How to create vacuum pressure on outlet?

kkragelj · January 20, 2020, 05:40

Hello.

I have a model with 2 inlets (air, turbulent flow, 2 m/s, 360°C) and 2 outlets. How do I set the pressure on outlets - vacuum pressure of 200 Pa?

Thanks!

Untitled.jpg

LuckyTran · January 20, 2020, 13:13

If you've already got a mesh and you're actually in Fluent, it's as simple as going to boundary conditions, selecting the outlets, setting the type as pressure outlets and specifying a pressure of -200 Pa. The real question is where are you currently at?

kkragelj · January 22, 2020, 02:09

Quote:

Originally Posted by LuckyTran

If you've already got a mesh and you're actually in Fluent, it's as simple as going to boundary conditions, selecting the outlets, setting the type as pressure outlets and specifying a pressure of -200 Pa. The real question is where are you currently at?

I figured it out myself, thanks anyway!

random_ran · January 24, 2020, 14:31

Does it mean that once the pressuer is below 101,325 Pa, it is then considered that the region is vacuum?

AlexanderZ · January 27, 2020, 06:40

Quote:

Originally Posted by random_ran

Does it mean that once the pressuer is below 101,325 Pa, it is then considered that the region is vacuum?

what is vacuum? from your point of view

random_ran · January 27, 2020, 10:11

Quote:

Originally Posted by AlexanderZ

what is vacuum? from your point of view

Some people say vacuum refers to any space in which the pressure is
considerably lower than atmospheric pressure.

I think that we should focus on the density not pressure.

"Whenever the density of gas in a given volume is reduced below that
corresponding to the density of atmospheric gas at ground level, a
vacuum is obtained. "

- G. F. Weston Ultrahigh Vacuum Practice.

For example, when the air flow pass a circular cylinder, there is a low
pressure area in the leeward side fo the cylinder. How can you say that
the recirculation zoon (low pressure are) is vacuum due to pressure is
lower than the other part?

January 20, 2020, 05:40	How to create vacuum pressure on outlet?	#1
kkragelj New Member Kristjan Kragelj Join Date: Jan 2020 Posts: 3 Rep Power: 6	Hello. I have a model with 2 inlets (air, turbulent flow, 2 m/s, 360°C) and 2 outlets. How do I set the pressure on outlets - vacuum pressure of 200 Pa? Thanks! Untitled.jpg

January 24, 2020, 14:31		#4
random_ran Member Ran Join Date: Aug 2016 Posts: 69 Rep Power: 10	Does it mean that once the pressuer is below 101,325 Pa, it is then considered that the region is vacuum? __________________ Yours in CFD, Ran

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January 20, 2020, 13:13		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,750 Rep Power: 66	If you've already got a mesh and you're actually in Fluent, it's as simple as going to boundary conditions, selecting the outlets, setting the type as pressure outlets and specifying a pressure of -200 Pa. The real question is where are you currently at?