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# Defining Mesh

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• ### Defining Mesh

Posted by Kwun Ho Ngan at May 28. 2007
I am trying to apply the various hypothesis for the mesh.

How does the automatic length being defined? What does this 'fineness' refer to? and what does the 'Max. Element Volume' refer to for 3-d meshing? Does it mean the number of cells enclosed in the body or..?

Also, is there a 'maximum' mesh size that I can create using Salome?

I am a fairly new user of CFD softwares so there might be some fundamental problems that I might not be aware of.

Many Thanks
• ### Re: Defining Mesh

Posted by Grigory Zhivotovsky at May 29. 2007

Hi Kwun,

You can find related information in HELP.

In particular 'fineness' is the quality of the future mesh, ranging from 0 (coarse mesh, low number of elements) to 1 (extremely fine mesh, great number of elements).

'Max. Element Volume' sets the maximum volume of each cell and defines quantity of tetrahedrons or hexahedrons created inside your shape during 3D meshing (1D hypothesis define meshing of edges and 2D  hypothesis define meshing of boundary faces).
'Maximum' mesh size can be defined directly by
Netgen 2D and 3D hypotheses.

Regards,

Grigory
• ### Re: Defining Mesh

Posted by Kwun Ho Ngan at May 29. 2007

What I was unclear of is if I can actually know the exact size of each cell. Reason being that I would like to find out how 'fine' I need to optimise the mesh to identify an interface in a two phase flow.

With regards to the numbers, say 0 to 1, is there any unit attached to it or any maths behind what is 0 and what is 1? I am abit unsure what a difference (and how much a difference) between a 0.8 or 0.9 if i choose the fineness and the max. volume of element.

Any help on such topic?

Many thanks.
• ### Re: Defining Mesh

Posted by Kwun Ho Ngan at May 29. 2007

What I was unclear of is if I can actually know the exact size of each cell. Reason being that I would like to find out how 'fine' I need to optimise the mesh to identify an interface in a two phase flow.

With regards to the numbers, say 0 to 1, is there any unit attached to it or any maths behind what is 0 and what is 1? I am abit unsure what a difference (and how much a difference) between a 0.8 or 0.9 if i choose the fineness and the max. volume of element.

Any help on such topic?

Many thanks.
• ### Re: Defining Mesh

Posted by Grigory Zhivotovsky at May 29. 2007

Hi,

You can use any value between 0 and 1. You have to build a few meshes to compare them and find a value you need. If you want to have exact size use another hypothesis.

Regards,

Grigory

• ### Re: Defining Mesh

Posted by Kwun Ho Ngan at May 29. 2007
Thanks for the assistance.