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-   -   Moving/diforming mesh (http://www.cfd-online.com/Forums/fluent/27825-moving-diforming-mesh.html)

Ali August 9, 2000 15:59

Moving/diforming mesh
 
Hi

I am trying to simulate a petrol engine using Fluent software.I have started with a simple cylinder & piston. I have faced a few problems, especially with moving boundries & moving meshes. I would appreciate if can get some help regarding this matter.

Ali

Ahmed Hassaneen August 11, 2000 02:49

Re: Moving/diforming mesh
 
Hi Ali, I don't think Fluent has the capability of moving grid by changing the geometrical boundary condition which is the case in Piston engine. However, I believe you can do so by changing the flow boundary with time as the piston moves from BDC to TDC. Goodluck. =Ahmed=

Maurizio August 11, 2000 06:02

Re: Moving/diforming mesh
 
Dear Ali,

to better understand your question, can you tell me which approach are you using in Fluent? Did you already set up a moving boundary representing the piston or you have imposed some sort of boundary condition to simulate this motion?

Looking for your answer.

Cheers

Maurizio

Kai Kang August 11, 2000 09:29

Re: Moving/diforming mesh
 
Fluent can model the sliding motion of the piston, but not has the deforming mesh capability, so I would be interested to know, too, how to set up the boundary condition in this case...

Ali August 13, 2000 10:08

Re: Moving/diforming mesh
 
Thanks everybody who contributed towards solving my problem. I think, I could managed to sort out the problem by considering the piston as dead region (shown below). While the piston is in different position, I created geo & grid files, keeping the same number of nodes (for the geometry) and I & J for dead cells. The results for 2-D steady state and without valves seem OK. Regarding the movement of the valves I can do the same but since the valves touch the intake wall when they are closed, some meshes are disappeared and there will be two mesh regions upatream and downstream of the valves. I am studying this problem and I will appreciate if some one can help me.

With regards,

Ali

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oliver August 24, 2000 13:51

Re: Moving/diforming mesh
 
Hi Ali

There is a tutorial in fluent user manuals, Fluent 4.5/4.4 (structured), I think. Which shows how to use fluents deforming mesh module.

Read this, this alone should be a good starting point

Regards

Oliver

Ali August 26, 2000 01:39

Re: Moving/diforming mesh
 
Dear Oliver; Thank you very much for you comment. It is good for moving objects like a piston. But for the valves which touch the wall and the mesh in between valve and the cylinder (or intake) wall will be destroyed (as the valve get close to the wall) there is noting mentioned. In this position the meshing topology will be different. This is the point I am trying to sort it out !!!???

Ali

oliver August 28, 2000 16:03

Re: Moving/diforming mesh
 
Hi Ali

If the valve touches the wall, the cells around this location will have to become dead or wall cells, therefore the identical domain topology will be destroyed so it will not work. However you can simulate the value prior to the point of complete closure.

Regards

oliver

Ali August 29, 2000 10:39

Re: Moving/diforming mesh
 
Dear oliver, Thanks again. I am working on it. I will let you know if I could get any positive result.

Ali

Sung-Eun Kim August 31, 2000 20:05

Re: Moving/diforming mesh
 
FLUENT 4.5 has a limted capability to handle deforming mesh. There are users who have come up with workarounds and tricks to deal with non-trivial deforming mesh applications. Yet there will still be a limit to what 4.5 can offer.

FLUENT 6.0 will have a far more comprehensive, easy-to-use moving/deforming mesh capability.


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