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gardian October 6, 2010 09:08

Reference Pressure
 
Hello
I m trying to simulate the Helium 3 behavior in a long low temperature tube.
i m heating the ends and run a steady state simulation.
the results agrees with the experimental values. I estimate the distribution of number of moles for a specific pressure.

question : can i set the reference pressure in a specific point?" (x,y, z )
why i receive a warning like the pressure has not be set at any domain?
so CFX set it somewhere zero ?

thank you

michael_owen October 6, 2010 15:15

Yes, CFX is setting the relative pressure to zero at node 0 I believe, because the pressure level is not set by the boundary conditions. This is probably fine for your simulation. The variation in the pressure throughout the domain is probably extremely small compared to you reference pressure. You don't need to worry about it. But if you want, you can explicitly set it on the Advanced Options tab of the Solver Controls (Pressure Level Information).

gardian October 6, 2010 15:26

Reference Pressure
 
Thanks

i have done this in the Advanced Option in the Solver control.
I receive the same warning : pressure has not been set at any domain.
and after CFX sets a zero pressure somewhere but not close to the specific point.

what about the Relative Pressure Level? should be zero or my value?

michael_owen October 6, 2010 16:18

Quote:

Originally Posted by gardian (Post 278158)
Thanks

i have done this in the Advanced Option in the Solver control.
I receive the same warning : pressure has not been set at any domain.
and after CFX sets a zero pressure somewhere but not close to the specific point.

what about the Relative Pressure Level? should be zero or my value?

You probably left it set to Automatic, which is what it does anyway. If you want to force it, switch Automatic to Cartesian Coordinates, specify the location, and set the Relative Pressure Level. Most likely you will set it to 0, since it is relative to the Reference Pressure you set in the Domain definition.

gardian October 7, 2010 09:04

Quote:

Originally Posted by michael_owen (Post 278163)
You probably left it set to Automatic, which is what it does anyway. If you want to force it, switch Automatic to Cartesian Coordinates, specify the location, and set the Relative Pressure Level. Most likely you will set it to 0, since it is relative to the Reference Pressure you set in the Domain definition.


I wish it was like this .. but I ve already set as you correctly say the Coordinates .. The same message always appears.

gardian October 7, 2010 12:09

Hello
another question in this subject is : if i rotate the tube and set the pressure this setting doesn't include the Hydrostatic effect. is it possible to set a pressure that should include it?

michael_owen October 7, 2010 14:30

Quote:

Originally Posted by gardian (Post 278282)
I wish it was like this .. but I ve already set as you correctly say the Coordinates .. The same message always appears.

What is the exact warning message?

gardian October 8, 2010 04:00

Hello
I always set the reference position at ( 10, 0,0 ) .
This is the message I receive:



| Reference Pressure Information |
+--------------------------------------------------------------------+

Domain Group: CB IN

Pressure has not been set at any boundary conditions.
The pressure will be set to 0.00000E+00 at the following location:
Domain : MRB IN
Node : 9472 (equation 530280)
Coordinates : (-1.03395E+04, 2.56102E+00, 4.70348E+00).

Domain Group: CB IN

Buoyancy has been activated. The absolute pressure will include
hydrostatic pressure contribution, using the following reference
coordinates: (-1.51400E+03, 1.04840E+04,-5.00000E+00).

gardian October 8, 2010 04:03

but my main physical problem is the following :
when I tilt this tube ( not rotation, just changing the gravity vectors )
the real pressure should be the Absolute Pressure cause my sensor is where the gas is accumulated .
But i can set only the reference Pressure or CFX thinks that this is the real pressure?
what I m thinking wrong?
maybe I have to post another thread .


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