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

Ueqn.A() extract the diag. term from the Ueqn??

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

Like Tree1Likes
  • 1 Post By Martin80

Reply
 
LinkBack Thread Tools Display Modes
Old   July 2, 2013, 23:19
Default Ueqn.A() extract the diag. term from the Ueqn??
  #1
Senior Member
 
Dongyue Li
Join Date: Jun 2012
Location: Torino, Italy
Posts: 676
Rep Power: 8
sharonyue is on a distinguished road
I just made a testify, add this code into icoFoam:
Code:
fvVectorMatrix UEqn
        (
            fvm::ddt(U)
          + fvm::div(phi, U)
          - fvm::laplacian(nu, U)
        );

Info<<"UEqn:" << UEqn << endl;
Info<<"UEqn.A():" << UEqn.A()<< endl;
Info<<"UEqn.H():" << UEqn.H()<< endl;        
        //solve(UEqn == -fvc::grad(p));

        // --- PISO loop
Then I run a 9 nodes cavity case. It output this in the first timestep:
Code:
Create time

Create mesh for time = 0

Reading transportProperties

Reading field p

Reading field U

Reading/calculating face flux field phi


Starting time loop

Time = 0.005

Courant Number mean: 0 max: 0
UEqn:Lower triangle = 
12
(
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
)


diagonal = 9(0.00012 0.00015 0.00012 0.00015 0.00018 0.00015 0.00012 0.00015 0.00012)

Upper triangle = 
12
(
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
-3e-05
)



[0 4 -2 0 0 0 0]
9{(0 0 0)}

3
(
3((6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05))
9((6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05) (6e-05 6e-05 6e-05))
0()
)


3
(
3((6e-05 0 0) (6e-05 0 0) (6e-05 0 0))
9{(0 0 0)}
0()
)


UEqn.A():dimensions      [0 0 -1 0 0 0 0];

internalField   nonuniform List<scalar> 9(800 700 800 700 600 700 800 700 800);

boundaryField
{
    movingWall
    {
        type            zeroGradient;
    }
    fixedWalls
    {
        type            zeroGradient;
    }
    frontAndBack
    {
        type            empty;
    }
}

UEqn.H():dimensions      [0 1 -2 0 0 0 0];

internalField   nonuniform List<vector> 9((0 0 0) (0 0 0) (0 0 0) (0 0 0) (0 0 0) (0 0 0) (200 0 0) (200 0 0) (200 0 0));

boundaryField
{
    movingWall
    {
        type            zeroGradient;
    }
    fixedWalls
    {
        type            zeroGradient;
    }
    frontAndBack
    {
        type            empty;
    }
}
So in this log, Why Ueqn.A()'s internal field is not equal to the Ueqn's diag. term? I mark this two in the red.

Thanks in advance,
sharonyue is offline   Reply With Quote

Old   July 4, 2013, 05:40
Default
  #2
Senior Member
 
Dongyue Li
Join Date: Jun 2012
Location: Torino, Italy
Posts: 676
Rep Power: 8
sharonyue is on a distinguished road
If A()=diag()/mesh.V(),
this is my mesh:

Code:
convertToMeters 0.03;

vertices
(
    (0 0 0)
    (1 0 0)
    (1 1 0)
    (0 1 0)
    (0 0 0.1)
    (1 0 0.1)
    (1 1 0.1)
    (0 1 0.1)
);

blocks
(
    hex (0 1 2 3 4 5 6 7) (3 3 1) simpleGrading (1 1 1)
);
So V is 0.003*0.01*0.01=0.000003.
but 0.00012/0.000003 does not equal to 800.
sharonyue is offline   Reply With Quote

Old   July 24, 2013, 11:08
Default
  #3
Member
 
Join Date: Aug 2010
Posts: 31
Rep Power: 7
Martin80 is on a distinguished road
Hi,

Ueqn.A()=diag()/mesh.V() holds true only for cells, which do not contact the boundary. E.g. in your example:

600=0.00018/(0.01*0.01*0.003)

[and be careful mesh.V()=3e-7 (not 3e-6)].

At the moment I'm also trying to clarify details about the "Ueqn.A()".

B.r. Martin.
sharonyue likes this.
Martin80 is offline   Reply With Quote

Old   July 24, 2013, 11:12
Default
  #4
Senior Member
 
Dongyue Li
Join Date: Jun 2012
Location: Torino, Italy
Posts: 676
Rep Power: 8
sharonyue is on a distinguished road
Quote:
Originally Posted by Martin80 View Post
Hi,

Ueqn.A()=diag()/mesh.V() holds true only for cells, which do not contact the boundary. E.g. in your example:

600=0.00018/(0.01*0.01*0.003)

[and be careful mesh.V()=3e-7 (not 3e-6)].

At the moment I'm also trying to clarify details about the "Ueqn.A()".

B.r. Martin.
So this is only true for inner cells, not boundary cells. Thats clear! Thx very much!
sharonyue 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
adding dispersion force term in UEqn leads to oscillations of velocity field sr_tenedor OpenFOAM Programming & Development 2 June 6, 2014 06:59
Adding an explicit source term in the UEqn() Anne Lincke OpenFOAM Running, Solving & CFD 0 June 25, 2013 12:19
Source term problem in UEqn of simpleFoam fisch OpenFOAM Programming & Development 1 June 17, 2011 10:57
Extract momentum source term Rickard.Solsjo OpenFOAM 0 January 14, 2011 10:44
ATTENTION! Reliability problems in CFX 5.7 Joseph CFX 14 April 20, 2010 15:45


All times are GMT -4. The time now is 15:51.