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IGES to ICEM CFDtoCFX problem. Please help

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Old   January 3, 2004, 22:50
Default IGES to ICEM CFDtoCFX problem. Please help
  #1
Melisa
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Hi everyone,

When I import my IGES file to ICEM CFDtoCFX and measure the size of my geometry, I realise that the scale is not right.

I never have this problem when I import this file to CFXBuild and other CAD software.

Anyone know the reasons? Please tell me. Thank you!
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Old   January 3, 2004, 22:55
Default I'm confused with the units used
  #2
Melisa
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What is the unit used in ICEM CFDtoCFX? I can hardly trace & redraw my geometry right now.

Please help me. Thank you!
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Old   January 4, 2004, 08:42
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #3
Amit
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hi Melisa,

In CFX build you have the geometry dimensions in numbers with one specified unit of length. Whenever you use show option in build, it just shows that number. But the main geometry units are defined in Cfx-pre and that is only used finally for getting solution. So taking care in cfx-pre will help you.

hope your problem gets resolved.

Amit Katiyar
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Old   January 4, 2004, 11:02
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #4
Melisa
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Hi Amit,

Thanks for your reply but I suppose you're talking about the CFX-pre, not ICEM CFDtoCFX....I don't have this problem when using build or CFX-pre.

However, when I import the IGES geometry to ICEM CFDtoCFX, it just show me some rediculous dimension. The shape is right though. I have no idea how to repair my geometry when I need to redraw a curve or a surface in ICEM CFDtoCFX.

Please help, guys.
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Old   January 4, 2004, 11:51
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #5
Amit
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hi melisa,

You are right that I am talking about CFX build and pre thinking that you have a similar kind of problem. I am sorry I can't suggest any thing specifically when you import the IGES geometry to ICEM CFDtoCFX.

Bye Amit
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Old   January 4, 2004, 17:49
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #6
Glenn Horrocks
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Hi Melisa,

Use Geometry/Transform/Scale in ICEM CFD 4.CFX to rescale the size of your geometry to the correct units. You can scale all the points, curves and surfaces this way.

Glenn
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Old   January 4, 2004, 19:11
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #7
Derrek
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All:

I did some testing and it appears that ICEM4CFX assigns a unit system differently for the various CAD systems. Below is what I found.

I wrote out IGES files for two different CAD systems to test.

100mm in Pro/E comes across as a 100 units in ICEM4CFX

100in in Pro/E comes across as ~2540 units in ICEM4CFX (implying that the units are getting converted to mm)

100mm in SW comes across as 100 units in ICEM4CFX

100in in SW comes across as 100 units in ICEM4CFX

I am not sure I know what to expect for IGES files. I didn't think there was any standard unit system, rather it took on the active system within the CAD system.

Parasolid files, however, write out in meters. Does anyone else have more on this?

Regards,

Derrek
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Old   January 4, 2004, 20:41
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #8
Melisa
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Thanks, Derrek.....

At least I know I'm not alone here.

I'm using CADKEY V20. 100mm in CADKEY comes across as ~2540 units in ICEM4CFX

Can anyone suggest a way to get it right?

Thank you.
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Old   January 4, 2004, 20:48
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #9
Melisa
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Thanks, Glenn...

I will try this but I can hardly get the exact scaling factor as I can only measure the distance approximately in the ICEM CFDtoCFX.

Anyone has any idea about the scaling factor?

Thanks again for your help, guys.
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Old   January 4, 2004, 21:50
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #10
Derrek
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Look at the values you are getting, ~2540, correct? So if you divide by 25.4 you will get the desired 100 units. In ICEM4CFX, you would use the Scale command under the Transformation Tools and enter a scaling factor of 1/25.4 for all three directions.

Derrek
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Old   January 4, 2004, 23:36
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #11
Jeff
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I had the same problem with STEP files. It seems that ICEM-CFD-4.CFX thinks that these files are imported in units of inches. It then proceeds to convert them to mm. by multiplying everything by 25.4. Why it would assume you "wanted" everything in mm is beyond me, but that's what I'm seeing.

The previous suggestion to scale by 1/25.4 is the appropriate one.
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Old   January 6, 2004, 20:37
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #12
Melisa
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Thank you, Amit,Glenn,Derrek & Jeff. My problem seems to be solved.
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Old   January 7, 2004, 00:37
Default Re: IGES to ICEM CFDtoCFX problem. Please help
  #13
Angel
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Hi Melisa,

in addition to Glenn's remarks

get the geometry into cfx-pre and scale it by 1/25.4 instead of 3.93700787401574803149606299212e-2 Round-off error can be avoided if you type 1/25.4 as the scale factor.

does this help?

Angel
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