Unstructrued O-type Mesh of a cylinder with icoFoam

kindle · December 2, 2016, 12:21

I have a poiseuille case to test on a simple cylinder. My objective is to run the T-junction case with two identical cylinders.

Depending on meshing strategy :
1. structured grid with icoFoam defaut setting of tutorial cavity:
BC
inlet : pressure value1, outlet value2 => converge
inlet : parabolic profile, outlet pressure ref=0 => converge

see butterfly.png
butterfly.png

2. O-type non-structured mesh with settings above :
BC
inlet : pressure value1, outlet value2 => diverge

Mesh looks like this :
O-type.png

checkMesh gives positive result : [tried to mesh with blockMeshDict with 6 points a hex block, that one doesn't pass the checkMesh]
High aspect ratio but low non-orthogonality, max skewness = 0.3

Code:

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

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           194481
    faces:            578400
    internal faces:   568800
    cells:            192000
    faces per cell:   5.975
    boundary patches: 3
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     187200
    prisms:        4800
    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                  
    inlet               2400     2401     ok (non-closed singly connected)  
    outlet              2400     2401     ok (non-closed singly connected)  
    walls               4800     4860     ok (non-closed singly connected)  

Checking geometry...
    Overall domain bounding box (-0.004 -0.004 0) (0.004 0.004 0.016)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (-2.77194e-17 -7.51513e-17 -4.67679e-17) OK.
    Max cell openness = 3.40144e-16 OK.
    Max aspect ratio = 38.2671 OK.
    Minimum face area = 5.22642e-10. Maximum face area = 8.37375e-08.  Face area magnitudes OK.
    Min volume = 1.04528e-13. Max volume = 8.25775e-12.  Total volume = 8.02779e-07.  Cell volumes OK.
    Mesh non-orthogonality Max: 1.70755e-06 average: 0
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.329681 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End

log :

Code:

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

Create mesh for time = 0


PISO: Operating solver in PISO mode

Reading transportProperties

Reading field p

Reading field U

Reading/calculating face flux field phi


Starting time loop

Time = 1e-05

Courant Number mean: 0 max: 0
DILUPBiCG:  Solving for Ux, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Uz, Initial residual = 1, Final residual = 4.70439e-06, No Iterations 10
DICPCG:  Solving for p, Initial residual = 1, Final residual = 8.60531e-07, No Iterations 155
time step continuity errors : sum local = 4.69332e-10, global = -3.74768e-12, cumulative = -3.74768e-12
DICPCG:  Solving for p, Initial residual = 0.0545117, Final residual = 8.84748e-07, No Iterations 138
time step continuity errors : sum local = 9.17592e-10, global = 2.54215e-12, cumulative = -1.20553e-12
ExecutionTime = 0.41 s  ClockTime = 1 s

Time = 2e-05

Courant Number mean: 0.000325844 max: 0.0219715
DILUPBiCG:  Solving for Ux, Initial residual = 0.238504, Final residual = 9.33255e-06, No Iterations 14
DILUPBiCG:  Solving for Uy, Initial residual = 0.238507, Final residual = 5.95036e-06, No Iterations 13
DILUPBiCG:  Solving for Uz, Initial residual = 0.962651, Final residual = 8.51301e-06, No Iterations 13
DICPCG:  Solving for p, Initial residual = 0.00651103, Final residual = 9.86859e-07, No Iterations 116
time step continuity errors : sum local = 9.67146e-10, global = -2.79469e-11, cumulative = -2.91524e-11
DICPCG:  Solving for p, Initial residual = 0.00214519, Final residual = 8.97386e-07, No Iterations 110
time step continuity errors : sum local = 8.75932e-10, global = -1.83468e-11, cumulative = -4.74992e-11
ExecutionTime = 0.59 s  ClockTime = 2 s

