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[GAMBIT] Nozzle/Rotor design Gas Turbine (Using turbo)

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Old   June 20, 2013, 06:40
Default Nozzle/Rotor design Gas Turbine (Using turbo)
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Hello,

Currently I'm doing my Master thesis about the fluid behavior through an Axial Gas Micro Turbine and I'm trying to reproduce one physic prototipe (with its specific parameters) using Gambit (Geometry and Mesh). I'm following the tutorial "Basic Turbo Model with Unstructured Mesh" since I need to represent in 3D the model and generate in 2D the surface in order to study the changes of differents parametres through the rotor and the stator.

The problem is when I generate the turbo and I want to define to control volume appears that message

"ERROR: ACIS error 8030: inconsistent face-body relationships. A valid flow volume could not be constructed. Ensure that a valid turbo profile has been constructed with mean edges and hub and casing edges. Geometric modifications of this data, including vertex slides or edge repositioning, may be required for a succesful flow volume construction."

Of course I understand the message but I don't already know what more can I try to do. Any idea?

BTW: In the beginning I had one problem that shows this message: "Ensure all blades/splitter section tip vertices are connected to only 2 edges" and, only for it useful for someone, that means that it is impossible to use turbo model if each vertex has associated more than two edges, i.e., take care if you have something hidden. That was my mystake.

PS: I attached the pictures of what I want to do/get and the step where I have the problem with the error mentioned above (mine and the same steps of tutorial). My last picture it seems that Gambit generate the volume control but it is only a Screenshot, automatically then disapears.TutTurbo.jpg

TurboMine.jpg

2D model.jpg

3D model.jpg
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Old   June 20, 2013, 08:15
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First I never used Turbo in Gambit, and I don't have it.
In your step 3 from your 2nd picture, I see surfaces displayed with green edges, but I also see yellow edges which I would delete, since they are not usefull.
So in visibility icone, choose surface, and select your surfaces. Enable visibility off and apply.
The surfaces should disappear and only yelow edges should remain. Then select them and delete.
Display all surfaces again, and you should have 3surfaces, which represent your fluid domain.
Enable shaded mode on, and the airfoil should appear as hollow, which is correct.
You should be able to mesh the surfaces.
PS: I don't know why you have 3 surfaces, but if they are here for the BL, you can apply a BL without needing to define them as surfaces (in 2d they will be attached to edges)
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Old   June 20, 2013, 09:11
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Hi -mAx-,

Thank you for your quick reply. Maybe you misunderstood something or I explained in a wrong way. The question is that the third picture you refer I can never get it, since the software start to generate it but suddendly appears the error, and I obtain again the second picture (automatically generates the previous step). This third picture is only a screenshot during the proces of generation that never is done.

Thank you.
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Old   June 20, 2013, 09:31
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I am refering on the 2nd picture: turbomine.jpg (step 3)
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Old   June 20, 2013, 09:37
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Yes yes me too. I understood what you told me, but the yellow edges automatically disappear if the third step is done it successfully, but not is my case. From two step to three one the software try to generate it (the step 3) but appear the error, and I can never complete this last step. I don't know if I explain properly.
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Old   June 20, 2013, 09:40
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ok, can you display your geometry before the error occures
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Old   June 20, 2013, 09:45
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Yes of course, I can. Is the second image in picture 2.
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Old   June 20, 2013, 09:58
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ok,
then you just have to construct your domain manually.
You need basically to construct the top and bottom splines, which are the same, since (I assume), they will be treated as periodic. Their locations are also fixed because of periodicity.
The spline is already generated by turbo, and is the brown one located in the middle of your foil.
So copy this edge once with specified y-translation, and again in -y direction.
Then do some splits for closing your domain and you will be able to create first surface (don't create foil surface now).
Once it is done, go and create surface foil.
Now substract first surface with foil's surface.
That's it, you have your domain
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Old   June 20, 2013, 10:37
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Ok, I've tried to do it but the problem is that the revolution is copied as well...
Look the image.
Attached Images
File Type: jpg TurboProblem.jpg (69.6 KB, 28 views)
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Old   June 21, 2013, 00:58
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delete the revolution
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Old   June 23, 2013, 13:34
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Quote:
"ERROR: ACIS error 8030: inconsistent face-body relationships. A valid flow volume could not be constructed. Ensure that a valid turbo profile has been constructed with mean edges and hub and casing edges. Geometric modifications of this data, including vertex slides or edge repositioning, may be required for a succesful flow volume construction."
This message shows either you have problem in turbo file .tur or settings in Gambit.
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Old   June 24, 2013, 05:19
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-mAx-

