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Translating mesh interface in cfx11.0 ?

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Old   September 5, 2008, 09:27
Default Translating mesh interface in cfx11.0 ?
  #1
Sam
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Hi folks:

I am trying to solve a 2d transient rotor-stator problem using cfx 11.0. My geometry consists of 1 vane passage matched to 4 rotor passages. There is a time dependent gust specified at the vane inlet " i.e. the unsteadiness is not just due to rotor motion.

The simple way to set this up is to specify a constant y velocity to the rotor mesh and have a sliding mesh interface between the vane and the rotor meshes. In brief, this is a 2d cascade simulation, but with a moving rotor mesh. I have already done this simulation using another cfd code and it works fine.

In cfx, there are 2 problems: 1)grids have to be 3d. This can be handled by extruding a 2d mesh into 3 planes. 2)Under transient rotor-stator in the cfx manual it says:

"Translational relative motion is not supported at a transient sliding interface (only rotational motion is supported)."

Does that mean that this problem is essentially not doable in cfx11.0 ? Or is there another way?

Thanks for your help.

Sam

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Old   September 7, 2008, 19:44
Default Re: Translating mesh interface in cfx11.0 ?
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Glenn Horrocks
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Hi,

I don't understand what you are trying to do. I have used translational GGIs and they work fine for me.

Glenn Horrocks
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Old   September 8, 2008, 15:44
Default Re: Translating mesh interface in cfx11.0 ?
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Sam
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Hi Glen,

I am trying to simulate rotor-stator interaction in a 2d study.

Could you please elaborate how you have used translational GGI's ?

I have already quoted what the manual says. The only additional thing that tech support suggested was to use a large radius and substitute an equivalent rotation for translation.

sam
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Old   September 8, 2008, 18:59
Default Re: Translating mesh interface in cfx11.0 ?
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Glenn Horrocks
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Hi,

Can you describe what you are trying to do? Are you trying to model one of those cylindrical fans? That is the only impeller I can think of where a 2D approach would be useful. And in this case it is a normal rotating frame of reference. I have no idea where a translating GGI comes into it.

Glenn Horrocks
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Old   September 9, 2008, 08:39
Default Re: Translating mesh interface in cfx11.0 ?
  #5
Sam
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Glen,

I am studying the action of a gust on a 2d turbine stage. We want to do this in 2d because we need a quick turnaround. There is a stator row and a rotor row. The rotor row translates with respect to the stator row. Other than placing the mesh at a large radius and imposing a rotation, I dont believe there is any other way to do this in cfx. In fluent, this problem is very easily done as is.

In more general terms, there is no option in cfx for 2 meshes to translate with respect to each other. Only rotational motion between meshes is supported.

Sam.
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Old   September 9, 2008, 23:04
Default Re: Translating mesh interface in cfx11.0 ?
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Glenn Horrocks
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Hi,

I see what you are trying to do now.

This should work fine with GGIs, I have done similar things myself. You will have to define the translation using moving mesh. This will slow the simulation down somewhat as moving mesh stuff is significantly more work than RFR stuff but as it is 2D it still should be fairly quick.

Glenn Horrocks
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