Time = 3e-05

Courant Number mean: 0.000632862 max: 0.0123958
DILUPBiCG:  Solving for Ux, Initial residual = 0.18138, Final residual = 8.22932e-06, No Iterations 15
DILUPBiCG:  Solving for Uy, Initial residual = 0.181399, Final residual = 6.14408e-06, No Iterations 15
DILUPBiCG:  Solving for Uz, Initial residual = 0.949986, Final residual = 5.35623e-06, No Iterations 13
DICPCG:  Solving for p, Initial residual = 0.007183, Final residual = 9.67958e-07, No Iterations 112
time step continuity errors : sum local = 9.47447e-10, global = -7.12456e-11, cumulative = -1.18745e-10
DICPCG:  Solving for p, Initial residual = 0.0069341, Final residual = 9.04469e-07, No Iterations 111
time step continuity errors : sum local = 8.87948e-10, global = 3.0653e-11, cumulative = -8.80917e-11
ExecutionTime = 0.79 s  ClockTime = 2 s

Time = 4e-05

Courant Number mean: 0.000939384 max: 0.0303498
DILUPBiCG:  Solving for Ux, Initial residual = 0.428115, Final residual = 7.9459e-06, No Iterations 16
DILUPBiCG:  Solving for Uy, Initial residual = 0.428095, Final residual = 5.35738e-06, No Iterations 16
DILUPBiCG:  Solving for Uz, Initial residual = 0.906008, Final residual = 5.21517e-06, No Iterations 13
DICPCG:  Solving for p, Initial residual = 0.0276355, Final residual = 8.49123e-07, No Iterations 119
time step continuity errors : sum local = 8.4924e-10, global = 1.35349e-11, cumulative = -7.45569e-11
DICPCG:  Solving for p, Initial residual = 0.0262004, Final residual = 8.13028e-07, No Iterations 118
time step continuity errors : sum local = 8.23637e-10, global = -1.30846e-11, cumulative = -8.76415e-11
ExecutionTime = 0.99 s  ClockTime = 3 s

.........
.........
.........

Time = 0.0001

Courant Number mean: 0.00791318 max: 11.8668
DILUPBiCG:  Solving for Ux, Initial residual = 0.817916, Final residual = 7.72584e-06, No Iterations 38
DILUPBiCG:  Solving for Uy, Initial residual = 0.817695, Final residual = 2.27355e-06, No Iterations 36
DILUPBiCG:  Solving for Uz, Initial residual = 0.65771, Final residual = 8.97567e-06, No Iterations 39
DICPCG:  Solving for p, Initial residual = 0.702655, Final residual = 9.289e-07, No Iterations 143
time step continuity errors : sum local = 1.72787e-08, global = 7.38884e-10, cumulative = 8.18707e-10
DICPCG:  Solving for p, Initial residual = 0.356256, Final residual = 8.647e-07, No Iterations 143
time step continuity errors : sum local = 1.70898e-08, global = 2.99532e-10, cumulative = 1.11824e-09
ExecutionTime = 2.37 s  ClockTime = 5 s

End

Finalising parallel run

p at 1st timeStep : inlet a big value at center.
p-firstTimeStep.png
p at 10th timeStep
p-10timeStep.png

So the pressure is not correctly solved. I search for the solver setting for unstructured grid of icoFoam : the "elbow" tutorial. Take that setting gives : have to set DeltaT=1e-7 to avoid

Code:

