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icoFsiElasticNonLinULSolidFoam. eigenvalues problem

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Old   March 21, 2015, 10:08
Default icoFsiElasticNonLinULSolidFoam. eigenvalues problem
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I'm trying to simulate FSI on simple elastic pipe. I've create both meshes for fluid and solid. checkMesh found no erros. But when I started icoFsiElasticNonLinULSolidFoam I've got a lot of warning about "complex eigenvalues detected for tensor". And after this the program crashes.

The output:
Code:
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | foam-extend: Open Source CFD                    |
|  \\    /   O peration     | Version:     3.1                                |
|   \\  /    A nd           | Web:         http://www.extend-project.de       |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build    : 3.1-7d8e040bf53d
Exec     : /opt/foam/foam-extend-3.1/applications/bin/linux64GccDPOpt/icoFsiElasticNonLinULSolidFoam
Date     : Mar 21 2015
Time     : 15:00:44
Host     : sergey-Notebook-PC
PID      : 12838
CtrlDict : /opt/foam/foam-extend-3.1/etc/controlDict
Case     : /home/sergey/tmp/elastic_pipe/fluid
nProcs   : 1
SigFpe   : Enabling floating point exception trapping (FOAM_SIGFPE).

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

Create dynamic mesh for time = 0

Selecting dynamicFvMesh dynamicMotionSolverFvMesh
Selecting motion solver: laplace
Selecting motion diffusivity: quadratic

Reading transportProperties

Reading field p

Reading field U

Reading/calculating face flux field phi

Reading incremental displacement field DU

Patch vessel    Traction boundary field: DU
        nonLinear set to updated Lagrangian
Reading incremental displacement field DV
Reading accumulated velocity field V

Reading accumulated stress field sigma

Reading incremental stress field DSigma

Selecting rheology model linearElastic
Creating constitutive model

Reading coupling properties
Create fluid-to-solid and solid-to-fluid interpolators
Check fluid-to-solid and solid-to-fluid interpolators
Fluid-to-solid face interpolation error: 0.20018
Solid-to-fluid face interpolation error: 1.11023e-16

Starting time loop

Time = 0.001

Selecting coupling scheme Aitken

Time = 0.001, iteration: 1
Current fsi under-relaxation factor: 0.01
Maximal accumulated displacement of interface points: 0
Courant Number mean: 0 max: 0.765854 velocity magnitude: 0.8
DILUPBiCG:  Solving for Ux, Initial residual = 0.661236, Final residual = 9.87969e-12, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 0.657091, Final residual = 9.85265e-12, No Iterations 2
DILUPBiCG:  Solving for Uz, Initial residual = 1, Final residual = 1.05188e-11, No Iterations 2
GAMG:  Solving for p, Initial residual = 1, Final residual = 4.06804e-07, No Iterations 16
GAMG:  Solving for p, Initial residual = 0.00154278, Final residual = 4.60129e-07, No Iterations 4
time step continuity errors : sum local = 3.54272e-07, global = 1.16647e-07, cumulative = 1.16647e-07
GAMG:  Solving for p, Initial residual = 0.000170456, Final residual = 7.44231e-07, No Iterations 5
GAMG:  Solving for p, Initial residual = 1.77539e-05, Final residual = 9.98566e-07, No Iterations 1
time step continuity errors : sum local = 7.65403e-07, global = 1.52512e-07, cumulative = 2.69159e-07
Setting traction on solid patch
Total traction force = (-4.63054e-08 -2.6171e-07 0.159168)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (-1.15174 0.689561 0.0389201 -0.64029 0.373721 0.0277594 -64.1658 28.6624 -0.601871)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (-1.15174 0.689561 0.0389201 -0.64029 0.373721 0.0277594 -64.1658 28.6624 -0.601871)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (-2.7914 1.59273 0.0193284 -2.34685 2.0507 -0.000694244 -81.644 36.6711 1.82105)
and so on. Any ideas ?
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Old   March 26, 2015, 07:30
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Could you post your solid/constant/rheologyProperties and solid/system files? Maybe its
Code:
 planeStress     no;
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Old   March 26, 2015, 11:46
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Yes, planeStress was no, but when I changes it to "yes" it doesn't help me...
I attach the case files for fluid and solid, maybe it will be useful..

The file size is bigger than 100k, so I upload it to cloud storage: https://yadi.sk/d/wsPFmLZifYBbr
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Old   May 18, 2015, 08:18
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Hey,

did one of you find a solution?
I run the case with one processor and now I have got the same mistake.

I would be verx grateful for anyones help .
best regards,
Stephie
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Old   May 21, 2015, 13:09
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Yes, I solved this problem. In my case the problem was in incorrect mesh definition, which leads to wrong solid-mesh interpolation like:
"Reading coupling properties Create fluid-to-solid and solid-to-fluid interpolators Check fluid-to-solid and solid-to-fluid interpolators Fluid-to-solid face interpolation error: 0.20018 Solid-to-fluid face interpolation error: 1.11023e-16Do you also have THIS problem ?
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Old   May 22, 2015, 03:41
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Hey,
yes I had a look into my log file and there I found the same mistake:

Reading coupling properties
Create fluid-to-solid and solid-to-fluid interpolators
Check fluid-to-solid and solid-to-fluid interpolators
Fluid-to-solid face interpolation error: 1.24127e-16
Solid-to-fluid face interpolation error: 1.24127e-16

How did you solved this problem?
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Old   May 22, 2015, 03:49
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It's not an error. In my case the patches were not correctly defined so the interpolation error Fluid-to-solid face interpolation was very big (0.20018). I simply redefine the patches, so the solid and fluid patches become closer to each other. This fix my problem. But you don't have to solve it, because in your case all is OK with interpolation.
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Old   May 22, 2015, 06:56
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Okay, good news.
Unfortunately, every time I restart the case the interpolation error becommes bigger and bigger.

Reading coupling properties
Reading accumulated fluid interface displacement
Create fluid-to-solid and solid-to-fluid interpolators
Check fluid-to-solid and solid-to-fluid interpolators
Fluid-to-solid face interpolation error: 0.167309
Solid-to-fluid face interpolation error: 0.312902

This was an extract of the log file after I restarted the case.
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Old   May 22, 2015, 09:28
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Very interesting... I can't restart the computation from latestTime. I always have to start my computation from zero time...
How do you find the way to continue simulation from last step ?
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Old   May 22, 2015, 11:19
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If i want to restart the case i change into Fluid and type in icoFsiElasticNonLinULFoam >> log.icoFsiElasticNonLinULFoam
It continues to write the residuals in the log file But be careful it overrides the last log File. So you have to modify the name of the log File. If you run the case in parallel you have to use mpirun. And you have to use startfrom latesttime. I hope i could help you.
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Old   June 22, 2015, 11:34
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Quote:
Originally Posted by Svensen View Post
It's not an error. In my case the patches were not correctly defined so the interpolation error Fluid-to-solid face interpolation was very big (0.20018). I simply redefine the patches, so the solid and fluid patches become closer to each other. This fix my problem. But you don't have to solve it, because in your case all is OK with interpolation.
In my case I got:
Fluid-to-solid face interpolation error: -1e+300
Solid-to-fluid face interpolation error: 0.010357179

I created my mesh with ICEM and the patches actually should be fine because with the exact same geometry my simulation works pretty well with very small interpolation errors.

What can I do to solve this error?
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