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# Emergency! Using hexahedral and tetrahedron meshes

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### Emergency! Using hexahedral and tetrahedron meshes

Posted by mohammad fereshtehpour at September 02. 2012

Dear Friends

Hi

I have a problem in meshing the following geometry. As you can see in the picture I want to use both hexahedral and tetrahedron  meshes together. I need to have a viscous layer ationat the bottom. But during computation it faces a problem as follows:

invalid input mesh. Can't build pentahedral mesh on viscous layers

What can I do? Please help since my thesis is directly related to overcoming this problem.

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### Re: Emergency! Using hexahedral and tetrahedron meshes

Posted by mohammad fereshtehpour at September 02. 2012

I used the following hyp.s:

Main Mesh:

Auto Tetra. with 1D automatic length=0

Submesh:

Auto Hexa with 1D Automatic length=0, Also I used viscous layer: thickness=0.03, no.=10, factor=1.25

Thanks in advance

### Re: Emergency! Using hexahedral and tetrahedron meshes

Posted by Saint Michael at September 03. 2012

Hi

Could you provide a study or a script to see what is wrong?

St.Michael

### Re: Emergency! Using hexahedral and tetrahedron meshes

Posted by Martin Herling at September 05. 2012

Hi all,

I´m wondering about the same error for a long time,

'Invalid input mesh. Can't build pentahedral mesh on viscous layers'

till I decided to build the wall layers myself. But I´m still interested if there´s a solution to this, also because my self-built wall layers aren´t orthogonal to the walls in all cases....

Attached is the script for the half of a cut through a nozzle. Sometimes it seems that the mesh is computed successful, but still the error appears. I experienced that playing with the 'viscous layer' parameters sometimes helps, but since I want to parametrize the geometries and build the meshes automatically, this is not really an option.

regards,

Martin

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### Re: Emergency! Using hexahedral and tetrahedron meshes

Posted by SMESH expert at September 06. 2012

Hello Martin

Thank you for your post. Your case reveals a bug in Hexahedron (i,j,k) algorithm. A fix will be available in the next SALOME version.

Sorry for inconvenience.

Best regards

Edward

### Re: Emergency! Using hexahedral and tetrahedron meshes

Posted by SMESH expert at September 06. 2012

Dear Martin

The attached script provides a workaround for this bug.

Best regards

Edward

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