CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

pressure in function of time

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   February 4, 2011, 04:58
Default pressure in function of time
  #1
New Member
 
Rafał Kryjak
Join Date: Jul 2010
Posts: 11
Rep Power: 6
dzuodoka is on a distinguished road
Here is the thing:

I have transient flow with CHT through the pipe. Pressure and temperature are in function of time and when it's coming to change parameter of pressure then appears a problem with overflow and temperature has been clipped.

For being more clear:

from 0 s to 480 s pressure equals 14.7 psi
from 481 to 520 s pressure equals 56.4 psi
and so on ....

the problem appears in solver from 450 s
time step 30 s

any advice ?
dzuodoka is offline   Reply With Quote

Old   February 4, 2011, 05:12
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 9,551
Rep Power: 76
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
You will have to give more details if we are to help. Is the flow compressible? Show a drawing of the geometry.
ghorrocks is offline   Reply With Quote

Old   February 4, 2011, 05:45
Default
  #3
New Member
 
Rafał Kryjak
Join Date: Jul 2010
Posts: 11
Rep Power: 6
dzuodoka is on a distinguished road
Flow is compressible.
Turbulence model SST.

dzuodoka is offline   Reply With Quote

Old   February 4, 2011, 05:58
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 9,551
Rep Power: 76
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Can you explain your diagram? I do not know what it means.
ghorrocks is offline   Reply With Quote

Old   February 4, 2011, 07:03
Default
  #5
New Member
 
Rafał Kryjak
Join Date: Jul 2010
Posts: 11
Rep Power: 6
dzuodoka is on a distinguished road
It's the pipe connection with closing wall inside (no flow through this wall only CHT). My aim is to find out what is the change temperature on this wall depening on time. I got three boundary conditions and after three hours the mass flow outlet is opened and I wrote expressions including pressure, temperature and mass flow in function of time. The problem appears in the simulation when the parameters are changed.

Function of pressure:
dzuodoka is offline   Reply With Quote

Old   February 5, 2011, 05:05
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 9,551
Rep Power: 76
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
You are probably getting transient compressible flow stuff happening, like shock waves due to the rapid pressure changes. I would round the pressure history off to be more realistic.

I still have no idea what you are trying to model.
ghorrocks is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
TimeVaryingMappedFixedValue irishdave OpenFOAM Running, Solving & CFD 26 July 24, 2014 04:30
calculation diverge after continue to run zhajingjing OpenFOAM 0 April 28, 2010 04:35
latest OpenFOAM-1.6.x from git failed to compile phsieh2005 OpenFOAM Bugs 25 February 9, 2010 04:37
Convergence moving mesh lr103476 OpenFOAM Running, Solving & CFD 30 November 19, 2007 14:09
Hydrostatic pressure in 2-phase flow modeling (long) DS & HB Main CFD Forum 0 January 8, 2000 15:00


All times are GMT -4. The time now is 17:27.