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JAlbert July 25, 2013 04:30

mesh motion help request
Hello everybody;

I am going to model pitching naca 0012 in CFX. I am a new user. I have two questions.

1- In order to simulate pitsh motion which means have mesh motion, Is it true to rotate all the domain with specified angular velocity or do I have to make one region near airfoil and one outer and just rotate the inner region ( one in near airfoil)? Does it make any difference in results ? If there is no difference, I think rotating the entire domain would be easier, of course velocity direction of inlet is still fixed in ,for example ,X-direction.

2-In Fluent there is an option which you can see contours of any variable or mesh motion every time step in calculation activities, solution animation part. Is there such a capability in CFX?How to do that?

Thanks in advance.

ghorrocks July 25, 2013 08:05

This would be best done by putting the airfoil in a rotating frame of reference and linking it with the rest of the stationary geometry by a GGI. THen you can isolate the rotating bit to just around the airfoil and your outer boundaries do not need to move.

JAlbert July 26, 2013 02:27

Thank you Glenn for your reply;

As you know, in order to use reference frame I must activate "Rotating" in that region near airfoil. Now I want to know :

1- Should I activate mesh deformation option for any of rotating or stationary subdomains or not? I have meshed the inner region with boundary layer quality and I do not want my initial mesh quality change during solution.

2- What about plunge simulation? Should I divide the domain into two subdomains again or , no, oscilating the entire domain vertically will yield in physical results?

Thanks a lot for your kind.

ghorrocks July 27, 2013 07:02

Only use rotating frames of reference if he only motion is rotary. If other motions are present I would not use it but then use a general moving mesh.

What is a plunge simulation?

JAlbert July 27, 2013 09:20

By plunge simulation, I mean translating the airfoil vertically by a Sine function ,for example. Now do I have to separate the domain into two subdomains or no one entire domain is enough? How does CFX start to remesh? In fluent you can choose whether just smooth the domain or both smooth and remesh. How does remeshing option activates in CFX?

Thanks a lot.

ghorrocks July 28, 2013 07:33

If the foil is translating (not rotating) then you need to use moving mesh, at least for that application. I would do it as one moving mesh domain. But make sure the outer boundaries do not move (unless they are meant to move).

Yes, CFX supports remeshing.

JAlbert July 29, 2013 08:31

Thanks for your reply;

Is it possible to monitor mesh displacement or mesh motion in CFX during CFX solution like Fluent mesh animation option?

ghorrocks July 29, 2013 21:40

Yes. Define a monitor point with a CEL expression to look at Mesh X/Y/Z Displacement.

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