Sorry for the delay. So, finally I could delete the other revolutions (I needed first to unlink the camber line to the revolution and then convert them in real edges) but, done this, new problems arise.

#1. There are no volumes containing both inlet and outlet faces. (Intuitively, then, I generated a volume with the entire control volume, which contains intlet and outlet faces)

but, done that..

#2. An axis of revolution con't be determined from the inlet face.

Far

Thank you for the information, but sincerely I don't know what I should to do for solve the problem (I am not a good knowledgeable of this software yet)

Anyway, thank you to both. For me it does not matter whether I do manually, or automatically, but of course it is interesting to learn both ways.

I attached a picture of what I got manually.as.jpg
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Old   June 24, 2013, 05:24
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wait do you want 2d or 3d domain?
I thought you wanted 2d
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Old   June 24, 2013, 05:31
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Ok, maybe I realized that I might be a little confused. My idea is to simulate in 2D, as it is shown in the picture you have attached, but at the same time I'd like to generate in 3D the prototipe, without the intention to use it in the simulation.

So, I'm doing in a wrong way perhaps?
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Old   June 24, 2013, 06:03
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you can still extrude the 2d domain for having 3d (sweep function)
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Old   June 24, 2013, 06:42
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Sorry mAx I didn't undersand what you tried to told me..
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Old   June 24, 2013, 07:04
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2d domain is a surface.
If you extrude this surface in the third direction you get a volume (gambit function for that is "sweep face")
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Old   June 24, 2013, 08:39
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If you need 2d geometry then you there is no need of using turbo function. Simply import coordinates of airfoil, make a curve passing through mid of airfoil (not necessarily follow the camber line).

Extend that curve to required inlet and outlet locations (typically it is 1 chord upstream and 1.5 chord downstream).

copy that curve one both sides of airfoil by 1/2 * pitch.

Make inlet and outlet curve.

Make face from inlet, outlet and two periodic curves. Make another face for airfoil. Subtract inner face from outer face and you will get fluid region.

Apply mesh settings and export and read into Fluent.
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Old   June 24, 2013, 09:39
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-mAx

Uooh! Thank you, I didn't know this way to generate depht. It's so greatl!

Far

Ok, thank you very much.

If both of you don't mind, I have mroe questions (Let's hope so).

1) To create the limit edges in order to design the same structure that shows the picture added by mAx some anwers before, Have I to create manually those boundaries (both stator and rotor) and then import them into fluent or is some automatically function/option?

2) To activate the option that the rotor blades get moving and then simulate/evaluate what happen, for instance, with temperature through the set, this is in fluent right?

3) Then... Have I to create the blade cascade in Gambit and then export to Fluent or using this last one there is an option to duplicate your blades (either rotor or stator)?

4) Is it possible to export to fluent two diferent geometries (since rotor and stator blades are differents) comming from two diferents gambit files? (To create the same layout that the image before)

Thank you to both. Is very useful your help.
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Old   June 24, 2013, 09:48
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1) you have to import them in Fluent, but watch out in the picture it seems to be sliding mesh (Far should correct me). That means you will import 2 separated fluid domain with 2 interfaces (one interface per domain)

2) Yes in fluent. Far should tell me more about sliding mesh /SRF / MRF (I only know sliding mesh)

3) Periodicity should help http://aerojet.engr.ucdavis.edu/flue...ug/node389.htm
Far is experienced in this area

4) yes it is: http://aerojet.engr.ucdavis.edu/flue...e171.htm#20871
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