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-   -   Highly skewed elements (http://www.cfd-online.com/Forums/fluent/45481-highly-skewed-elements.html)

AK July 23, 2007 17:18

Highly skewed elements
 
Hi.

Firstly let me thank all who have responded to my previous post regarding the mixing of two fluids.Thank you.

My question this time is about meshing of a 3D model which consists of an intersection of two cylinders and a cylinder and a brick ( All united to form one model). I am facing the problem of highly skewed cells.

If you are interested in having a look at the model then please email me.

Thank you.

AK

AK July 23, 2007 17:25

Re: Highly skewed elements
 
Here is the link.

http://picasaweb.google.com/athakhan/Model

Joe July 23, 2007 18:41

Re: Highly skewed elements
 
Post pics of your initial meshing efforts.

AAA July 23, 2007 19:47

Re: Highly skewed elements
 
Hey

If you can export you highly skewed mesh it to Fluent, use the smooth/swap option as well as the adapt->iso-value->grid->cell Equiangle sqewness to solve the problem.

Alternatively, Start by meshing the red, green and blue volumes first. then mesh the faces of the large cylinder only. Then use a "size function" with a growth factor of no more that 1.2 to mesh the core. Start the meshing from the faces between it and the adjacent small volumes as well as the faces of the cylinder. use tetrahedral mesh.

Good luck! AAA

AK July 23, 2007 20:45

Re: Highly skewed elements
 
AAA:

The volume is one entity. So how can I mesh each element separately. Moreover, is it not possible to get a hexahedral mesh?

AAA July 24, 2007 06:40

Re: Highly skewed elements
 
Hey AK,

If you have merged all the volumes into one entity (one volume as your domain), you've made a mistake. This way, You won't have control on the mesh.

Start by having separate volumes (reds, blues, etc.) and then try performing what I've explained earlier.

REMEMBER! Any internal face between any two adjacent volumes in the domain (i.e., between a red vane and the grey cylinder) is considered as an interior, not as a wall. So you don't have to have "one entity" to have the flow running through your domain. (Divide and rule!)

Regards AAA

mak July 24, 2007 08:33

Re: Highly skewed elements
 
Hi,

the model looks like having some edges/faces running tangential into the cylinder. As Gambit creates nodes on every edge, there are likely some elements highly skewed in the model at these connections. Try to remove these, either by creating virtual geometry or by changing the geometry.

regards,

mak

AK July 29, 2007 17:01

Re: Highly skewed elements
 
Hi Friends,

Thank you for your responses.

I meshed the model by dividing it into smaller geometries. It still did not solve the problem of skewness. I read the grid into fluent and used adapt - smooth mesh to improve the condition. Now, when I iterated the solution for sometime and checked the plots (contour) the only thing I could see were the rectangular inlets. The rest of the geometries do not display. What could be the reason?

The rectangular inlets have velocity inlet BC imposed on them.

Thank you.

AK


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