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[DesignModeler] Extracting fluid domain for a compressor

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Old   February 4, 2014, 08:14
Default Extracting fluid domain for a compressor
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Hello all,

I'm modelling a flow through a compressor, and I'm essentially looking to extract the passage of fluid between two adjacent blades to investigate the behavior as it gets compressed. I don't know how many of you here use CREO 1.0 for modelling, but still please do provide your inputs on this. I have made the model in CREO and to create the fluid domain, I used a "boundary blend" over the blade edges, after which I used the "merge" option, and finally "solidify". I got a good shape for the fluid domain, but when I slice it in the mesher, all I can see is a hollow shape (with no cells in the interior). I don't understand where I went wrong, I thought the "solidify" option was supposed to fill the bound volume with material.

Also I did not prefer to do this in Design Modeller because the I didn't find the "fill" option that friendly, and also not many tutorials were available to get a good understanding of the command.

So I'd be really happy if you could suggest a good way to extract the fluid domain and also mesh it, as I haven't been able to discover one. Thanks !
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Old   February 5, 2014, 02:42
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Any ideas people?
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Old   February 5, 2014, 06:25
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Never mind people, I got it ! Silly mistake I must say, while exporting the model from CREO, I hadn't chosen to export it in "solid" form. It was being exported by default in "surfaces" form, and hence, the hollow object in Meshing. However, the extracting the fluid region in CREO wasn't exactly easy for me, still managed it. It would've probably been easier using the "fill" command in DesignModeler though (again, provided I had exported it in "solid" form; this also explains why the "fill" command gave errors in DesignModeler).

I'll post if I encounter issues in meshing and so on. Thanks !
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Old   June 1, 2015, 08:58
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Hi Supermanks,
Greetings.

I know its been a while since you posted on this thread but I found this similar to the problem I am facing.
I am trying to extract the fluid region of an compressor using "fill" option but it isn't working for me.
I am using fill by caps and have capped the inlet, outlet and bearing housing (shaft hole) but it isn't working. Any inputs on what am doing wrong or any other effective way to extract the fluid domain.
Thank you.
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Old   June 2, 2015, 01:25
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Hi Sidharath,

I modeled the compressor in CREO 1.0, and using commands such as "boundary blend", "solidify", I was able to extract the fluid domain in CREO itself, which then I exported to design modeler without hassle. However, this method is very primitive, and by no means a convenient and general one to apply to different blade geometries.

However, the easier way to go about this is to use Blademodeler and Turbogrid for modeling the passages and meshing them with good quality hex mesh.

Hope this helps!

Regards
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Old   June 2, 2015, 05:20
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Thanks for the prompt reply Supermanks
What I am planning to do is modeling the stationary mesh as unstructured & rotating mesh as structured.
I have .stp file of compressor and I am trying to get the stationary fluid volume in design modeler using "fill" option and for rotating part I am trying to use the FLowPath option but sadly none of them is working out as of now.
In the details of FlowPath, the "Number of Layers" is frozen to 0 and i can't seem to change it. If I try to generate the flowpath, its now working and i am getting this error "Error: Failed to generate because of invalid property/properties
Context: ansFClientBMBladeDesign::Execute FlowPath1"

Any ideas on this one would be great for me. Thank you.
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Old   June 2, 2015, 06:22
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One point you need to clarify is the "stationary/rotating" mesh you are talking about. Is your analysis going to be a transient one? If not, then you do not require moving meshes. Additionally, when you talk about rotating and stationary components, do you mean that you will be modeling the volute as well (assuming that yours is a centrifugal compressor)? You might want to consider whether taking the stator/volute into the picture is something you really require for the problem.

Also, I'm not familiar with using the 'fill' option for the extraction in case of turbomachinery, as I've had little success myself, and hence cannot answer your doubts on that. As I've said before, alternative paths would be to model in other CAD software and extract and import the fluid domain into the mesher OR to create the blade geometry in Bladegen and generate the mesh in Turbogrid, the latter option being the obvious choice for many for modeling rotating geometries (as I've attempted both).

One more suggestion: You would do well to create a fresh post regarding your issue.
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Old   June 2, 2015, 08:54
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Thank you again for your inputs.
The simulation would be a steady state one for now but end objective includes transient response that why i am protecting it for transient too. But for now I am trying to:
-Stationary parts (volute, extended inlet & outlet) to be meshed in ansys mesher and i suppose that will be an unstructured mesh. From he compressor .stp file, I am first deleting the wheel, then capping the model and then trying to use fill for getting fluid domain. Fill didn't work for me and if the problem persists, i will move back to cad tool and export directly the fluid domain to be used in Ansys mesher.
- Rotating part (rotor/wheel) to be meshed in Turbogrid. From the compressor .stp file, i am trying to extract the flowpath and other blade editor data in design modeler for getting a Turbo grid mesh (structured).
I was wondering if there is any way to replicate the blade geometry in bladegen from cad data (.stp) ?
I am just starting on Turbo-machinery analysis and quite new to ansys and cfd, so there are chances my questions might come across as very stupid ones
I have started a thread few hours back on PathLine error, still awaiting the replies from users
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Old   June 3, 2015, 02:07
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For extracting the fluid domain for the volute casing, once you have capped all ends, afaik the fill command should work well. Perhaps you could check if your face selections for 'fill' are complete, or check if its an issue with your geometry itself.

You really don't need to export the model to Turbogrid, since you can as easily model it in Bladegen and transfer it to the mesher. I don't think you can import a model into Bladegen as .stp, but there might be an option for you to import the model as a .csv file or something similar. Then do check if your CAD software allows you to export it in that format.

Regards
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Old   June 4, 2015, 06:02
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I am using "fill" in similar fashion. I have used "cap" over 4 surfaces viz. compressor inlet , volute outlet and compressor wheel & bottom slot (the compressor wheel I am using has bottom and top slots for shaft and nut respectively). Strangely using fill I am getting only 1 solid surface and that is the solid cylinder inside the wheel top and bottom cap but if I delete the wheel and then use "fill" using 2 caps (inlet and outlet of compressor), I am getting the complete fluid domain.

Regarding Bladegen, I've no control over the blade modeling as I am not the one modeling it and .stp file is my only input and I am expected to work with it. Under these constraints I am trying to work my way through using designmodeler to model the passage flowpath and then using bladeset export point to model wheel in Turbogrid.
So far I haven't made any success, If you have any suggestionsplease share them. I would let you know once I am able to get a approach to work this way.
Thanks
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Old   June 4, 2015, 07:23
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You could maybe post a picture of your model; will make it easier for others to suggest ways.

Regarding Bladegen, what do you mean by you don't have control over the modeling? Surely you must be knowing the design parameters such as blade angles, radii, airfoil profiles etc? Bladegen requires you to be familiar with certain terminology/definitions, and I've no sources with me right now to share. Dig around the forum and web, and you should be able to find some. Though it might take some time for you to familiarize, IMO it is the quickest way to get things done.
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Old   June 8, 2015, 11:14
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Hi Supermanks,
Apologies for delayed reply, i had limited internet connectivity.
I am able to achieve the stationary mesh (volute and inlet) through Ansys mesher and I have successfully got the rotor mesh file from turbogrid (with some smalls problems in mesh quality).
I am now setting up the problem in CFX-Pre. The problem am facing now is the re-circulation slow interface in CFX. I need to create a separate boundary on shroud region to match the re-circulation slot on static mesh. I am not sure how to do this in CFX-pre or even if this has/can be done in cfx-pre at all. Any inputs ?
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