[12] #0  Foam::error::printStack(Foam::Ostream&) at ??:?
[12] #1  Foam::sigFpe::sigHandler(int) at ??:?
[12] #2  ? in "/usr/lib64/libc.so.6"
[12] #3  Foam::symGaussSeidelSmoother::smooth(Foam::word const&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::Field<double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, unsigned char, int) at ??:?
[12] #4  Foam::symGaussSeidelSmoother::smooth(Foam::Field<double>&, Foam::Field<double> const&, unsigned char, int) const at ??:?
[12] #5  Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
[12] #6  ? at ??:?
[12] #7  ? at ??:?
[12] #8  ? at ??:?
[12] #9  ? at ??:?
[12] #10  ? at ??:?
[12] #11  __libc_start_main in "/usr/lib64/libc.so.6"
[12] #12  ? at ??:?
[newton-t-38:93775] *** Process received signal ***
[newton-t-38:93775] Signal: Floating point exception (8)
[newton-t-38:93775] Signal code:  (-6)
[newton-t-38:93775] Failing at address: 0x64500016e4f
[newton-t-38:93775] [ 0] /usr/lib64/libc.so.6(+0x35670)[0x7faad0986670]
[newton-t-38:93775] [ 1] /usr/lib64/libc.so.6(gsignal+0x37)[0x7faad09865f7]
[newton-t-38:93775] [ 2] /usr/lib64/libc.so.6(+0x35670)[0x7faad0986670]
[newton-t-38:93775] [ 3] /softs/software/OpenFOAM/3.0.0-foss-2016a/OpenFOAM-3.0.0/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so(_ZN4Foam22symGaussSeidelSmoother6smoothERKNS_4wordERNS_5FieldIdEERKNS_9lduMatrixERKS5_RKNS_10FieldFieldIS4_dEERKNS_8UPtrListIKNS_17lduInterfaceFieldEEEhi+0x2e7)[0x7faad19699b7]
[newton-t-38:93775] [ 4] /softs/software/OpenFOAM/3.0.0-foss-2016a/OpenFOAM-3.0.0/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so(_ZNK4Foam22symGaussSeidelSmoother6smoothERNS_5FieldIdEERKS2_hi+0x2a)[0x7faad1969daa]
[newton-t-38:93775] [ 5] /softs/software/OpenFOAM/3.0.0-foss-2016a/OpenFOAM-3.0.0/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so(_ZNK4Foam12smoothSolver5solveERNS_5FieldIdEERKS2_h+0x36b)[0x7faad1962afb]
[newton-t-38:93775] [ 6] icoFoam[0x437307]
[newton-t-38:93775] [ 7] icoFoam[0x45bba2]
[newton-t-38:93775] [ 8] icoFoam[0x45bed5]
[newton-t-38:93775] [ 9] icoFoam[0x45c0cb]
[newton-t-38:93775] [10] icoFoam[0x41e2a5]
[newton-t-38:93775] [11] /usr/lib64/libc.so.6(__libc_start_main+0xf5)[0x7faad0972b15]
[newton-t-38:93775] [12] icoFoam[0x41f0a5]
[newton-t-38:93775] *** End of error message ***

Resulting log for deltaT=1e-7

Code:

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

Create mesh for time = 0


PISO: Operating solver in PISO mode

Reading transportProperties

Reading field p

Reading field U

Reading/calculating face flux field phi


Starting time loop

Time = 1e-07

Courant Number mean: 0 max: 0
smoothSolver:  Solving for Ux, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for Uz, Initial residual = 1, Final residual = 0.00431533, No Iterations 1000
DICPCG:  Solving for p, Initial residual = 1, Final residual = 9.94297e-07, No Iterations 170
DICPCG:  Solving for p, Initial residual = 4.97148e-07, Final residual = 4.97148e-07, No Iterations 0
DICPCG:  Solving for p, Initial residual = 4.97148e-07, Final residual = 4.97148e-07, No Iterations 0
time step continuity errors : sum local = 6.20264e-14, global = 5.75653e-16, cumulative = 5.75653e-16
DICPCG:  Solving for p, Initial residual = 0.00071311, Final residual = 9.95584e-07, No Iterations 119
DICPCG:  Solving for p, Initial residual = 9.96291e-07, Final residual = 9.96291e-07, No Iterations 0
DICPCG:  Solving for p, Initial residual = 9.96291e-07, Final residual = 9.96291e-07, No Iterations 0
time step continuity errors : sum local = 1.24125e-13, global = 2.93483e-15, cumulative = 3.51048e-15
ExecutionTime = 0.95 s  ClockTime = 2 s

Time = 2e-07

Courant Number mean: 3.12606e-08 max: 2.42506e-07
smoothSolver:  Solving for Ux, Initial residual = 0.312894, Final residual = 0.0162492, No Iterations 1000
smoothSolver:  Solving for Uy, Initial residual = 0.312584, Final residual = 0.0157778, No Iterations 1000
smoothSolver:  Solving for Uz, Initial residual = 0.998651, Final residual = 0.000700336, No Iterations 1000
DICPCG:  Solving for p, Initial residual = 1.92216e-05, Final residual = 9.82794e-07, No Iterations 95
DICPCG:  Solving for p, Initial residual = 9.82805e-07, Final residual = 9.82805e-07, No Iterations 0
DICPCG:  Solving for p, Initial residual = 9.82805e-07, Final residual = 9.82805e-07, No Iterations 0
time step continuity errors : sum local = 1.22442e-13, global = 9.4954e-15, cumulative = 1.30059e-14
DICPCG:  Solving for p, Initial residual = 5.43799e-06, Final residual = 9.1311e-07, No Iterations 18
DICPCG:  Solving for p, Initial residual = 9.13111e-07, Final residual = 9.13111e-07, No Iterations 0
DICPCG:  Solving for p, Initial residual = 9.13111e-07, Final residual = 9.13111e-07, No Iterations 0
time step continuity errors : sum local = 1.13759e-13, global = -7.81266e-15, cumulative = 5.19322e-15
ExecutionTime = 2.71 s  ClockTime = 3 s

