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MAB May 19, 2008 11:34

Mesh @ Free Surface
 
hi I am trying to creat regular waves in one domain. Do you have any idea how to handle the mesh at free surface. or how to achieve a finer mesh at free surface withing the range of wave amplitude.

thanking in advance

MAB

Mehul May 23, 2008 00:27

Re: Mesh @ Free Surface
 
Hi MAB,

It don't know much about your system, But if you want to create free surface between water and air in one geometry. Then two seperate domains should be created and the region where the seperation occurs, you will require fine mesh. Divide whole verticle height in three domains, mesh individually, then using CEL expression define different material for different domains. Assume this could help you..


MAB May 23, 2008 10:48

Re: Mesh @ Free Surface
 
Hi Mehul thanks allot for your advice, I like this idea of 3 domains. Could you please explain me bit more about "how to define the multiple domains" . Also if you could tell more about how to create mesh using CEL. is there any tutorial on this.

bundle of thanks. MAB

Jonathan May 26, 2008 13:12

Re: Mesh @ Free Surface
 
It is problematic to achieve a detailed enough mesh using unstructured tetra elements without getting way too many elements.

This is because you need very fine mesh in the isosurface W direction, but you don't need fine mesh along the UV-directions. Unstruct tetras will give you fine mesh in three dimensions and your element count goes very high.

In this case a structured mesh works much better, since you can have very flat elements.

As an example I use a mesh with 10 mm W resolution but around 0.1-0.3 m UV resolution for yacht hull free surface simulations.

Phil May 27, 2008 08:09

Re: Mesh @ Free Surface
 
You can also use an unstructured mesh by using stretched prism elements (inflation) off the quiescent free surface location.

MAB May 27, 2008 10:28

Re: Mesh @ Free Surface
 
I have used a line spacing control to achieve a fine mesh at free surface. it works fine in 2D. But how can a implement it in 3D. Any Idea????????????

Phil May 28, 2008 13:25

Re: Mesh @ Free Surface
 
If you create the 'water' and 'air' portions as separate 3D regions when you create the geometry, you should be able to inflate off of the region boundaries. This is possible with CFX Mesh, not sure about other meshers. The separate 3D regions can be included in the same domain when you define the physics.

MAB May 29, 2008 04:48

Re: Mesh @ Free Surface
 
Hi Phill, Thanks for this idea. it seems perfect. Could you give me any further tips on how to define separate 3D regions.is there any tutorial on this? Should I just draw two separate rectangles with a common face (interface of water and air) and then extrude it to make 3D?


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