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pimpleDyMfoam , AMI -- The mesh has multiple regions not connected by any face

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Old   September 22, 2015, 05:37
Default pimpleDyMfoam , AMI -- The mesh has multiple regions not connected by any face
  #1
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Sravan Kumar
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Hi All,

I have a problem with pimpleDymFoam.

I trying to simulate pump using pimpleDyMFoam for transient case.

I am timestep as 1e-5 and restricted the maxCo to 1. Also given that timestep is adjustable.
And all other settings similar to propeller tutorial.

Problem is after one or two timesteps the solver is takeing the timestep or 1e-6 and later goes to 1e-7. But runs fine without any errors. But time step ts too small to converge.

I am unable to figure out what the problem is. I have read some posts and they say that some problem with mesh.

I have used the same mesh and boundary conditions for steady state. ( used steady state results for transient case as input. ) It works fine with steady case.

In mesh I have two cellzones one for rotor and other for stator. Is it wrong ??

Is this a problem in AMI ? or Some problem with discretization schemes or solver settings ??

Following is result for checkMesh:

Code:
Create time

Create polyMesh for time = 7000

Time = 7000

Mesh stats
    points:           311575
    faces:            889864
    internal faces:   846488
    cells:            289392
    faces per cell:   6
    boundary patches: 12
    point zones:      0
    face zones:       2
    cell zones:       2

Overall number of cells of each type:
    hexahedra:     289392
    prisms:        0
    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: 2
    The mesh has multiple regions which are not connected by any face.
  <<Writing region information to "7000/cellToRegion"
  <<Writing region 0 with 178544 cells to cellSet region0
  <<Writing region 1 with 110848 cells to cellSet region1

Checking patch topology for multiply connected surfaces...
    Patch               Faces    Points   Surface topology                  
    OUTFLOW             1184     1229     ok (non-closed singly connected)  
    PIPE                3432     3520     ok (non-closed singly connected)  
    CASING              9676     9870     ok (non-closed singly connected)  
    IF2BACKCHANNEL      1208     1359     ok (non-closed singly connected)  
    IF2IMP-AMI1         4228     4379     ok (non-closed singly connected)  
    PASSAGE-HUB         4786     5090     ok (non-closed singly connected)  
    PASSAGE-SHROUD      4786     5090     ok (non-closed singly connected)  
    PASSAGE-OUTFLOW-AMI22688     2856     ok (non-closed singly connected)  
    BLADE               5472     5814     ok (non-closed singly connected)  
    INBLOCK-HUB         2142     2244     ok (non-closed singly connected)  
    INBLOCK-SHROUD      2142     2244     ok (non-closed singly connected)  
    INBLOCK-INFLOW      1632     1734     ok (non-closed singly connected)  

Checking geometry...
    Overall domain bounding box (-0.252091 -0.232021 -0.526682) (1.15 0.274332 0.0749815)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (-5.44028e-17 -2.3469e-17 -9.54647e-17) OK.
    Max cell openness = 1.04888e-15 OK.
    Max aspect ratio = 97.4788 OK.
    Minimum face area = 8.72446e-08. Maximum face area = 0.000588455.  Face area magnitudes OK.
    Min volume = 1.29892e-10. Max volume = 1.56608e-06.  Total volume = 0.0428573.  Cell volumes OK.
    Mesh non-orthogonality Max: 77.509 average: 24.5895
   *Number of severely non-orthogonal (> 70 degrees) faces: 597.
    Non-orthogonality check OK.
  <<Writing 597 non-orthogonal faces to set nonOrthoFaces
    Face pyramids OK.
 ***Max skewness = 4.01477, 2 highly skew faces detected which may impair the quality of the results
  <<Writing 2 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 1 mesh checks
Please help me in this regard. Am new to openFoam and hard to figure out whats going wrong.
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Old   January 20, 2016, 07:14
Default Multiple Mesh connection
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ravi
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Hi. Did you get the answer for the question? I am also facing the same problem. I have 3 meshes and merged all of them. The checkMesh message is as follows:

Please help me.
--------------
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 338216
faces: 3284173
internal faces: 3009863
cells: 1573509
faces per cell: 4
boundary patches: 18
point zones: 0
face zones: 3
cell zones: 3

Overall number of cells of each type:
hexahedra: 0
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 1573509
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: 3
The mesh has multiple regions which are not connected by any face.
<<Writing region information to "0/cellToRegion"
<<Writing region 0 with 408510 cells to cellSet region0
<<Writing region 1 with 936846 cells to cellSet region1
<<Writing region 2 with 228153 cells to cellSet region2

