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Old   November 5, 2012, 06:37
Default CEL mathematical functions in CFD Post
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Hi guys,

I am normally a Fluent user, but an trying to do some quick post processing in CFD/CFX Post, and was wondering if any of the dyed in the wool CFX users could give me a quick helping hand?

I want to post process some data which i have not exported from my Fluent case file, but cannot seem to get CFD Post to recognise my CEL expression.

I was wondering if this was because CEL mathematical expressions are not recognised in CFD post, or perhaps my syntax is wrong? Can anyone help?

the expression is basically:

Code:
1.004*loge(Temperature)@X3-0.287*loge(Pressure)@X3
where X3 is a user created sampling plane.

As you can see, basically, I am trying to check the entropy generation calculation from my solver, but for some reason the expression is not accepted in CFD Post...

Any help from you CFX guys would be much appreciated,
best regards
Jon
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Old   November 5, 2012, 06:46
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You should get a warning that "The dimensions of the argument to function
'loge' are inconsistent".
Make the arguments dimensionless:
Code:
loge(Temperature/1[K])
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Old   November 5, 2012, 07:57
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Quote:
Originally Posted by Lance View Post
You should get a warning that "The dimensions of the argument to function
'loge' are inconsistent".
Make the arguments dimensionless:
Code:
loge(Temperature/1[K])
Hi Lance,

Thank you very much - yes, I see that now. However, I am not even getting that far ...

At the moment, i am getting the following exact error message:

Code:
ERROR
The following unrecognised name was referenced: loge.
Which is why i thought perhaps the CFX maths functions are not supported. Any ideas re: this specific error?

My exact code is:

Code:
1004*loge(Temperature/1[K])@X3 - 0.287*loge(Pressure/1[Pa])@X3
I have also tried the alias: ln

Thanks for your previous post - much appreciated
Regards
Jon
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Old   November 5, 2012, 08:13
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Sorry, I didnt look carefully at your expression. 'loge' does not accept a location (@X3). But something like:

1004*loge(Temperature/1[K]) - 0.287*loge(Pressure/1[Pa])

would create an variable. Then, go to Variables, create new variable, select your expression, then plot on your surface (or whatever you want to do with the expression/variable)
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Old   November 5, 2012, 08:16
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Ah thanks Lance - you're a champ - really appreciate that, have been tearing my hair out trying to figure out what i was doing wrong.

Much appreciated.

BTW, best reference for CEL / CCL : CFX User Guide??

CFD-Post UG seems a little thin for detail!
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Old   November 5, 2012, 08:20
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Yes, the Post guide is a bit thin about CEL, but have a look the in the CFX reference guide (cfx_ref.pdf). It has a whole chapter about CEL functions.
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Old   November 5, 2012, 08:25
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Cool, thanks lance, will check it out

Cheers
Jonathan
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Old   November 5, 2012, 09:20
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Hey thanks again Lance, this is working like a charm ... really appreciate your help today!

Cheers
Jonathan
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Old   November 5, 2012, 09:23
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That's great to hear, and I hope you didnt tear all of your hair out
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Old   November 5, 2012, 09:37
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haha, no stopped short, but nearly
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