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Old   October 6, 2010, 09:08
Default Reference Pressure
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anton.gardi
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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
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Old   October 6, 2010, 15:15
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Michael P. Owen
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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).
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Old   October 6, 2010, 15:26
Default Reference Pressure
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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?
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Old   October 6, 2010, 16:18
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Michael P. Owen
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Quote:
Originally Posted by gardian View Post
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.
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Old   October 7, 2010, 09:04
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anton.gardi
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Quote:
Originally Posted by michael_owen View Post
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.
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Old   October 7, 2010, 12:09
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anton.gardi
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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?
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Old   October 7, 2010, 14:30
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Quote:
Originally Posted by gardian View Post
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?
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Old   October 8, 2010, 04:00
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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).
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Old   October 8, 2010, 04:03
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anton.gardi
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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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