Pressure outlet

Klavoir · September 29, 2021, 05:31

Hi,

In my simple case, I have a pipe with at the end 4 branches. I want to calculate the pressure drops in the system. I want to specify a mass flow inlet.
Can I specify 4 outflow boundary conditions at the exits? Or should I use one pressure outlet at an exit (with zero pressure) and 3 outflow boundary conditions so that there is gauge pressure defined somewhere in the domain? If I dont have any pressure outlet defined it seems Fluent doesn't know the absolute pressure level anywhere?

LuckyTran · September 29, 2021, 16:46

It depends...

You shouldn't need an absolute pressure to even be able to use any outflow BCs in the first place.

But if you are using a massflow inlet BC in a compressible problem where pressure matters, then you can use four pressure outlets with targeted mass flow rate option and no outflow BCs at all.

September 29, 2021, 05:31	Pressure outlet	#1
Klavoir New Member Join Date: Sep 2021 Posts: 22 Rep Power: 4	Hi, In my simple case, I have a pipe with at the end 4 branches. I want to calculate the pressure drops in the system. I want to specify a mass flow inlet. Can I specify 4 outflow boundary conditions at the exits? Or should I use one pressure outlet at an exit (with zero pressure) and 3 outflow boundary conditions so that there is gauge pressure defined somewhere in the domain? If I dont have any pressure outlet defined it seems Fluent doesn't know the absolute pressure level anywhere?

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September 29, 2021, 16:46		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	It depends... You shouldn't need an absolute pressure to even be able to use any outflow BCs in the first place. But if you are using a massflow inlet BC in a compressible problem where pressure matters, then you can use four pressure outlets with targeted mass flow rate option and no outflow BCs at all.