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

pressure ratio simpleFoam boundary case/0/p

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 2, 2009, 08:43
Default pressure ratio simpleFoam boundary case/0/p
  #1
New Member
 
Join Date: May 2009
Posts: 14
Rep Power: 17
Hasselhoff is on a distinguished road
Hi Folks!

I'm trying to calculate the inlet pressure of a test element, which represents a stepped seal labyrinth of a turboengine.This actually looks quite similar to a pipe (one Volume, inlet, outlet, wall).
I want to compare these pressure results with experimental data files.
The solver I use is simpleFoam, the velocity at the inlet is 10.4546m/s, the outlet pressure is constant (1bar)

my problem seems to be very simple, but I'm struggling real hard with the boundary conditions in 0/p..
Due to the dimensions (N/mē), I also set the internalField + outlet value 1e5, but in that case, no velocity profile was visualized and the pressure values were not realistic. It should be a pressure ratio (inlet- outlet) of 1.07
Paraview shows negative pressure values, if I use the following configuration:

dimensions [0 2 -2 0 0 0 0];

internalField uniform 0;

boundaryField
{
outlet
{
type fixedValue;
value uniform 0;

}
wand
{
type zeroGradient;

}
inlet
{
type zeroGradient;

}
}



The 0/U looks like:


dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
outlet
{
type zeroGradient;

}
wand
{
type fixedValue;
value uniform (0 0 0);

}
inlet
{
type fixedValue;
value uniform (10.4546 0 0);
}
}

Can u help me with this? If you know any case where I can see how it's done please let me know. I couldn't find anything..

thank u,

Mitch
Hasselhoff is offline   Reply With Quote

Old   June 2, 2009, 09:12
Default
  #2
Senior Member
 
dmoroian's Avatar
 
Dragos
Join Date: Mar 2009
Posts: 648
Rep Power: 20
dmoroian is on a distinguished road
Hello Mitch,
Due to the fact that you're using an incompressible flow solver, the pressure dimension is not N/m2 but m2/s2 (the pressure is divided by the density). Moreover, the computed value of the pressure is a relative one (p_calculated = p-p_reference) so there is no unphysical behavior if you get negative pressures, it just means that the absolute pressure happens to be smaller than the reference pressure you wrote in the dictionary.

I hope this is helpful,
Dragos
dmoroian is offline   Reply With Quote

Old   June 29, 2009, 19:43
Default
  #3
New Member
 
Join Date: May 2009
Posts: 14
Rep Power: 17
Hasselhoff is on a distinguished road
Thanks for the answer. You're right, I didn't consider that..

Hasselhoff is offline   Reply With Quote

Reply

Tags
boundary condition, pipe, pressure ratio, simplefoam, velocity inlet


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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pressure boundary condition C-H Kuo Main CFD Forum 18 September 16, 2016 04:19
Pressure Inlet Boundary Condition Prasad FLUENT 6 April 9, 2013 22:32
How to give pressure boundary condition in SIMPLER algorithm shyamprasad Main CFD Forum 0 March 17, 2009 00:40
correct UDF code for unsteady pressure boundary James W FLUENT 0 November 2, 2005 12:38
may I use Pressure inlet Boundary as free surface? duci FLUENT 0 August 23, 2002 23:29


All times are GMT -4. The time now is 11:16.