Checking patch topology for multiply connected surfaces...
Patch Faces Points Surface topology
CP_SUCTION 884 539 ok (non-closed singly connected)
INFLOW_SUCTION 907 500 ok (non-closed singly connected)
OUT_INTF_SUCTION 7891 4187 ok (non-closed singly connected)
ROTWALL_SUCTION 11076 6041 ok (non-closed singly connected)
TOP_SUCTION 2609 1486 ok (non-closed singly connected)
BOTTOM_SUCTION 2147 1266 ok (non-closed singly connected)
VANES_SUCTION 19962 10212 ok (non-closed singly connected)
INVOLUTE_SUCTION 13118 6849 ok (non-closed singly connected)
INFLOW_IMPELLER 5700 3044 ok (non-closed singly connected)
OUTFLOW_IMPELLER 4438 2485 ok (non-closed singly connected)
COVERPLATE_IMPELLER 11349 6985 ok (non-closed singly connected)
BACKPLATE_IMPELLER 13893 8628 ok (non-closed singly connected)
BLADE_IMPELLER 150540 77838 ok (non-closed singly connected)
CP_SPIRAL 13102 6656 ok (non-closed singly connected)
OUTFLOW_SPIRAL 398 232 ok (non-closed singly connected)
SP_INFLOW_SPIRAL 7049 3871 ok (non-closed singly connected)
CP_ROTWALL_SPIRAL 5390 2927 ok (non-closed singly connected)
BP_ROTWALL_SPIRAL 3857 2117 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-3.22441 -3.022 -0.132) (1.8 3.22441 1.564)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-1.93389e-17 -4.7934e-18 -6.61003e-18) OK.
Max cell openness = 3.00828e-16 OK.
Max aspect ratio = 18.2351 OK.
Minimum face area = 3.27007e-06. Maximum face area = 0.0345228. Face area magnitudes OK.
Min volume = 3.5911e-09. Max volume = 0.00153684. Total volume = 19.1213. Cell volumes OK.
Mesh non-orthogonality Max: 83.6638 average: 17.3953
*Number of severely non-orthogonal (> 70 degrees) faces: 6.
Non-orthogonality check OK.
<<Writing 6 non-orthogonal faces to set nonOrthoFaces
Face pyramids OK.
Max skewness = 1.12371 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End
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Old   September 21, 2016, 09:03
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Hi to everybody,
I'm facing the same problem in the simulation of a Vertical Axis Wind Turbine with pimpleDyMFoam.
I have imported two different mesh of the windTunnel and the rotating part ( both created in Salome) into an OpenFoam case and merged them with:
mergeMeshes Folder1 Folder2

Now I have a single mesh with two cellZones.
I connected the two overlapping faces of the two meshes using CyclicAMI condition.

However if I run the checkMesh I get:

Code:
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  4.0                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 4.0-665f1db4c1f1
Exec   : checkMesh
Date   : Sep 21 2016
Time   : 14:37:17
Host   : "Delft"
PID    : 8736
Case   : /home/andrea/workspace/FirstPy/src/OpenFOAMTest
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

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

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           141606
    internal points:  0
    faces:            281905
    internal faces:   139658
    cells:            70367
    faces per cell:   5.99092
    boundary patches: 11
    point zones:      0
    face zones:       0
    cell zones:       2

Overall number of cells of each type:
    hexahedra:     69728
    prisms:        639
    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: 2
    The mesh has multiple regions which are not connected by any face.
  <<Writing region information to "0/cellToRegion"
  <<Writing region 0 with 63212 cells to cellSet region0
  <<Writing region 1 with 7155 cells to cellSet region1

Checking patch topology for multiply connected surfaces...
    Patch               Faces    Points   Surface topology                  
    Blade_extruded      146      292      ok (non-closed singly connected)  
    Blade_extruded_rotated146      292      ok (non-closed singly connected)  
    Rotor_Top           63212    63467    ok (non-closed singly connected)  
    Rotor_Bot           63212    63467    ok (non-closed singly connected)  
    PiaWT               7155     7336     ok (non-closed singly connected)  
    Inlet_extruded      20       42       ok (non-closed singly connected)  
    Outlet_extruded     20       42       ok (non-closed singly connected)  
    Sides_extruded      180      364      ok (non-closed singly connected)  
    WC_PiaWT_top        7155     7336     ok (non-closed singly connected)  
    per_int_E           409      818      ok (non-closed singly connected)  
    per_int_I           592      1184     ok (non-closed singly connected)  

Checking geometry...
    Overall domain bounding box (-3 -2 0) (6 2 0.02)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (-5.36979e-20 -2.75947e-20 7.74489e-16) OK.
    Max cell openness = 6.54872e-16 OK.
    Max aspect ratio = 207.23 OK.
    Minimum face area = 8.43604e-08. Maximum face area = 0.0533506.  Face area magnitudes OK.
    Min volume = 1.68721e-09. Max volume = 0.00106701.  Total volume = 0.719986.  Cell volumes OK.
    Mesh non-orthogonality Max: 58.4051 average: 10.9552
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.981359 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End
It tells me that there are two region not connected by any face.
Code:
   *Number of regions: 2
    The mesh has multiple regions which are not connected by any face.
Is it a problem since I'm connecting them with cyclicAMI condition?
Furthermore the simulation, after a while, starts to reduce the timesteps values to contain the Courant number, and then crashes.
The attached image show the situation after few timestep, is correct that the rotating zone and the stationary zone assumes so different values at the interface?
Thanks,
WhiteW
Attached Images
File Type: png image.png (44.2 KB, 20 views)
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ami, centrifugal pump, dynamic mesh, pimpledymfoam

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