CFD Online Discussion Forums

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   FLUENT (https://www.cfd-online.com/Forums/fluent/)
-   -   what is meant by Operating Pressure in Fluent? (https://www.cfd-online.com/Forums/fluent/114329-what-meant-operating-pressure-fluent.html)

mifrah March 9, 2013 04:51

what is meant by Operating Pressure in Fluent?
 
hello all,
i am a new user in Fluent.
i want to know what exactly is meant by operating pressure in fluent?
its default value is 101325 pa, is it atmospheric pressure? but sometime we also assume 0 as operating pressure, its making me feel dizzy....
what will be the operating pressure in 10 meter depth of a pool?
:confused:

blackmask March 9, 2013 06:40

It depends on how you model the density. It is always valid to set the operating pressure to (approximately) the mean pressure of the flow field. But it is only when you model the density using incompressible ideal gas law, or you are dealing with low-Mach-number compressible flow that the value of operating pressure is important.

The operating pressure is not used if the density is modeled to be constant.

You should check the Fluent user manual because it has more detailed and accurate description of the operating pressure.

mifrah March 9, 2013 13:38

in my case density is constant so it means i can take operating pressure as zero??????

farzadpourfattah March 9, 2013 16:16

dear ....
 
when you set pressure of operation condition 0 pascal, you prevent reverse flow in your domain.

blackmask March 10, 2013 02:15

Yes. You can set operating pressure to any value because it is not used in case of constant density.

mifrah March 12, 2013 15:02

Thank you :rolleyes:

flow_CH June 8, 2013 12:13

what is that value in VOF model? (water+air)

farzadpourfattah June 15, 2013 11:27

vof
 
if you set value of water 1 in a zone,value of air will be 0 at same zone.

rizkydjonhansemit June 6, 2016 12:57

Quote:

Originally Posted by blackmask (Post 412696)
It depends on how you model the density. It is always valid to set the operating pressure to (approximately) the mean pressure of the flow field. But it is only when you model the density using incompressible ideal gas law, or you are dealing with low-Mach-number compressible flow that the value of operating pressure is important.

The operating pressure is not used if the density is modeled to be constant.

You should check the Fluent user manual because it has more detailed and accurate description of the operating pressure.


hi blackmask,
can you tell us how do we know the mean pressure of the flow field in fluent. in my case i simulate 2d vawt in a wind tunnel. is there any consideration when we want to specify certain value of operating condition in fluent for incompressible ideal gas air. what about reference pressure location? its default value is [0,0,0]. how to specify the right reference pressure location in our simulation? please help us

rizkydjonhansemit June 12, 2016 17:49

is there any help?

paragmangave September 20, 2017 00:07

Quote:

Originally Posted by blackmask (Post 412696)
It depends on how you model the density. It is always valid to set the operating pressure to (approximately) the mean pressure of the flow field. But it is only when you model the density using incompressible ideal gas law, or you are dealing with low-Mach-number compressible flow that the value of operating pressure is important.

The operating pressure is not used if the density is modeled to be constant.

You should check the Fluent user manual because it has more detailed and accurate description of the operating pressure.

i am trying to simulate flow over blunt bodies my conditions are 100500pa, 303k,1.1551 density, what should be my operating pressure and guage pressure?

pakk September 20, 2017 09:01

You choose!

Real pressure = operating pressure + guage pressure.

If you want the real pressure to be 100500 Pa, you can set operating pressure at 100500 Pa, and then at the boundary set 0 Pa.
Or set the operating pressure at 100000 Pa, and the pressure at the boundary at 500 Pa.
Or the operating pressure at 0 Pa, and the pressure at the boundary at 100500 Pa.

Physically, it is all the same. Exactly the same, identical.

Only numerically, it is helpful to have smaller numbers for guage pressures, so put your operating pressure close to the 'average' pressure in your system. Extreme example: don't set your operating pressure at 10000100500 Pa, and your guage pressure at -10000000000 Pa, you will get numerical problems.

paragmangave September 20, 2017 09:11

Also is prism layer generation necessary for supersonic speed?.
Without using prism layer mesh can I use k omega or k epsilon turbulence model?


All times are GMT -4. The time now is 14:09.