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Old   November 26, 2012, 07:40
Default Time Step Continuity
  #1
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Matthias
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Hi,

I am new to OpenFoam and I try to simulate a axisymmetric flow. My result doesn't look very useful in the paraviewer. By solving with the icoFoam-solver I get the following message (here the last time step):


Code:
Time = 0.6

Courant Number mean: 2.23e+34 max: 5.65961e+37
DILUPBiCG:  Solving for Ux, Initial residual = 0.998035, Final residual = 6.06503e+07, No Iterations 1001
DILUPBiCG:  Solving for Uy, Initial residual = 0.902429, Final residual = 8.16874, No Iterations 1001
DILUPBiCG:  Solving for Uz, Initial residual = 0.997655, Final residual = 2.25247, No Iterations 1001
DICPCG:  Solving for p, Initial residual = 1, Final residual = 18.6765, No Iterations 1001
time step continuity errors : sum local = 6.55952e+47, global = -8.33417e+31, cumulative = -8.33417e+31
DICPCG:  Solving for p, Initial residual = 0.998855, Final residual = 7.59938, No Iterations 1001
time step continuity errors : sum local = 4.59185e+51, global = -4.68485e+35, cumulative = -4.68568e+35
ExecutionTime = 38.21 s  ClockTime = 39 s
Can somebody help me?
Thank you!!
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Old   November 27, 2012, 04:48
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ATM
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Hi,

There is a serious problem in your case setup because the Courant number

Code:
 Courant Number mean: 2.23e+34 max: 5.65961e+37
Can never , ever be so high. You are not implementing the right BCs.
What case are you trying to simulate?

Regards,

A.T.M
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Old   December 2, 2012, 06:45
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Zifei Yin
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Please do checkMesh before calculation, probably there are some mesh problems. Also, reduce the time-step to see if there is any changes.
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Old   December 3, 2012, 07:03
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Matthias
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the blockMesh:

Code:
convertToMeters 0.001;

vertices
(
    (0 0 0)           // 0 Bottom
    (88 3.0730 0)     // 1 Bottom
    (88 3.0730 2)     // 2      Top
    (0 0 2)           // 3      Top
    (88 -3.0730 0)    // 4 Bottom
    (88 -3.0730 2)    // 5      Top
    (32.5 -1.134925 2)// 6      Top
    (32.5 1.134925 2) // 7      Top
    (32.5 1.134925 0) // 8 Bottom
    (32.5 -1.134925 0)// 9 Bottom
    (62.5 -2.1825 0)  //10 Bottom
    (62.5  2.1825 0)  //11 Bottom
    (0 0 1)           //12   Mid
    (32.5 1.134925 1) //13   Mid
    (32.5 -1.134925 1)//14   Mid
    (62.5 -2.1825 1)  //15   Mid
    (62.5 2.1825 1)   //16   Mid
    (88 -3.0730 1)    //17   Mid
    (88 3.0730 1)     //18   Mid
    (62.5 2.1825 2)   //19      Top
    (62.5 -2.1825 2)  //20      Top
);

blocks
(
   // hex (0 9 8 0 3 6 7 3) (20 20 20) simpleGrading (1 1 1)       //wedge
   // hex (8 9 4 1 7 6 5 2) (20 20 20) simpleGrading (1 1 1)       //wholeBlock

    hex (0 9 8 0 12 14 13 12) (50 50 50) simpleGrading (0.1 1 10)    //wedgeBottom       0
    hex (12 14 13 12 3 6 7 3) (50 50 50) simpleGrading (0.1 1 0.1)  //wedgeTop          1
    hex (9 10 11 8 14 15 16 13) (50 50 50) simpleGrading (10 1 10)    //   midBottom    2
    hex (14 15 16 13 6 20 19 7) (50 50 50) simpleGrading (10 1 0.1)  //   midTop                3
    hex (10 4 1 11 15 17 18 16) (50 50 50) simpleGrading (0.1 1 10)  //      outBottom  4
    hex (15 17 18 16 20 5 2 19) (50 50 50) simpleGrading (0.1 1 0.1)//      outTop      5
);

edges
(
);
boundary
(

front
     {
           type wedge;
           faces
           (
               (0 8 13 12)
               (12 13 7 3)
           );
      }

back
     {
           type wedge;
           faces
           (
               (0 12 14 9)
               (12 3 6 14)
           );
      }

tankWall
     {
           type wall;
           faces
           (
               (1 4 17 18)
               (18 17 5 2)
           );
      }

bottomWall
     {
           type wall;
           faces
           (
               (0 9 8 0)
               (8 9 10 11)
               (11 10 4 1)
           );
      }
rotatingPlate
     {
           type wall;
           faces
           (
               (3 7 6 3)
           );
      }

openFluid
     {
           type patch;
           faces
           (
               (7 19 20 6)
               (19 2 5 20)
               (9 14 15 10)
               (10 15 17 4)
               (14 6 20 15)
               (15 20 5 17)
               (11 1 18 16)
               (8 11 16 13)
               (16 18 2 19)
               (13 16 19 7)
           );
      }

axis
     {
           type empty;
           faces
           (
               (0 12 12 0)
               (12 3 3 12)
           );
      }
);


mergePatchPairs
(
);
checkMesh tells me this:

Code:
Build  : 2.1.1-221db2718bbb
Exec   : checkMesh
Date   : Dec 03 2012
Time   : 12:00:30
Host   : "lstma243"
PID    : 25757
Case   : /tmp/OpenFOAM/matthias-2.1.1/tutorials/incompressible/icoFoam/cavity
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMas                                                                                        ter
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           772751
    faces:            2272500
    internal faces:   2222500
    cells:            750000
    boundary patches: 7
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     745000
    prisms:        5000
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     0

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
    Patch               Faces    Points   Surface topology
    front               5000     5151     ok (non-closed singly connected)
    back                5000     5151     ok (non-closed singly connected)
    tankWall            5000     5151     ok (non-closed singly connected)
    bottomWall          7500     7651     ok (non-closed singly connected)
    rotatingPlate       2500     2551     ok (non-closed singly connected)
    openFluid           25000    25351    ok (non-closed singly connected)
    axis                0        0        ok (empty)

Checking geometry...
    Overall domain bounding box (0 -0.003073 0) (0.088 0.003073 0.002)
    Mesh (non-empty, non-wedge) directions (1 0 1)
    Mesh (non-empty) directions (1 1 1)
    Wedge front with angle 2 degrees
    Wedge back with angle 2 degrees
 ***Number of edges not aligned with or perpendicular to non-empty directions: 7                                                                                        47400
  <<Writing 747703 points on non-aligned edges to set nonAlignedEdges
    Boundary openness (1.20325e-17 -9.40901e-17 3.47075e-15) OK.
    Max cell openness = 1.23591e-15 OK.
    Max aspect ratio = 296.346 OK.
    Minumum face area = 1.16905e-11. Maximum face area = 1.31286e-07.  Face area                                                                                         magnitudes OK.
    Min volume = 9.64031e-15. Max volume = 6.66225e-12.  Total volume = 5.40846e                                                                                        -07.  Cell volumes OK.
    Mesh non-orthogonality Max: 1.96008 average: 0.932908
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.333336 OK.
    Coupled point location match (average 0) OK.

Failed 1 mesh checks.

End
I tried several timesteps (until 2e-6) but the error always got too big...

Last edited by hiasl; December 3, 2012 at 07:41.
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