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Old   August 16, 2006, 05:45
Default Obtain Geometry Data from a Grid File in CFX 10.0
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Dear Friends,

Resently, I was given an old grid file for a compressor stage (Rotor and Stator). I need to use this file for further work. Unfortunately, I cannot use it because of the following reasons:

1) It has a coarse GRID. 2) I have no control over the GRID, since I have no CFXTG input files (Profile.curve / Shroud.curve / Hub.curve) 3) It was build using the old TascFlow tool thus I have only the .BCF and .Grd files

I was wondering if we could obtain the geometry information for the hub.curve / shroud.curve and 10 blade section profile.curve from the grid file I have.

Basically, I need the 3 curve files from the grid file. Mainly, how could I get "10" section profile data for the blade, from base of the blade (hub region) all the way up to the tip of the blade (shroud region)?

Can this be done in CFX 10.0 Post / CFX 10.0 Pre?

I would be obliged if any one please give me the steps I need to follow as I am pretty new to CFD.

This particular grid file works fine as it is giving me good convergence and results. Will it give the same results if I recreate the grid back, using the geometry data extracted from this file? or would it be close to it? How about effects on convergence?

Thanking you all in advance.

Best regards, Arjun

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Old   August 16, 2006, 08:51
Default Re: Obtain Geometry Data from a Grid File in CFX 1
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If you are lucky, then when you read in the result into cfx5post, appropriate regions were written to the grd file when they were created (hub, shroud, blade, etc.)

if not, it could be difficult. When you read in a TASCflow job, a Block I, J, K is created of the structured grid. Hopefully, at least your K is along the spanwise direction and you can create an ISOSURFACE of Block K to slice through the model along a constant k plane.

If not, then you will need to create planes to intersect the surface. Polyline from Boundary Intersection. boundary will be the surface and intersect with the plane you create.

Also, if you do happen to know the grd regions and IJK structure, you can manually create a gci file with the regions and when you read in the rso, the gci regions will also be created. But this requires a working knowledge of the regions in the grd file.

Once you have what you need, it is easy enough to export the xyz coordinates in CFX post.

Or, you can contact Ansys-CFX customer support and see if you can send them the geometry and they can then read it into TASCflow and rsf export the xyz for the surfaces/profiles you need. Maybe free or at a nominal fee, shrug. Or find someone with a TASCflow license.

I am on a mission to convince Ansys-CFX to at least create a full featured TASCflow reader such that CFX Post can understand a structured grid, grd regions as seen in TASCflow, and create regions on said structured grid. That would be so nice. Even if it was an external program that would at least allow me to read in the grd file and create the necessary regions for the CFX turbo and write those regions back to the grd file (this would be for cases where the grd file did not have the appropriate regions written to the grd file).

If someone knows something easier/better I am up for the lesson. We are keeping a set of tascflow licenses around just for this problem.
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Old   August 17, 2006, 07:20
Default Re: Obtain Geometry Data from a Grid File in CFX 1
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Dear Michael,

Thank you very much for the solution. I shall give it a go and hope I am successful 1st time.

Thanking you once again.

Best regards, Arjun
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