[ARTisticCFD]

I am using fsiFoam with foam-extend 4.0. I am trying to setup an fsi simulation on the same lines as 3dTube example case.
Even if the problem is very similar to the example, it is not going beyond 1st iteration itself.

The relative residuals for solid solver does not go beyond 0.99 and I am not sure why. I ran checkmesh on both of my geometries and all the quality checks are passed.

You could also have a look at my fsiProperties, result log file if needed. I have tried with different values of relaxation factors too, but none of it seem to work.



As far as the solid mesh is concerned, I have generated it from the fluid patch by using extrudeMesh command. I have extruded such that it has only 1 cell in its thickness.



Please help me if you could figure out any mistakes in my settings. Any form of guidance will help me a lot.

[wegner]

Hi, using foam-extend4.0 and fsifoam toolkit, I have encountered the same problem as you. Solving for Dx Dy Dz does not converge and the error appears as " Floating point exception (core dumped)". Besides, the " current fsi under-relaxation factor" is huge.

The mesh should be okay since I followed the exact steps proposed here: http://www.tfd.chalmers.se/~hani/kur...er_reviewd.pdf

Has anyone met (and solved) the problem yet? Some information is listed here.

1. the pointD BC:

boundaryField
{
    RUBLADEsolid
    {
        type            calculated;
        value           uniform (0 0 0);
    }
    RUHUB
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    RUSHROUD
    {
	type            fixedValue;
        value           uniform (0 0 0);
    }
}

2. the D BC:

boundaryField
{
    RUBLADEsolid
    {
        type            tractionDisplacement;
        traction        uniform ( 0 0 0 );
        pressure        uniform 0;
        value           uniform (0 0 0);
    }
    RUHUB
    {
        type            fixedDisplacement;
        value           uniform (0 0 0);
    }
    RUSHROUD
    {
	type            fixedDisplacement;
        value           uniform (0 0 0);
    }   
}

3. the rheologyPropertits (I changed it randomly, and it didn't alter the diverged results):

planeStress no;
rheology
{
    type            linearElastic;
    rho             rho [1 -3 0 0 0 0 0]  100000;
    E               E   [1 -1 -2 0 0 0 0] 5e10;
    nu              nu  [0 0 0 0 0 0 0]   0.4;
}

4. and the error information:

Time = 0.0001, iteration: 1
Current fsi under-relaxation factor: 0.05
Creating accumulated fluid interface displacement
Maximal accumulated displacement of interface points: 0
GAMG:  Solving for cellMotionUx, Initial residual = 0, Final residual = 0, No Iterations 1
GAMG:  Solving for cellMotionUy, Initial residual = 0, Final residual = 0, No Iterations 1
GAMG:  Solving for cellMotionUz, Initial residual = 0, Final residual = 0, No Iterations 1
GAMG:  Solving for cellMotionUx, Initial residual = 0, Final residual = 0, No Iterations 1
GAMG:  Solving for cellMotionUy, Initial residual = 0, Final residual = 0, No Iterations 1
GAMG:  Solving for cellMotionUz, Initial residual = 0, Final residual = 0, No Iterations 1
Evolving fluid solver: consistentIcoFluid
Courant Number mean: 7.12736e-19 max: 0.01 velocity magnitude: 0.5
DILUPBiCG:  Solving for Ux, Initial residual = 1, Final residual = 2.94034e-07, No Iterations 7
DILUPBiCG:  Solving for Uy, Initial residual = 0.999998, Final residual = 3.73936e-07, No Iterations 7
DILUPBiCG:  Solving for Uz, Initial residual = 1, Final residual = 1.39304e-07, No Iterations 8
GAMG:  Solving for p, Initial residual = 1, Final residual = 9.27349e-07, No Iterations 20
GAMG:  Solving for p, Initial residual = 0.0723483, Final residual = 4.49518e-07, No Iterations 14
time step continuity errors : sum local = 5.78997e-09, global = -7.55275e-10
GAMG:  Solving for p, Initial residual = 0.0748816, Final residual = 9.65041e-07, No Iterations 14
GAMG:  Solving for p, Initial residual = 0.0440953, Final residual = 4.29407e-07, No Iterations 12
time step continuity errors : sum local = 4.87308e-09, global = 5.35554e-10
GAMG:  Solving for p, Initial residual = 0.0400866, Final residual = 6.38266e-07, No Iterations 13
GAMG:  Solving for p, Initial residual = 0.024472, Final residual = 4.43531e-07, No Iterations 13
time step continuity errors : sum local = 3.89512e-09, global = 6.78701e-10
Setting traction on solid patch
Total force (fluid) = (-0.0134068 621.105 627.723)
Total force (solid) = (0.0134591 -567.936 -604.765)
Evolving solid solver: unsTotalLagrangianSolid
Creating residual output file
Time: 0.0001, outer iteration: 0
DICPCG:  Solving for Dx, Initial residual = 1, Final residual = 0.0791076, No Iterations 9
DICPCG:  Solving for Dy, Initial residual = 1, Final residual = 0.066415, No Iterations 5
DICPCG:  Solving for Dz, Initial residual = 1, Final residual = 0.0746411, No Iterations 8
Relative residual = 1
Time: 0.0001, outer iteration: 1
DICPCG:  Solving for Dx, Initial residual = 0.999848, Final residual = 0.0609168, No Iterations 4
DICPCG:  Solving for Dy, Initial residual = 0.152375, Final residual = 0.011218, No Iterations 7
DICPCG:  Solving for Dz, Initial residual = 0.142506, Final residual = 0.013695, No Iterations 7
Relative residual = 0.460105
Time: 0.0001, outer iteration: 2
...
...
Time: 0.0001, outer iteration: 198
DICPCG:  Solving for Dx, Initial residual = 0.80369, Final residual = 0.00909372, No Iterations 1
DICPCG:  Solving for Dy, Initial residual = 0.851155, Final residual = 0.00412858, No Iterations 1
DICPCG:  Solving for Dz, Initial residual = 0.82635, Final residual = 0.00559023, No Iterations 1
Relative residual = 1.01305
Time: 0.0001, outer iteration: 199
DICPCG:  Solving for Dx, Initial residual = 0.798573, Final residual = 0.0108907, No Iterations 1
DICPCG:  Solving for Dy, Initial residual = 0.837254, Final residual = 0.00392149, No Iterations 1
DICPCG:  Solving for Dz, Initial residual = 0.810311, Final residual = 0.00622592, No Iterations 1
Relative residual = 1.01913
DICPCG: Solving for D, Initial residula = 1, Final residual = 0.837254, No outer iterations = 200
Max relative residual = 1.19353, Relative residual = 1.01913, enforceLinear = 0
Current fsi relative residual norm: 1
Alternative fsi residual: 1

Time = 0.0001, iteration: 2
Current fsi under-relaxation factor: 0.05
Maximal accumulated displacement of interface points: 2.78575e+142
GAMG:  Solving for cellMotionUx, Initial residual = 1, Final residual = 0.000512934, No Iterations 3
GAMG:  Solving for cellMotionUy, Initial residual = 1, Final residual = 0.000721874, No Iterations 4
GAMG:  Solving for cellMotionUz, Initial residual = 1, Final residual = 0.000722922, No Iterations 3
GAMG:  Solving for cellMotionUx, Initial residual = 0.0429526, Final residual = 2.57213e-05, No Iterations 7
GAMG:  Solving for cellMotionUy, Initial residual = 0.0268615, Final residual = 2.15803e-05, No Iterations 6
GAMG:  Solving for cellMotionUz, Initial residual = 0.0283927, Final residual = 1.53445e-05, No Iterations 6
Floating point exception (core dumped)