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How to calculate pressure drop

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Old   March 8, 2010, 08:34
Default How to calculate pressure drop
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Jérémy Bulle
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Hello,

I have a channel solved with simplefoam and I would like to calculate the pressure drop ... How can I do that?

Thanks for the help
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Old   March 8, 2010, 09:28
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Andre Z
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Hi,
after the calculations you have you calculate the total pressure.
Then you should calculate the average over the boundaries you are analyzing. I do not know how to automatically calculate the difference using openfoam utilities, so you will either have to write your own program to do this or use your calculator (or brain).
Here are the commands you need:
Code:
ptot
patchAverage ptot inlet
patchAverage ptot outlet
I assumed you named our boundaries "inlet" and "outlet".
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Old   March 8, 2010, 10:01
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Jérémy Bulle
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Ok!!

Thanks a lot for the help
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Old   March 10, 2010, 11:37
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Jérémy Bulle
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How does the patchAverage utily work? Is it mass flow weighted? Area weighted?

Thanks for the information
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Old   March 11, 2010, 04:00
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Andre Z
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I am not sure.
but as far as I know the massflow is the phi-field. When you execute yPlus it calculates phi. When you execute patchAverage it does not. So I think one can say that the patchAverage utility does not use the massflow.

You could take a look into the source code. I do not have the time for that right now but it should be easy to understand.
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Old   March 11, 2010, 04:34
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Andre Z
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Ok,
I took a look.
Its averaged over the area.
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Old   March 13, 2010, 07:44
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Jérémy Bulle
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A big big thanks for the help!!
I've found something interesting on the wiki :

http://openfoamwiki.net/index.php/Co...unctionObjects

But I can't make it work. I don't know how to use it. Maybe I have to run the case to make it work and you cannot use a command tu run it after solving the problem ...
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Old   March 15, 2010, 04:01
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Andre Z
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Hi,
that does sound very interesting indeed.
I will check it out later today.
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