[skuznet]

Hello!

I'm trying to setup a conjugate heat transfer case. I've solid and fluid domain and have STL surfaces for them.
surfaceCheck says that my STL are OK

surfaceCheck solid.stl
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.x                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.2.x-37940e0cd1ae
Exec   : surfaceCheck solid.stl
Date   : Jun 04 2014
Time   : 11:50:09
Host   : "ubuntu"
PID    : 10414
Case   : /media/ubuntu/run/UCcases/UCsideOptShortNE_run/constant/triSurface
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Reading surface from "solid.stl" ...

Statistics:
Triangles    : 5250
Vertices     : 2475
Bounding Box : (0 -0.00201 -0.000606) (0.002424 0.001414 0.003838)

Region	Size
------	----
solid_to_fluid	4586
minX	154
maxX	154
minY	2
maxY	174
minZ	90
maxZ	90


Surface has no illegal triangles.

Triangle quality (equilateral=1, collapsed=0):
    0 .. 0.05  : 0.219238
    0.05 .. 0.1  : 0.063619
    0.1 .. 0.15  : 0.0548571
    0.15 .. 0.2  : 0.0758095
    0.2 .. 0.25  : 0.104762
    0.25 .. 0.3  : 0.0190476
    0.3 .. 0.35  : 0.0624762
    0.35 .. 0.4  : 0.0647619
    0.4 .. 0.45  : 0.0175238
    0.45 .. 0.5  : 0.0247619
    0.5 .. 0.55  : 0.0613333
    0.55 .. 0.6  : 0.0409524
    0.6 .. 0.65  : 0.0281905
    0.65 .. 0.7  : 0.0148571
    0.7 .. 0.75  : 0.0186667
    0.75 .. 0.8  : 0.0144762
    0.8 .. 0.85  : 0.00152381
    0.85 .. 0.9  : 0.035619
    0.9 .. 0.95  : 0.0373333
    0.95 .. 1  : 0.0401905

    min 3.65063e-05 for triangle 2652
    max 0.997319 for triangle 654

Edges:
    min 5.32471e-05 for edge 1270 points (0.00159507 -0.00101 0.00272163)(0.001616 -0.00101 0.00277059)
    max 0.00506211 for edge 7513 points (0 -0.00201 -0.000606)(0.002424 -0.00201 0.003838)

Checking for points less than 1e-6 of bounding box ((0.002424 0.003424 0.004444) meter) apart.
Found 0 nearby points.

Surface is closed. All edges connected to two faces.

Number of unconnected parts : 1

Number of zones (connected area with consistent normal) : 1


End

snappyHexMesh seems to run OK, but when I run splitMeshRegions -cellZones -overwrite
additionally to solid and fluid domains it creates a number of spurious domains
named domain1, domain2, domain3...
each consisting of few cells.

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.x                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.2.x-37940e0cd1ae
Exec   : splitMeshRegions -cellZones -overwrite
Date   : Jun 04 2014
Time   : 11:35:20
Host   : "ubuntu"
PID    : 10295
Case   : /media/ubuntu/run/UCcases/UCsideOptShortNE_run
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

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

Create mesh for time = 0

Creating single patch per inter-region interface.

Trying to match regions to existing cell zones.


Number of regions:88

Writing region per cell file (for manual decomposition) to "/media/ubuntu/run/UCcases/UCsideOptShortNE_run/constant/cellToRegion"

Writing region per cell as volScalarField to "/media/ubuntu/run/UCcases/UCsideOptShortNE_run/0/cellToRegion"

Region	Cells
------	-----
0	82068
1	306355
2	233478
3	2
4	1
5	1
6	2
7	1
8	2
9	1
10	1
11	17
12	10
13	1
14	8
15	1
16	1
17	3
18	1
19	13
20	8
21	1
22	1
23	1
24	1
25	1
26	1
27	1
28	2
29	2
30	1
31	1
32	1
33	1
34	1
35	1
36	1
37	1
38	2
39	1
40	1
41	1
42	2
43	1
44	1
45	1
46	1
47	1
48	1
49	1
50	1
51	13
52	1
53	8
54	1
55	1
56	2
57	1
58	2
59	1
60	2
61	1
62	1
63	1
64	1
65	1
66	1
67	1
68	2
69	1
70	1
71	1
72	1
73	1
74	1
75	1
76	2
77	2
78	1
79	1
80	2
81	1
82	2
83	1
84	1
85	1
86	1
87	1

