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-   -   Internal flow operating condition? (http://www.cfd-online.com/Forums/fluent/137762-internal-flow-operating-condition.html)

kookguy June 22, 2014 21:28

Internal flow operating condition?
 
Hi,

I am trying to simulate an internal swirl flow (compressible) in a cylindrical duct. I know the inlet boundary condition (flow speed/ pressure/ rotation speed etc.) and I assume 1 atm pressure outlet. I also realize that my (default) operating condition is set to 1 atm. Once I changed the operating condition, the axial velocity (simulation result) of the flow changes according to the new operating pressure, as if the operating condition is the bulk static pressure for my entire fluid domain.

Now my problem is that I don't know what I suppose to set the operating condition to because I actually don't know the static pressure of the flow inside of the duct. My understanding is that once I have the inlet and outlet conditions, what happens in the middle of the flow should adjust accordingly. Having to set the operating condition for internal flows confuses me. If you can help, could you suggest what I should do with the operating condition in this case? And if I change the operating condition, what does this physically represent /or how would it interact with the pressure I initially set at the inlet ? :confused::confused::confused:

Thank you very much!

samy90 June 24, 2014 02:31

hello
as i know , you must define your boundary conditions with respect to your operating condition. so when you change your operating condition, you must do the same on boundary condition, because :
absolute pressure ( what we have in real ) = operating pressure ( what we guess about flow ) + gauge pressure ( what you use in your boundary condition settings)

kookguy June 26, 2014 00:15

Thank you so much. That explanation helps a lot. :)


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