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Viscous Layers problem

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Viscous Layers problem

Posted by Kristin Newlands at September 29. 2011

Hello,

I'm having problems with applying the Viscous Layers hypothesis to my annular geometry and I would really appreciate some help.

Originally, I created the annular cylinder with R1=12.5, R2=25 and L=75, as I was under the (wrong) impression that Salome's units were mm. This caused me confusion when I set-up my case in Code_Saturne (which, as far as I understand, uses metres), so I re-created my geometry with R1=0.0125, R2=0.025 and L=0.075. However, when I proceed to mesh it, exactly as I had done for the previous model (see attached Screenshot), it succeeds in computing a mesh when I don't apply the Viscous Layers, but crashes when I enable it.

Is the problem due to the size of my model? I really need to practice a basic case before I increase the complexity, so I wanted to keep the domain small for faster simulations.

Thank you,

Kristin

 

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Re: Viscous Layers problem

Posted by Saint Michael at October 03. 2011

Hi Kristin

Maybe the reason of the crash is a too high Thickness of the Viscous Layers?

St. Michael

Re: Viscous Layers problem

Posted by Kristin Newlands at October 03. 2011

St. Michael,

 

Thank you very much for your reply. I did question whether the thickness of the viscous layers was too high, but even though I reduce it, I am not successful in obtaining a mesh. I don't understand where the problem is, since all I changed are the dimensions of the geometry and I don't know what else to do to avoid the crash.

 

I desperately need this mesh to work and I attach a python dump of my geometry and mesh setup. Any advice that would help me make some progress would be greatly appreciated.

 

Best regards,

 

Kristin

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Re: Viscous Layers problem

Posted by Saint Michael at October 03. 2011

If I change
Viscous_Layers_1.SetTotalThickness( 4 ) -> Viscous_Layers_1.SetTotalThickness( 0.001 )
in your script, the mesh is computed OK after replaying your script.

St. Michael

Re: Viscous Layers problem

Posted by Kristin Newlands at October 03. 2011

Of course, that makes perfect sense. I was making a very silly mistake.

Thank you for taking the time to help me,

Kristin

Re: Viscous Layers problem

Posted by Jeroen van der Vossen at December 01. 2011

Dear Salome users,

I am actually new to the forum since I recently started using Open Foam, with Salome to make the meshing. A colleague of mine gave me a tutorial for using Salome in combination with Open Foam. This makes a Submarine, which should be calculated. Now at a certain point I have to give the mesh itÅ› viscous layers, but then it tells there is a "segmentation violation in address 0". I have tried practically everything I could think of with my little knowledge of Salome. I am using the the latest version 6.3.1. Is there someone who knows how to solve this problem?

On the Internet I was reading about segmentation violation, and there they say that for some reason my CPU can access a certain memory, or something. I have no idea of what is going on with it.

Please help, I can continue my learning process because of this error.

 The viscous layer is set up as thickness 10, number of layers 8, stretch factor of 1.2.

Further I am using Netgen 1D-2D for meshing in 2D, and afterwards I am meshing with Tetrahedron (Netgen) in 3D. on the fourth step I am adding the viscous layers and then it gives an error. With the 2D meshing I am giving Hypothesis in Netgen 2D simple parameters, with number of segments set to 8 for the farfield, and local length of 25 for the body of the submarine, and local length of 5 for the small rounded edges.

I am unable to upload the model because it is about 10 MB.

Thanks a lot,

Jeroen

Re: Viscous Layers problem

Posted by Duncan Roy van der Heul at December 01. 2011
There is a bug in the version 6.3.1

viscous layer algorithm

Read this:

http://www.salome-platform.org/forum/forum_10/372035859

 

You have to download the patch and rebuild the SMESH module.

 

Cheers,

Duncan

Re: Viscous Layers problem

Posted by DAVID Gilles at December 01. 2011

Hello,

Or you can wait a little for the next version (6.4.0) to come, in which the bug is fixed.

It should be a matter of days :)

Gilles

Re: Viscous Layers problem

Posted by Jeroen van der Vossen at December 01. 2011

Ohw thanks. In Salome 6.3.0 it isn't useable is it? Well I am not really sure how to rebuild the SMESH module. I actually don't have a lot of knowledge of programming, or Ubuntu. So I think I will have to wait a few days then.

Thanks for the quick replies.

Re: Viscous Layers problem

Posted by Jeroen van der Vossen at December 14. 2011

Well after a little waiting, I am wondering if there is somebody who can tell me how to rebuild that SMESH module? Is there an easy way to do this, a sort of step by step explanation or something?

Re: Viscous Layers problem

Posted by sebastian nowak at July 25. 2013

Hello Salome User,

i want to create a mesh with hexahedron (i,j,k) algorithm and insert visous layers (salome 6.6.0); my geometry is a pipe surrounded by a box (pipe cut of the box). But when i try to mesh my case, i am getting a mistake;  

My idea is to rise the number of segments in the shortness of the pipe; How would you create a mesh with visous layers close to the pipe? which algorithm and which settings to use?

Thank you!

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Re: Viscous Layers problem

Posted by William Tougeron at July 26. 2013

Hello Sebastian,

If you want to use the Hexahedron (i,j,k) algo, so you have to create a blocking in the Geometry module.

Enclosed is a dump of a Salome study showing an example of how to do it (but there are many other possibilities). You can adapt it to your case modifying the parameters inside the script.

Best regards

William

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Re: Viscous Layers problem

Posted by sebastian nowak at July 26. 2013

Thank you, William Tougeron :)

Now i am asking myself how to get information about the mesh structure; the smallest element size; the largest element size; i am playing with viscous layer to create a fine mesh close to the pipe, but how?
what to change at Total thickness; Number of layers; Stretch factor; i changed the factors but nothing seems to change visible? :)

Any good advices? :)

Thank you

Re: Viscous Layers problem

Posted by sebastian nowak at July 26. 2013

In Ansys i can select a surface and i can define the number of inflation layers and inflation growth rate, but in Salome under viscous Layers i am unable to do this in a similar way; Can anyone help me, please ;)

 

Best Regards

Re: Viscous Layers problem

Posted by sebastian nowak at July 28. 2013

Hello,

in my case study i want to create a fine mesh close to the pipe (A Cylinder cut off a Box); can anybody help me to improve my mesh; i want a viscous layer around the pipe, but i am unable to create it :)

Best Regards

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Activate by Kristin Newlands on Sep 29, 2011 06:23 PM
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