snappy is not capable to recognize correctly the cylinder (that is an stl surface obtained with gmsh), and it doesn't cut the mesh. I attach the resulting mesh, blockMeshDict and snappyHexMeshDict. Could anybody help me to fix it? Thanks, Ivan http://img547.imageshack.us/i/snappycyl.jpg/ http://img821.imageshack.us/i/snappycylonly.jpg/ http://img547.imageshack.us/i/snappycylzoom.jpg/ Last edited by wyldckat; September 3, 2015 at 17:47. Reason: disabled embedded images |
|
September 13, 2010, 11:22 |
|
#2 |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
Hi Ivan,
It looks like there is a problem with your stl file. The surface cylinder is not closed. Also your refinement boxes seem messed up. If you're doing 2D they should be like this: refinementBox1 { type searchableBox; min (-1 -0.5 -0.1); max ( 1 0.5 0.1); //changed 0.06 to 0.1 } refinementBox2 { type searchableBox; min (-0.05 -0.05 -0.1); max ( 0.05 0.05 0.01); //changed -0.01 to 0.1 } otherwise with the old settings you will probably get more than one cell in the z-direction. |
|
October 26, 2010, 21:02 |
|
#3 |
Senior Member
Daniel
Join Date: Jul 2009
Location: Montreal, Canada
Posts: 156
Rep Power: 17 |
Hi Ziad,
I am running into a problem that you might have an answer to, given your last response to Ivan. I am trying to make snappyHexMesh produce a 2D mesh on the airfoil in the wingMotion tutorial. I tried changing the snappyHexMeshDict refinement box as follows: Code:
refinementBox { type searchableBox; min (-1 -1 -0.1);//min (-1 -1 -1); max (5 1 0.1);//max ( 5 1 1); } I posted this issue first a couple of days ago in another thread (http://www.cfd-online.com/Forums/ope...-tutorial.html) before I saw your post. Thanks, Dan |
|
October 26, 2010, 21:22 |
|
#4 |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
Hi Daniel,
I tried once to make a 2D mesh with sHM but got more than one cell in the z direction. I think this is due to the fact that sHM divides whatever you have initially in blockMesh in the z direction by the specified number of levels. Not sure how to get around that. Since it was a simple rectangular shape I ended up using blockMesh which is quite good for simple cartesian shapes. Try maybe meshing only one of the empty bc planes with sHM and then extrude the mesh in the z direction? You should only have one z coordinate throughout sHMDict. Let me know how it works. Ziad |
|
October 26, 2010, 21:36 |
|
#5 |
Senior Member
Daniel
Join Date: Jul 2009
Location: Montreal, Canada
Posts: 156
Rep Power: 17 |
Hi Ziad,
Thanks for the response. The z-coordinate only appears twice in sHMdict, where the boundingbox is defined. Unfortunately, I do not think the extrude function will not work for me because I have divided my geometry (airfoil) into two patches (a wing and a flap), but since there is one continuous object, extrude followed by autoPatch would recognize the airfoil as only one patch. Is it possible to delete the offensive points, blocks and edges from the polyMesh directory manuallly? I imagine this might be next to impossible. I'll keep working this. Thanks again, Dan |
|
October 26, 2010, 22:10 |
|
#6 | |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
Quote:
|
||
October 27, 2010, 03:25 |
|
#7 | |
Senior Member
|
Hi Daniel,
I've answered you about 2D in SHM on your other thread. Can you give me in more details your problem in extruding an unconnected boundary like a wing with a slat? I have a very similar problem, for which I'm managing to use extrude... Quote:
|
||
October 27, 2010, 08:50 |
|
#8 | |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
Quote:
|
||
October 27, 2010, 17:01 |
|
#9 |
Senior Member
Daniel
Join Date: Jul 2009
Location: Montreal, Canada
Posts: 156
Rep Power: 17 |
Hi Ziad,
I tried setting the boundingBox coordinates in the same xy plane, however this just eliminated the effect of the boundingBox. I am very interested in using the extrusion to cut the mesh. Can you please provide some detail about how to do this? Looking at the extrudeProperties dictionary, I do not see how it is possible to cut the mesh. I have attached pictures of the side view of the mesh. The zoomed-out pic shows the majority of the domain as 1-cell deep, with a white square in the center. The zoomed-in pic shows the upper-left corner of this white square, which is in fact a highly resolved mesh of the front/back of the airfoil. If I extrude the empty front patch one cell, will it cut one "airfoil thickness" cell, or one "majority of the domain" cell deep? Thanks, Dan |
|
October 27, 2010, 18:43 |
|
#10 | |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
Hi Dan,
