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Evacuate Vacuum Chamber

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Old   July 21, 2016, 08:27
Question Evacuate Vacuum Chamber
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Hello Everybody,

is it possible to simulate a chamber with just an outlet to see how the pressure changes by evacuating the chamber with a pump?

I know the mass flow at the outlet. But when i say there is a specific Outlet mass flow the simulation got an error in the X-momentum.

Is it even possible, because simply say i take mass out of the chamber so the density and pressure changes. How can i do that? Or is it impossible due to mass imbalances? Iīm not afraid of UDF if itīs necessary.

I hope you understand what i wanted to explain, my English is not the best.
As Fluid i use air.

Kind regards
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Old   July 21, 2016, 09:02
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When i use velocity at outlet, no pressure change occurs.

What else can i try?
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Old   July 22, 2016, 03:21
Default Floating Pressure
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So itīs me again.

I modeled a Volume surrounded by walls and one outlet. At the outlet i defined a mass-flow-inlet with my mass-flow by changing the direction vector so it flows out of the domain. Then i took air and in the material panel ideal gas for density (compressible). As operating pressure i choose floating pressure. For inital floating pressure i use 101325 Pa, my pressure at the beginning. I do transient calculation. When i start the calculation i got an error: Divergence detected in AMG solver: pressure correction.

What am i doing wrong?
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Old   June 16, 2017, 07:43
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I think that it is not necessary to use floating pressure.
Maybe you can try a high-pressure chamber and mass-flow-inlet with negative mass flow?

--
Sorry, my fault.
You could try mass-flow-inlet with negative mass flow and floating pressure since there is no pressure-referenced boundary condition.
--
The mass-flow-inlet could not be negative.
Then I suggest
1. Using floating operating pressure and mass-flow-inlet with the outward direction since the mass flow could not be negative.
2. Using velocity inlet with negative velocity and proper absolute pressure(maybe 0?).

Last edited by SJSW; June 20, 2017 at 05:15.
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Old   June 20, 2017, 01:38
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hello,
I want to simulate the process of evacuating a chamber with just an outlet in FLUENT. But I am confused about the boundary condition of the outlet. Would you give me some advice? Thank you so much!
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Old   June 20, 2017, 04:13
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What is your confusion with the boundary condition of the outlet?
Maybe you could describe it more specifically. @@
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Old   June 20, 2017, 04:57
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Because this chamber is vacuumed by the vacuum pump, the velocity and the pressure of boundary are always changing. And I want to calculate the time to reach the specified pressure in the chamber.
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evacuate, fluent, udf, vacuum, x-momentum

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