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[ANSYS Meshing] Combining Turbogrid and ICEM

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Old   November 10, 2011, 10:13
Default Combining Turbogrid and ICEM
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Tom Elson
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Hi,

I'm looking to model an open rotor blade (so twisted from hub to tip) whilst fully resolving the boundary layer.

Do any of you know how feasbible it would be to create a structured grid around the blade in Turbogrid, then export the mesh the into ICEM. Then build an unstructured mesh in ICEM, and merge the two?

The plan would be to have fully strucutred mesh around the blade with a 50% span tip clearence (created in Turbogrid), then have unstrucutred mesh (created in ICEM) completing the domain out to the radial farifield.

Any other possible solutions would be welcome too.


Thanks

Tom
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Old   November 10, 2011, 10:18
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If you want to create interface between upper portion of tip clearance (half tip clearance gap and casing) with other half portion of tip clearance (with complete blade blade, hub) then there is no need to go to ICEM. This can be done easily in CFX Pre. So in other words

1. create mesh of blade with half tip clearance including hub and blade in turbogrid
2. Create mesh of other half tip clearance in ICEM
3. Take both meshes to CFX Pre and create interface between them (GGI)
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Old   November 10, 2011, 10:23
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Ah I see what you mean. Thanks for the suggestion.

I am hoping to use Fluent, but in theory could switch to CFX if needed.

However, I chose 50 % span tip clearence as thats as large as I could create in Turbogrid. For the open rotor simulation, looking to have farfield boundary at least 6 chords in the radial (vertical along blade) direction.

The reasoning would be, a good quality structured grid created in TG to resolve the local flow features around the blade (wake and vortices etc) then unstructured to extend out to the far-field to resemble the unducted (open rotor) flow physics.
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Old   November 10, 2011, 10:25
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No need to use CFX. Can be combined in Fluent as well
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Old   November 10, 2011, 15:23
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Ah ok, do you think doing the merging of the two meshes in ICEM would produce any difference in quality?

The GGI in CFX-pre does look quite handy. I'm just concerned about having interface problems between the two meshes. And ensuring complete periodicity between the two.

In the long run, this method should save time though.
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Old   November 10, 2011, 15:28
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Quote:
I'm just concerned about having interface problems between the two meshes. And ensuring complete periodicity between the two.
THere should be no problem with interface, these methods are well tested and have wide acceptance. there shouldn't be any problem of periodicity, cause you are just making interface at internal boundary.

Quote:
Ah ok, do you think doing the merging of the two meshes in ICEM would produce any difference in quality?
you inner domain is in rotating reference frame and outer domain in stationary domain. So it is normal practice to mesh them separately and no need to merge them in ICEM
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Old   November 10, 2011, 15:42
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Ah that makes sense.

But I was planning on having the entire domian as stationary. And setting the fluid to rotate. Will look into having rot and stat domains. Which in theory makes more sense.

I'd presume Fluent has similar capabilities with GGI to CFX.

Thanks for the continued feedback,

Its very helpful!
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Old   November 10, 2011, 15:50
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Quote:
But I was planning on having the entire domian as stationary. And setting the fluid to rotate.
When you make the fluid rotating, it is called rotating reference frame (rotating domain)
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Old   November 10, 2011, 15:53
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Ye, but you can also have the entire fluid domain rotating, and solve in the absolute frame. This avoids having high relative velocities at the boundaries.

But, having an inner rotating domain and stationary outer, will also have same effect I believe.
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Old   November 11, 2011, 02:53
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Make sure to put the

1. For Fluent : Outer domain boundaries (except inlet and outlet) with zero rpm in absolute reference frame with appropriate axis of rotation.

2. For CFX : Outer domain boundaries (except inlet and outlet) as counter rotating wall
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Old   June 21, 2012, 17:13
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Dear Far

I need to Mesh inside my blade. I am creating my grid with turbogrid. but I have problem to creat the mesh of blade. I am exporting the Mesh of Turbogrid to Gambit to do that work. Also because of the grid at the tip, I can not export the grid to pointwise.
Could you please give me some suggestion?

Best
Mahdi
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Old   July 7, 2012, 13:24
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do you still need help?
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Old   July 7, 2012, 13:44
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Quote:
Originally Posted by Far View Post
do you still need help?
Dear Far

Thanks for reply. I have created the tip clearnce in Bladegen and exported in pointwise to make the grid. but still I have problem. If there would be a way for fast creation of Rotor grid and also a grid inside a blade it will be really helpful.

But I need a Grid which is generated ( for example turbogrid ) to be readable in Pointwise. I nead to creat two block very thin along the surface of the blade to test a boundary layer control technique.

In Fact my future problem will also be refining the mesh around those blocks because of the imposed grid scale of physiscs of the problem.

If you could give some advise i will grateful

best
Mahdi
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