.........
.........
.........

Time = 2e-06

Courant Number mean: 5.93205e-07 max: 1.04163e-06
smoothSolver:  Solving for Ux, Initial residual = 0.039176, Final residual = 0.0305109, No Iterations 1000
smoothSolver:  Solving for Uy, Initial residual = 0.039092, Final residual = 0.031189, No Iterations 1000
smoothSolver:  Solving for Uz, Initial residual = 0.996365, Final residual = 0.00701699, No Iterations 1000
DICPCG:  Solving for p, Initial residual = 2.24311e-05, Final residual = 9.96784e-07, No Iterations 21
DICPCG:  Solving for p, Initial residual = 9.9677e-07, Final residual = 9.9677e-07, No Iterations 0
DICPCG:  Solving for p, Initial residual = 9.9677e-07, Final residual = 9.9677e-07, No Iterations 0
time step continuity errors : sum local = 1.24186e-13, global = -1.07502e-15, cumulative = -1.70953e-13
DICPCG:  Solving for p, Initial residual = 2.24562e-05, Final residual = 9.90915e-07, No Iterations 21
DICPCG:  Solving for p, Initial residual = 9.90929e-07, Final residual = 9.90929e-07, No Iterations 0
DICPCG:  Solving for p, Initial residual = 9.90929e-07, Final residual = 9.90929e-07, No Iterations 0
time step continuity errors : sum local = 1.23455e-13, global = -5.12061e-15, cumulative = -1.76073e-13
ExecutionTime = 34.06 s  ClockTime = 35 s

So it seems to have problem solving for U but not p (p is now as set : inlet=10, outlet=0 and it looks just fine. Have reached max 5 attachements). Here is the clip for U
U-2e-6.png

kindle · December 2, 2016, 12:45

Settings for elbow
fvSchemes.elbow.txt
fvSolution.elbow.txt

Settings which works with structured grid, found out a little different with cavity though ...
fvSchemes.txt
fvSolution.txt

And I'm using : OpenFOAM/3.0.0-foss-2016a
The mesh I created with Pointwise.

Here is the Tjunction I am working on.
T.png

I tried a structured mesh like butterfly.png as the last one posted without the fillet. But I get div(U) of order 0.1 with my velocity at entry of order 1m/s and the mean area that doesn't satisfy continuity is at the sharp corner (I have two entry [perpendicular between them] and one exit). Without the junction, I get div(U) of order 1.0e-3.

So might be the sharp corner ? To create a fillet the most natural way I can think of is rotating the mesh (type-H just to show the idea) by the white axe. Thus non-structured !

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December 2, 2016, 12:45	For more info	#2
kindle New Member Join Date: Aug 2016 Posts: 16 Blog Entries: 68 Rep Power: 10	Settings for elbow fvSchemes.elbow.txt fvSolution.elbow.txt Settings which works with structured grid, found out a little different with cavity though ... fvSchemes.txt fvSolution.txt And I'm using : OpenFOAM/3.0.0-foss-2016a The mesh I created with Pointwise. Here is the Tjunction I am working on. T.png I tried a structured mesh like butterfly.png as the last one posted without the fillet. But I get div(U) of order 0.1 with my velocity at entry of order 1m/s and the mean area that doesn't satisfy continuity is at the sharp corner (I have two entry [perpendicular between them] and one exit). Without the junction, I get div(U) of order 1.0e-3. So might be the sharp corner ? To create a fillet the most natural way I can think of is rotating the mesh (type-H just to show the idea) by the white axe. Thus non-structured !