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Parametric run - Pressure Transfer Function

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Old   October 9, 2013, 08:58
Default Parametric run - Pressure Transfer Function
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Hi all!

I'm working on a pipline analysis(transient simulation).
My goal is to get the Pressure Transfer Function of my pipeline system (Pout/Pin in frequency range).

My input is something like this: Mass Flow=100*sin(fi*2*pi*t), where fi is parametric with range 50[Hz]-100[Hz], with 0.2[Hz] step.

I can make it manualy with CFD-Post-->Chart-->FFT-->Export but i don't want to do this 100* time..
I want to automatize this process as much as i can.
Sadly i don't have Matlab in our office.

If you have any suggestion i would like to hear it.

Thank you in advance,
Janos
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Old   October 9, 2013, 09:32
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Hi Janosch,

i would try using Workbench for this. You just set your fi as an input parameter in CFX-pre and create different design points by varying it according to your step size.

I dont know what exactly the Pressure transfer function is. But maybe it is possible to calculate the significant parameters in this function by CEL and then set those as output parameters. This way you would have all the results in one design point table in workbench and you could simply copy and paste them into excel or wherever you want them.
If you really need all the data from the Chart, there is probably a way to automatically export the chart data for every design point created in workbench. But I can't give you any advice on how to do that exactly.
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Old   October 9, 2013, 10:39
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Hi Murx!

Thank you for your fast reply.
I'm thinking of using Workbench as you suggested.
I have a theory to make this, but i dont know how to use "cfx5mondata".

If i could make a script to write out monitor points as .csv in each frequency i could use them in microsoft excel and with a VB script i would be able to get my Transfer Equation, because excel can make fourier transformation.
I dont't know how to implement "cfx5mondata" to write a .csv file with each parameter value.

I have an other way in mind also:
In Workbench i can only get constans as output variable, this is why i have to export the whole simulation into a new Workbench project for each Design Point. I can make a session file about writing time dependent pressures out, but i dont't know how to reply this for each .res file(which i will have for each Design Point) automaticly.
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Old   October 9, 2013, 17:41
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Glenn Horrocks
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* You can automate CFD-Post with session files.
* If you don't have matlab then try octave or python with numpy or scipy. They can do this analysis as well and they are open source.
* You do not need to use cfx5mondata. You can just export the data from the solver manage by right clicking on the chart of the data you wish to export.
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Old   October 11, 2013, 04:00
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Hi ghorrocks!

Thanks for the tips about numpy or scipy.

I know that i can export monitor points manualy by right click, but i started this topic because i don't know how to do it automaticly.
I have more than 100 parametric value, i don't want to open every single model and export input and output pressure curve.

Same for Session. I don't know how to write a do loop to automaticly run the session file from the first result file until the 100th and write every time my curves with different names.
Maybe you can give me a hint how to do this?

Thank you in advance,
Janos
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Old   October 11, 2013, 06:42
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Automatic - then use cfx5mondata. Look it up in the documentation for how to use it, or cfx5mondata -help.

The easiest way to start in session files is just to record one of doing an example propst processing and look at the file. The syntax is pretty simple.
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