Pressure in rhoSimpleFoam

vitor · September 16, 2010, 10:34

I'm running a simple simulation, an axial air flow through a pipe. It's compressible, with a Mach = 0,5 . I'm still setting the BC's, the problem is: which pressure I should set in the 0/p file? Is it the relative or absolute pressure?

I know that using fixedValue means that I'm setting static pressure, and totalPressure sets static+dynamic. But do I need to add the atmosferic pressure?

Let's say, if my atm pressure is 101 kPa and I want relative totalPressure @ inlet equal to 18 kPa. Then I should use 18 or 119 kPa in the 0/p file?

Thanks a lot.

Vitor

herbert · September 16, 2010, 11:03

Hi Vitor,

of course you have to define 119 kPa in your example. Atmospheric pressure is not defined elsewhere. Therfore the absolute pressure is needed to make sure that the density is calculated correctly.

Regards,
Stefan

vitor · September 16, 2010, 12:49

Indeed. I thought maybe the atmosferic pressure would be set in other file.
Thank you for your reply.

And sorry for the fundamental question...

September 16, 2010, 10:34	Pressure in rhoSimpleFoam	#1
vitor New Member Vitor Braga Join Date: Oct 2009 Posts: 28 Rep Power: 17	I'm running a simple simulation, an axial air flow through a pipe. It's compressible, with a Mach = 0,5 . I'm still setting the BC's, the problem is: which pressure I should set in the 0/p file? Is it the relative or absolute pressure? I know that using fixedValue means that I'm setting static pressure, and totalPressure sets static+dynamic. But do I need to add the atmosferic pressure? Let's say, if my atm pressure is 101 kPa and I want relative totalPressure @ inlet equal to 18 kPa. Then I should use 18 or 119 kPa in the 0/p file? Thanks a lot. Vitor

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September 16, 2010, 11:03		#2
herbert Senior Member Stefan Herbert Join Date: Dec 2009 Location: Darmstadt, Germany Posts: 129 Rep Power: 18	Hi Vitor, of course you have to define 119 kPa in your example. Atmospheric pressure is not defined elsewhere. Therfore the absolute pressure is needed to make sure that the density is calculated correctly. Regards, Stefan

September 16, 2010, 12:49		#3
vitor New Member Vitor Braga Join Date: Oct 2009 Posts: 28 Rep Power: 17	Indeed. I thought maybe the atmosferic pressure would be set in other file. Thank you for your reply. And sorry for the fundamental question...