[donQi]

Hello,

we have a microwave rocket facility where the intake vanes are deformed after the passage of a shockwave, and we would like to simulate this in openFOAM.

Since we need both FSI and compressibility we were trying to merge icoFsiElasticNonLinULSolidFoam with rhoPisoFoam.

The solver (please find attached) compiles well in foam extend 3.2, but when I test it with the tutorial tutorials/solidMechanics/icoFsiElasticNonLinULSolidFoam/HronTurekFsi/
the following error appears:

Selecting RAS turbulence model laminar
Creating field DpDt
Floating point exception (core dumped)

I think that the floating point exception is originated from DpDT expression in createFields.H
volScalarField DpDt =
fvc:: DDt(surfaceScalarField("phiU", phi/fvc::interpolate(rho)), p);

until now my attempts (like in createFields.H add 0.00001 to avoid 0 division etc) failed.
If anyone has any suggestions will be greatly appreciated.

Best regards,
Al

[donQi]

one more observation : the error above appears using the HronTurekFsi/ left unchanged apart from adding the T file in 0. Turbulence is set off.

[donQi]

the error is due to a division by 0 that happens in createFields.H:

    Info<< "Creating field DpDt\n" << endl;
    
    // debugging
    Info<< "value of p\n" << p << endl;    
    
    volScalarField DpDt =
        // thermo.p();  // for debugging
        fvc::DDt(surfaceScalarField("phiU", phi/fvc::interpolate(rho)), p);

in my p file I was using :

internalField   uniform 0;

boundaryField
{
    plate
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 0;

by setting p to a value different from zero,

internalField   uniform 42;

boundaryField
{
    plate
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 42;

the error disappears and I can go on with further debugging

Creating field DpDt

value of p
dimensions      [1 -1 -2 0 0 0 0];

internalField   uniform 42;

boundaryField
{
    plate
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 42;
    }
    inlet
    {
        type            zeroGradient;
    }
    cylinder
    {
        type            zeroGradient;
    }
    bottom
    {
        type            zeroGradient;
    }
    top
    {
        type            zeroGradient;
    }
    frontAndBackPlanes
    {
        type            empty;
    }
}

Reading incremental displacement field DU

Patch plate    Traction boundary field: DU
    nonLinear set to updated Lagrangian
--> FOAM Warning : The gradScheme for DU should be "extendedLeastSquares 0" for the boundary non-orthogonal correction to be right
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: 1.24127e-16
Solid-to-fluid face interpolation error: 1.24127e-16
Courant Number mean: 0 max: 0 velocity magnitude: 0

Starting time loop

Time = 0.001

Courant Number mean: 0 max: 0 velocity magnitude: 0
Selecting coupling scheme Aitken

[donQi]

I attach here the current version of the solver. It runs without errors with a slightly modified version of the HronTurekFsi tutorial, but handle with care, still needs validation.

[donQi]

I attach also the modified version of HronTurekFsi used as test case for the solver.
for size reason the fluid.msh is not included, you can copy it from the original HronTurekFsi tutorial

[Mehdi3031]

based on my experience this error can be due to two reasons:
1) you made mistake in changing and modifying the solver
2) in your initialization, one of the fields lets say P , is given as

internalField   uniform 0;

which is being used in your solver in denominator and causes a division by zero! so try to give a non zero value to all the internal fields like 0.001, any how its a first guess and will be updated and wont change anything in the final result.

Hope it will help
Mehdi