Region	Zone	Name
------	----	----
0	-1	domain0
1	1	solid
2	0	fluid
3	-1	domain3
4	-1	domain4
5	-1	domain5
6	-1	domain6
7	-1	domain7
8	-1	domain8
9	-1	domain9
10	-1	domain10
11	-1	domain11
12	-1	domain12
13	-1	domain13
14	-1	domain14
15	-1	domain15
16	-1	domain16
17	-1	domain17
18	-1	domain18
19	-1	domain19
20	-1	domain20
21	-1	domain21
22	-1	domain22
23	-1	domain23
24	-1	domain24
25	-1	domain25
26	-1	domain26
27	-1	domain27
28	-1	domain28
29	-1	domain29
30	-1	domain30
31	-1	domain31
32	-1	domain32
33	-1	domain33
34	-1	domain34
35	-1	domain35
36	-1	domain36
37	-1	domain37
38	-1	domain38
39	-1	domain39
40	-1	domain40
41	-1	domain41
42	-1	domain42
43	-1	domain43
44	-1	domain44
45	-1	domain45
46	-1	domain46
47	-1	domain47
48	-1	domain48
49	-1	domain49
50	-1	domain50
51	-1	domain51
52	-1	domain52
53	-1	domain53
54	-1	domain54
55	-1	domain55
56	-1	domain56
57	-1	domain57
58	-1	domain58
59	-1	domain59
60	-1	domain60
61	-1	domain61
62	-1	domain62
63	-1	domain63
64	-1	domain64
65	-1	domain65
66	-1	domain66
67	-1	domain67
68	-1	domain68
69	-1	domain69
70	-1	domain70
71	-1	domain71
72	-1	domain72
73	-1	domain73
74	-1	domain74
75	-1	domain75
76	-1	domain76
77	-1	domain77
78	-1	domain78
79	-1	domain79
80	-1	domain80
81	-1	domain81
82	-1	domain82
83	-1	domain83
84	-1	domain84
85	-1	domain85
86	-1	domain86
87	-1	domain87

Can anyone please give me an idea what is going wrong with my case and how can i fix it?
Thank you!

[donQi]

Hello Sergey,
me too I am facing exactly the same problem and I have no idea why those extra domains are created.
I just have two clean STL, two regions one fluid, one solid, like you no errors, snappyHexMesh OK, checkMesh OK, yet splitMeshRegion sees 5 regions

Number of regions:5

Region    Cells
------    -----
0    6406
1    7097
2    390
3    5
4    4

Region    Zone    Name
------    ----    ----
0    -1    domain0
1    1    boxAround
2    0    channel
3    -1    domain3
4    -1    domain4

One thing that I noticed is that if I increase in snappyHexMesh the refinement level, splitMeshRegions will create even more unwanted domains:

Region    Cells
------    -----
0    3207344
1    3505266
2    306361
3    1
4    1
5    1
6    1
7    1
8    1
9    1
10    1
11    1
12    1
13    1
14    1
15    1

Region    Zone    Name
------    ----    ----
0    1    boxAround
1    -1    domain1
2    0    channel
3    -1    domain3
4    -1    domain4
5    -1    domain5
6    -1    domain6
7    -1    domain7
8    -1    domain8
9    -1    domain9
10    -1    domain10
11    -1    domain11
12    -1    domain12
13    -1    domain13
14    -1    domain14
15    -1    domain15

[skuznet]

Hi donQi!

I found this discussion
http://www.cfd-online.com/Forums/ope...meshing-3.html
but didn't find solution to my problem.

One possible way to circumvent this issue is to mesh your domains separataly (which of course will the meshes at the boundary inconsisten) and to create a coupled case manually using thouse meshes.

Please let me know if you find the way to fix the problem with extra domains.


Sergey

[Dan N]

Hey you two

I just had the same problem my extra domains cam from voids in my sti file.

so if you hav a hole in your CAD file it will give you an extra domain

Dan.

[skuznet]

Dear Dan,
thank you for your reply. I thought of this, but can't imagine where the void may come from. I created stl in salome by separating surfaces of a solid domain created in a CAD. Initial geometry consisted of a two solid domains and there were no holes between them.

[derekm]

i ve seen it when the cells at the joining between regions are poor match with each other

[skuznet]

Hi Derek!

Can you suggest any cure for this?

[derekm]

It's all about mesh design: making the mesh from one region to the next, one block to the next, have matching cell faces... and making the split along cell boundaries.

Also make sure you delete the file structures created from the phantom regions properly, otherwise you will keep seeing them even when you have fixed the problem.

[smraniaki]

I also have the same problem even with blockMesh. I designed a simple cube using blockMesh with coarse and fine mesh, just to diagnose where the problem is, but I keep seeing extra {domain**} hanging around. I couldn't really find a logical reasoning to at least convince myself where and why this is happening. Let me know if you could come up with a solution.

Best,
Smran

[jiamingliu]

Is this problem solved?

[dasa]

Please verify the regions. You must have missed some volumes in any of the regions.