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

The initial condition for alpha

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 3, 2014, 07:16
Default The initial condition for alpha
  #1
Member
 
Xiantao Zhang
Join Date: Nov 2014
Posts: 31
Rep Power: 12
zhxter is on a distinguished road
Dear Foamers,
Now I am trying to simulate waves using OpenFOAM.

And I have one question about the initial condition for alpha(the volume fraction)

In the 0 folder, the alpha is set as follows,
dimensions [0 0 0 0 0 0 0];

internalField uniform 0;

boundaryField
{
//- Set patchGroups for constraint patches
#include "${WM_PROJECT_DIR}/etc/caseDicts/setConstraintTypes"

movingWall
{
type zeroGradient;
}

rightWall
{
type zeroGradient;
}

bottom
{
type zeroGradient;
}

atmosphere
{
type inletOutlet;
inletValue $internalField;
value $internalField;
}

defaultFaces
{
type empty;
}
}

// ************************************************** *********************** //
The atmosphere boundary is set as inletOulet. And I look for the user guide and find that "inletOutlet" Swithes U and p between fixedValue and zeroGradient depending on direction of U . But I still don't quite understand the meaning? can anyone help me???
zhxter is offline   Reply With Quote

Old   December 3, 2014, 07:46
Default
  #2
Senior Member
 
Pablo Higuera
Join Date: Jan 2011
Location: Auckland
Posts: 627
Rep Power: 19
Phicau is on a distinguished road
Hi Xiantao,

inletOutlet is zero gradient if flow is outwards to the domain, and fixed value (equal to inletValue) otherwise.

This means that if inletValue = 0, then water and air are able to flow outside your domain through the atmosphere, but if pressure requires an entering flux, then it will only be air (alpha = 0).

Best,

Pablo
Phicau is offline   Reply With Quote

Old   December 4, 2014, 01:40
Default
  #3
Member
 
Xiantao Zhang
Join Date: Nov 2014
Posts: 31
Rep Power: 12
zhxter is on a distinguished road
Hi, Pablo

Since there are two types of data(inletValue and value) to specify for the "inletOutlet" boundary type.

You mean, if inletValue=0, then water and air are able to flow out the domain through the atmosphere boundary. inletValue corresponds to "fixedValue".

How about the second type of data "value"?? does it correspond to "zeroGradient"??

Hope to receive your reply.

Best,
Xiantao
zhxter is offline   Reply With Quote

Old   December 4, 2014, 03:33
Default
  #4
Senior Member
 
Pablo Higuera
Join Date: Jan 2011
Location: Auckland
Posts: 627
Rep Power: 19
Phicau is on a distinguished road
Hi Xiantao,

"value" is not used by OpenFOAM, it is just needed to load the case in ParaView. Sometimes when you don't specify the "value" and ParaView does not know the boundary condition it fails to load the field or crashes.

The very first time step the correct "value" is calculated by OpenFOAM.

Best,

Pablo
Phicau is offline   Reply With Quote

Reply

Tags
alpha, initial condition, inletoulet

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
problem with Min/max rho tH3f0rC3 OpenFOAM 8 July 31, 2019 10:48
conjugate heat transfer in OpenFOAM skuznet OpenFOAM Running, Solving & CFD 99 March 16, 2017 06:07
log file imani OpenFOAM Running, Solving & CFD 0 July 24, 2014 03:04
calculation stops after few time steps sivakumar OpenFOAM Running, Solving & CFD 7 March 17, 2013 07:37
Unknown error sivakumar OpenFOAM Pre-Processing 9 September 9, 2008 13:53


All times are GMT -4. The time now is 08:45.