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-   OpenFOAM Mesh Utilities (http://www.cfd-online.com/Forums/openfoam-meshing-utilities/)
-   -   Surface boundary mesh in snappyHexMesh (http://www.cfd-online.com/Forums/openfoam-meshing-utilities/61511-surface-boundary-mesh-snappyhexmesh.html)

bastil November 20, 2008 15:39

What are you exactly unhappy w
 
What are you exactly unhappy with? For me this does not look so bad. However prism layers at the front run off without any obvious reason. Gap is not resolved between two wings.

lhcamilo November 21, 2008 11:50

Well, while I agree that it is
 
Well, while I agree that it is not so bad, I do believe that there is room for improvement, specially with respect to the surface boundary layers. Thus I was wondering if there was any thing anyone could suggest as a means to fine tune or optimize the mesh (which would be very welcome and greatly appreciated).

Is there any parameter that could be improved or any thing that I have overlooked?

I am rather new with OF so thanks in advance for bearing with me.

regards

lhcamilo November 25, 2008 04:43

Just a means of comparison, he
 
Just a means of comparison, here's a mesh done with Harpoon

Harpoon Mesh

I was wondering if a similar result with results with snappyHexMesh with respect to the boundary layer Mesh. Also any tips about how to resolve the gap between the two wings would be very much appreciated.

Thanks in advance

fra76 November 25, 2008 08:39

You can refine the surface to
 
You can refine the surface to a constant level, so that the prism layer will have a constant height.
For example:

refinementSurfaces
{
spoiler
{
// Surface-wise min and max refinement level
level (8 8);
}
}

Hope this helps,
Francesco

lhcamilo November 25, 2008 12:48

Thank you for the tip francesc
 
Thank you for the tip francesco, it did help. Now the surface level looka great deal bette.

Also I managed to separate the two airfoils by introducing another refinement box at that point. Here's a pic:spoiler new

Besides the noticeable progress the boundary layer still won't form at the LE, I don't really understand why it won't.

unfortunalely my OF breaks when I run it with surface levels of (8 8). It say it runs out of virtual memory, the final mesh has about 1.2E6 cells I am not really sure why the memory runs out. I am going to do some research on the forums to get that sorted out, again any tips are more than welcome(decomPar also breaks).

Thanks a lot for the help, I really appreciate it

regards

Leo Camilo

lhcamilo November 26, 2008 05:24

UPDATE I've been trying to
 
UPDATE

I've been trying to run the case now with boundary layers included (3) with refinenment levels up to (8 8). If I run the case without the layers I get the result from the post above. However the moment I add layers snappyHexMesh runs for a while but then I get the following message

new cannot satisfy memory request.
This does not necessarily mean you have run out of virtual memory.
It could be due to a stack violation caused by e.g. bad use of pointers or an out of date shared library
Aborted


The case has about 1.2E6 cells and I am running it on a 32 bit quad-core box with 4GB of RAM with Fedora 9, I am not sure why this is happening.

any ideas

thanks in advance

leo

lhcamilo December 10, 2008 07:13

Hello there fellow foamers, I
 
Hello there fellow foamers, I have a few updates on the case spoiler I have been running. From my last screenshot snappyHexMesh(sHM) was able to distinguish between the two airfoils, but there was still an issue with the boundary layers.

well here's an update on my latest attempt
Overview
upper TE
lowerTE
lowerLE
upperLE


As it can be seen from the overview I have tried introducing refinement boxes around the TE trouble areas and have added a larger refinement area around the whole structure. The large and smaller boxes have a max refinement level inside of 7 and 8 respectively.

Despite all that, unfortunately some of the problems still persist:
  • The boundary layer seems to disappear around the LE, creating hole, for no apparent reason
  • Despite the refinement boxes the boundary layers still have trouble attaching at the TE of the structure

I do realize that attachment at the lower TE is challenging, but is it doable with sHM? Is there a way of solving the other problems? I don't increasing the ref level is going to be a great idea, I am already dealing with 9E6 cells, thankfully I am able to use a more powerful box. but anyway, are there any pointers? I am posting my sHMDict below:

sHMDict

Have I misused any features or parameters?

Anyway thanks for any help you can give me,

regards

claco February 3, 2012 08:37

Quote:

Originally Posted by lhcamilo (Post 184577)
Hello there fellow foamers, I have a few updates on the case spoiler I have been running. From my last screenshot snappyHexMesh(sHM) was able to distinguish between the two airfoils, but there was still an issue with the boundary layers.

well here's an update on my latest attempt
Overview
upper TE
lowerTE
lowerLE
upperLE


As it can be seen from the overview I have tried introducing refinement boxes around the TE trouble areas and have added a larger refinement area around the whole structure. The large and smaller boxes have a max refinement level inside of 7 and 8 respectively.

Despite all that, unfortunately some of the problems still persist:
  • The boundary layer seems to disappear around the LE, creating hole, for no apparent reason
  • Despite the refinement boxes the boundary layers still have trouble attaching at the TE of the structure

I do realize that attachment at the lower TE is challenging, but is it doable with sHM? Is there a way of solving the other problems? I don't increasing the ref level is going to be a great idea, I am already dealing with 9E6 cells, thankfully I am able to use a more powerful box. but anyway, are there any pointers? I am posting my sHMDict below:

sHMDict

Have I misused any features or parameters?

Anyway thanks for any help you can give me,

regards

Hi,

Have You solved Your troubles with boundary layer? I have the same problems. It seems like that SHM creates the layers in some regions, whereas it does not create them in other regions (like in the Upper TE region).

Claudio.


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