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March 21, 2015, 10:08 
icoFsiElasticNonLinULSolidFoam. eigenvalues problem

#1 
Senior Member
Join Date: Jan 2015
Posts: 132
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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  foamextend: Open Source CFD   \\ / O peration  Version: 3.1   \\ / A nd  Web: http://www.extendproject.de   \\/ M anipulation   \**/ Build : 3.17d8e040bf53d Exec : /opt/foam/foamextend3.1/applications/bin/linux64GccDPOpt/icoFsiElasticNonLinULSolidFoam Date : Mar 21 2015 Time : 15:00:44 Host : sergeyNotebookPC PID : 12838 CtrlDict : /opt/foam/foamextend3.1/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 fluidtosolid and solidtofluid interpolators Check fluidtosolid and solidtofluid interpolators Fluidtosolid face interpolation error: 0.20018 Solidtofluid face interpolation error: 1.11023e16 Starting time loop Time = 0.001 Selecting coupling scheme Aitken Time = 0.001, iteration: 1 Current fsi underrelaxation 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 = 9.87969e12, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.657091, Final residual = 9.85265e12, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 1.05188e11, No Iterations 2 GAMG: Solving for p, Initial residual = 1, Final residual = 4.06804e07, No Iterations 16 GAMG: Solving for p, Initial residual = 0.00154278, Final residual = 4.60129e07, No Iterations 4 time step continuity errors : sum local = 3.54272e07, global = 1.16647e07, cumulative = 1.16647e07 GAMG: Solving for p, Initial residual = 0.000170456, Final residual = 7.44231e07, No Iterations 5 GAMG: Solving for p, Initial residual = 1.77539e05, Final residual = 9.98566e07, No Iterations 1 time step continuity errors : sum local = 7.65403e07, global = 1.52512e07, cumulative = 2.69159e07 Setting traction on solid patch Total traction force = (4.63054e08 2.6171e07 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) 

March 26, 2015, 07:30 

#2 
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Damon Lee
Join Date: Sep 2014
Posts: 16
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Could you post your solid/constant/rheologyProperties and solid/system files? Maybe its
Code:
planeStress no; 

March 26, 2015, 11:46 

#3 
Senior Member
Join Date: Jan 2015
Posts: 132
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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 

May 18, 2015, 08:18 

#4 
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Stephanie
Join Date: Feb 2015
Location: Magdeburg, Germany
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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 

May 21, 2015, 13:09 

#5 
Senior Member
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Yes, I solved this problem. In my case the problem was in incorrect mesh definition, which leads to wrong solidmesh interpolation like:
"Reading coupling properties Create fluidtosolid and solidtofluid interpolators Check fluidtosolid and solidtofluid interpolators Fluidtosolid face interpolation error: 0.20018 Solidtofluid face interpolation error: 1.11023e16Do you also have THIS problem ? 

May 22, 2015, 03:41 

#6 
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Stephanie
Join Date: Feb 2015
Location: Magdeburg, Germany
Posts: 71
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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 fluidtosolid and solidtofluid interpolators Check fluidtosolid and solidtofluid interpolators Fluidtosolid face interpolation error: 1.24127e16 Solidtofluid face interpolation error: 1.24127e16 How did you solved this problem? 

May 22, 2015, 03:49 

#7 
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It's not an error. In my case the patches were not correctly defined so the interpolation error Fluidtosolid 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.


May 22, 2015, 06:56 

#8 
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Stephanie
Join Date: Feb 2015
Location: Magdeburg, Germany
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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 fluidtosolid and solidtofluid interpolators Check fluidtosolid and solidtofluid interpolators Fluidtosolid face interpolation error: 0.167309 Solidtofluid face interpolation error: 0.312902 This was an extract of the log file after I restarted the case. 

May 22, 2015, 09:28 

#9 
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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 ? 

May 22, 2015, 11:19 

#10 
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Stephanie
Join Date: Feb 2015
Location: Magdeburg, Germany
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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. 

June 22, 2015, 11:34 

#11  
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Join Date: Dec 2014
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Quote:
Fluidtosolid face interpolation error: 1e+300 Solidtofluid 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? 

April 2, 2016, 11:34 
interface separation

#12 
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Join Date: Feb 2014
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Dear all
has anyone faced the problem of interface separation? , in which the solid interface moves away from fluid interface (as in the attached snapshot) ... it happens very slowly without any crash of solution and at some time step the gap becomes very big and the solver gives "Floating point exception (core dumped) " or "complex eingenvalues in the matrix ... " !! has anyone of you the solution of that? it happens in both fsiFoam and icoFsiElasticNonLinULSolidfoam. by the way i have used the HronTurek tutorial but i just changed the material and thickness of the plate. Furthermore, the fluid domain is perfectly solved as only CFD. 

September 21, 2016, 10:29 

#13  
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Georg Göbel
Join Date: Sep 2016
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Quote:
i experience the same problem on my cases. I am running a 2Dkind of beamInCrossflow case with a solid density of 4000. First i was using fluid density around 1 and it worked perfectly on a a broad selection of meshes. Then i increased to 4000 an the interfaces seperate. I increased the outer iterations of the interaction and of the deformation solver. Both didn't show any remarkable positive effect. Did you find any solution for the problem? 

Tags 
fluid structure interface, foamextend, fsi simulationns and mesh, openfoamextend 
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