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

Pressure inlet BC

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 1, 2010, 10:29
Question Pressure inlet BC
  #1
New Member
 
Join Date: Dec 2010
Posts: 2
Rep Power: 0
vallet is on a distinguished road
Hi,
I'm a new openfoam user. I think my problem has already been discussed, but I didn't know why my calculation doesn't work...
I simulate a laminar flow between two "wavy" surfaces and I want apply a pressure BC at inlet and outlet.

So I use the following options :
for U:
boundaryField
{
inlet
{
type pressureInletVelocity;
value uniform (0 0 0);
}

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

outlet
{
type zeroGradient;
}
}

and for p:
boundaryField
{
inlet
{
type fixedValue;
value uniform 10;
}

wall
{
type zeroGradient;
}

outlet
{
type fixedValue;
value uniform 0;
}
}

Whatever the time step, calculations don't converge (the courant number increases after several iterations). I use the icoFoam solver.
vallet is offline   Reply With Quote

Old   December 2, 2010, 03:24
Default
  #2
Member
 
Masashi Ohbuchi
Join Date: Oct 2009
Posts: 74
Rep Power: 16
Ohbuchi is on a distinguished road
Hi,
I've also tested for tutorial "icoFoam/elbow" with modifying boundary condition as follows.

0/U file
velocity-inlet-5
{
type pressureInletVelocity;
value uniform (1 0 0);
}

0/p file
velocity-inlet-5
{
type fixedValue;
value uniform 10;
}

And the simulation was completed and no error.
I suppose the problem might be elsewhere, such as fvSolution.
Ohbuchi is offline   Reply With Quote

Old   December 2, 2010, 07:36
Default
  #3
Senior Member
 
Nakul
Join Date: Apr 2010
Location: India
Posts: 147
Rep Power: 15
nakul is on a distinguished road
Hi,
I think that maybe your flux value should not be zero at inlet. Some finite velocity might be required at inlet.

If this is not the case then you may post your case here in order to get proper advice.
nakul is offline   Reply With Quote

Old   December 2, 2010, 08:11
Default
  #4
Member
 
Masashi Ohbuchi
Join Date: Oct 2009
Posts: 74
Rep Power: 16
Ohbuchi is on a distinguished road
I've tried again with following settings,

0/U

velocity-inlet-5
{
type pressureInletVelocity;
value uniform (0 0 0);
}

But, no error was occurred.
Ohbuchi is offline   Reply With Quote

Old   December 2, 2010, 08:17
Default
  #5
Member
 
Cedric Van Holsbeke
Join Date: Dec 2009
Location: Belgium
Posts: 81
Rep Power: 16
CedricVH is on a distinguished road
You have fixed static pressures at inlet and outlet. This is physically impossible.

At the inlet, you need a apply a total pressure (totalPressure boundary condition) and at the outlet a static pressure (fixedValue).
CedricVH is offline   Reply With Quote

Old   December 2, 2010, 12:39
Default
  #6
New Member
 
Join Date: Dec 2010
Posts: 2
Rep Power: 0
vallet is on a distinguished road
thanks for your replies.

Cedric, I don't see why a static pressure is not physical. If we consider an infinite pressurized vessels at inlet ?

If I apply a totalPressure at inlet, calculations converge but I don't have a constant static pressure. Moreover, results are little bit strange. I have a negative pressure p at inlet...

I'd like to have a constant pressure at inlet and at outlet to identify a darcy like law : q=k*(p_inlet - p_outlet), q being the mass flow rate and k a constant.

I don't really understand how the totalPressure BC work. Can you give me the meaning of all the parameters :

{
type totalPressure;
p0 uniform 1e3;
U U;
rho none;
psi none;
gamma 1;
value uniform 1e3;
}

thanks
vallet is offline   Reply With Quote

Reply

Tags
boundary conditions, icofoam, pressure inlet

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
"Pressure Inlet" Boundary Setup Wijaya FLUENT 15 May 18, 2016 11:08
Pressure Inlet Boundary Condition Prasad FLUENT 6 April 9, 2013 22:32
How to give pressure inlet in Fluent Vijayaragavan FLUENT 2 December 13, 2007 04:21
about pressure inlet boundary Sastry(CFD Forum) FLUENT 0 February 19, 2007 03:55
Neumann pressure BC and velocity field Antech Main CFD Forum 0 April 25, 2006 03:15


All times are GMT -4. The time now is 23:09.