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

Pressure definition in OF 2.0.1 (simpleFoam etc.)

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 27, 2011, 12:46
Default Pressure definition in OF 2.0.1 (simpleFoam etc.)
  #1
Member
 
Miles
Join Date: Sep 2011
Posts: 48
Rep Power: 5
miles_davis is on a distinguished road
Hi,
Does anyone know what is pressure in OF2.0.1 for solver like SimpleFOAM?

I have read that in previous versions of the code it was in fact Pstatic-rho*g*h, than in another version it was just Pstatic/rho. What is the actual statement for OF 2.0.1?

The source of my question is simple: Consider a water box. you model inlet and outlet.
If the outlet is at the bottom (i.e.altitude is lower than the inlet) what BC do I define for pressure at the outlet???
If P stands for p/rho, I have to calculate the hydrostatic pressure at he bottom.
If p stands fo p/rho-g*h: I just have to put P=0.

Thanks for you help.

Regards,

Miles

P.S;: I have found post on the subject but it was for older version as OF 1.7
miles_davis is offline   Reply With Quote

Old   September 28, 2011, 15:25
Default
  #2
Senior Member
 
chegdan's Avatar
 
Daniel P. Combest
Join Date: Mar 2009
Location: St. Louis, USA
Posts: 538
Rep Power: 18
chegdan will become famous soon enough
Quote:
Originally Posted by miles_davis View Post
Hi,
Does anyone know what is pressure in OF2.0.1 for solver like SimpleFOAM?

I have read that in previous versions of the code it was in fact Pstatic-rho*g*h, than in another version it was just Pstatic/rho. What is the actual statement for OF 2.0.1?

The source of my question is simple: Consider a water box. you model inlet and outlet.
If the outlet is at the bottom (i.e.altitude is lower than the inlet) what BC do I define for pressure at the outlet???
If P stands for p/rho, I have to calculate the hydrostatic pressure at he bottom.
If p stands fo p/rho-g*h: I just have to put P=0.

Thanks for you help.

Regards,

Miles

P.S;: I have found post on the subject but it was for older version as OF 1.7
Miles,

For simpleFoam it is a relative pressure related to a reference value. If you look at the creatFields.H and Peqn.H in the simpleFoam solver that might help.

Dan
chegdan is offline   Reply With Quote

Old   September 28, 2011, 17:16
Default
  #3
Senior Member
 
Vesselin Krastev
Join Date: Jan 2010
Location: University of Tor Vergata, Rome
Posts: 361
Rep Power: 10
vkrastev is on a distinguished road
You are confusing compressible and incompressible solvers. As far as I know, all the incompressible solvers in OF (like simpleFoam or pisoFoam), in all the releases (at least from the 1.6 to the 2.0.1, including the -dev/-ext ones), solve for the kinematic relative pressure, i. e. for p/rho (if rho is a constant, defining the pressure source term in the momentum equation as -1/rho*grad(p) or as -grad(p/rho) is equivalent). For the compressible solvers, things are not so established between different releases (honestly i really can't understand why), as for example in the 1.6 release a solver like rhoSimpleFoam assumes the static pressure as the dependent variable, while in the 1.7.0/1/x (and I think also in the 2.0.0/1/x family) the dependent variable is p-rho*g*h.

Hope this helps

V.
vkrastev is offline   Reply With Quote

Old   September 29, 2011, 18:35
Default
  #4
Member
 
Miles
Join Date: Sep 2011
Posts: 48
Rep Power: 5
miles_davis is on a distinguished road
thanks for your replies

regards

miles
miles_davis 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
BC settings to expand pressure on atmosphere - simpleFoam / totalPressure sErik OpenFOAM Running, Solving & CFD 1 June 15, 2011 02:49
Setup/monitor points of pressure and force coefficients siw CFX 3 October 22, 2010 06:07
pressure in incompressible solvers e.g. simpleFoam chrizzl OpenFOAM Running, Solving & CFD 7 August 24, 2010 11:19
Neumann pressure BC and velocity field Antech Main CFD Forum 0 April 25, 2006 02:15
Pressure definition CFX Begineer CFX 4 October 18, 2002 11:31


All times are GMT -4. The time now is 10:48.