The extrude/cut process involves using extrudeMesh (which doesn't cut) first and then splitMesh (which cuts) to make the internal boundary external. splitMesh is a bit tricky to use. Will take a look at both later tonight and post what I can come up with. Just a thought about using sHM in pure 2D mode, you'll probably have to start up your domain in blockMesh with blocks consisting of one flat plane. You'd have to collapse one empty plane into the other, or in other words, use exactly the same physical points on both empty planes. Ziad Quote:
|
||
October 27, 2010, 20:38 |
|
#11 |
Senior Member
Daniel
Join Date: Jul 2009
Location: Montreal, Canada
Posts: 156
Rep Power: 17 |
Hi Ziad,
There is also another tool called "removeFaces" which, from the brief description in the user guide, should merge cells. If I could do this to all of the cells across the z-axis, then I would arrive at a 2-D mesh. Have you used removeFaces before? I have looked at the code and scanned the boards, but documentation on using it appears to be scarce. Code:
Usage: removeFaces <faceSet> [-overwrite] [-parallel] [-case dir] [-help] [-doc] [-srcDoc] Dan Thanks, Dan Last edited by dancfd; October 27, 2010 at 21:24. |
|
October 28, 2010, 21:31 |
SnappyHexMesh in 2D
|
#12 |
Senior Member
Daniel
Join Date: Jul 2009
Location: Montreal, Canada
Posts: 156
Rep Power: 17 |
In case anyone is interested, I have attached a script that can be run in Octave that will read the points and faces files of a mesh and output all of the internal faces parallel to the empty patches into a faceSet file. Place the faceSet file in the polymesh/sets directory, run removeFaces remFaces -overwrite, and you will transform your snappyHexMesh from 3D into a 2D mesh. I just tried it on the movingWing tutorial and it appears to have worked. Note that the z-coordinates of the empty patches must be entered in the script - it is hardcoded for z = +- 0.1 now. Enjoy.
Dan |
|
October 30, 2010, 14:05 |
creating a 2D mesh with snappyHexMesh
|
#13 |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
Hi Daniel,
I finally got to spend some time on this and figured out how to do it using only OpenFoam tools. The procedure outline is the following but does not require splitMesh:
|
|
October 30, 2010, 18:05 |
|
#14 |
Senior Member
Daniel
Join Date: Jul 2009
Location: Montreal, Canada
Posts: 156
Rep Power: 17 |
Hi Ziad,
I cannot thank you enough. What you have done is far easier than the method I had attempted. I really appreciate you taking the time to explain everything in such detail as well. Regards, Dan |
|
October 30, 2010, 18:15 |
|
#15 |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
You're quite welcome Daniel. I've been promising myself to formalize this for a while now so thanks for providing a little nudge. This is all going towards creating a wiki page.
what are you working on by the way? |
|
October 30, 2010, 21:20 |
|
#16 |
Senior Member
Daniel
Join Date: Jul 2009
Location: Montreal, Canada
Posts: 156
Rep Power: 17 |
I am trying to create a simulation of a wing with an oscillating flap. I began with a basic c-grid using blockMesh, but I could not get the diffusivity to work and the mesh turned itself inside out at the trailing edge. The diffusivity works fine on the movingWing example, but I could not create the same mesh in 2D until now. Apart from creating the wiki, what are you working on?
Dan |
|
October 31, 2010, 09:57 |
|
#17 |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
Interesting problem. Are the oscillations self-induced or operator driven?
My work is on snow, ice and rain simulations using two-fluid formulations. I've done some work in aircraft icing as well. |
|
November 1, 2010, 16:32 |
|
#18 |
Senior Member
Daniel
Join Date: Jul 2009
Location: Montreal, Canada
Posts: 156
Rep Power: 17 |
The oscillations are operator-driven. Aircraft icing and multi-phase simulations sound very interesting as well!
|
|
April 26, 2011, 06:00 |
|
#19 | |
New Member
RDG
Join Date: Feb 2011
Posts: 29
Rep Power: 15 |
Quote:
Any idea how to manage this? |
||
April 27, 2011, 11:47 |
|
#20 |
Senior Member
Join Date: Mar 2009
Location: My oyster
Posts: 124
Rep Power: 17 |
It sounds like your dict file is not properly set up. Can you post your case as a tar.gz attachment?
|
|
Tags |
2d mesh, airfoil, cylinder, extrudemesh, snappyhexmesh |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
[snappyHexMesh] Help with Snappy: no layers growing | GianF | OpenFOAM Meshing & Mesh Conversion | 2 | September 23, 2020 08:26 |
[snappyHexMesh] Snappy Hex Mesh - issue with smoothness of the model edges | olek.warc | OpenFOAM Meshing & Mesh Conversion | 1 | August 31, 2018 11:31 |
[snappyHexMesh] Snappy Hex Mesh Generation: error preventing the .eMesh file generation. | Mariana Garcia | OpenFOAM Meshing & Mesh Conversion | 1 | January 7, 2016 04:24 |
[snappyHexMesh] Layers:problem with curvature | giulio.topazio | OpenFOAM Meshing & Mesh Conversion | 10 | August 22, 2012 09:03 |
Ugly mesh around cylinder | rks171 | STAR-CCM+ | 4 | May 9, 2012 14:35 |