[Jibran]

Originally Posted by bigphil

Hi Jibran,

I had a look at the presentation on your website, your approach looks very interesting. I would be very interested in seeing more details on your discretisation and solution methodology.
By "mixed", do you mean that your primary variables are displacement/velocity and pressure?

As regards publication of large strain solid dynamics in OpenFOAM, I am not aware of another journal paper but there are a few conference papers, such as:

• http://powerlab.fsb.hr/ped/kturbo/Op...18-06-2007.pdf
• http://congress.cimne.com/eccomas/cf...pers/01178.pdf
• http://sourceforge.net/projects/open...W09_P_0103.pdf
• http://orbit.dtu.dk/files/58571298/T...esentation.pdf

Best regards,
Philip

Dear Philip,

Thank you for providing me with the information and the links.
By mixed I mean that it is a velocity/strains formulation where the primary variables are linear momentum and the deformation gradient tensor.
Hopefully, I will be able to share more details regarding our method in this thread very soon.
Cheers!

[jason]

Hello there,

(forgot to say its the crackStressFoam in extend-bazaar FluidStructureInteraction package)

I'm interested in the crackStressFoam solver (especially for FSI) but I cannot find out anything about it anywhere .. apart from the .C file - Finite volume stress analysis solver for arbitrary crack propagation

Does anybody have any links or tutorials? As it resides in the FluidStructureInteraction directory I'm assuming I can use it for FSI?

Any advice appreciated.

Br

Jason

[will.logie]

Dear Phil,

It would seem that people succeed in validating the hotCylinder case with the FSI thermalStressFoam solver. Your plot here among others.

I've not yet managed to validate thermalStressFoam with the hotCylinder case. Bug fix done.

I have uploaded my case for scrutiny. Any feedback would be greatly appreciated.

Kind regards,
Will.

[will.logie]

The problem I had was one of interpretation.

In the case I uploaded last week the cylinder is not free to deform longitudinally (2-D plane strain), whereas in the case of Timoshenko the cylinder is free to deform longitudinally.

Cheers,
Will.

[MB2]

Hi,
has anyone successfully solved the restart-issue using fsiFoam ?

I tried to restart beamInCrossFlow using foam-extend-3.1 and fsiFoam from extend-bazaar.

It does restart at several different time steps, but looking at the new time steps after restart, one can see a "jump" in the displacement of the fluid-interface and also a "gap" between the fluid-interface and the solid-interface. Also the solution at the end of the run (static situation) is different from the original behaviour (without restart).

Should that work in theory ?
Has anyone similar problems ?

Thanx for help in advance,
Martin

Originally Posted by bigphil

Hi,

In theory it should not be a problem to restart, we just have to make sure all the relevant fields are written out (something seems to want to old cell volumes V0, and also the golbalFaceZone field in parallel).
I will let you know if I get time to look at it.

In short to answer your questions, yep it would be intended to include such functionality.

Philip

[sfmoabdu]

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.

[Jibran]

Dear All,

An article on large strain computational solid dynamics has recently been published in International Journal for Numerical Methods in Engineering.
Please find below a link to the manuscript on researchgate.
https://www.researchgate.net/publica...train_dynamics

Thanks

[bigphil]

Originally Posted by Jibran

Dear All,

An article on large strain computational solid dynamics has recently been published in International Journal for Numerical Methods in Engineering.
Please find below a link to the manuscript on researchgate.
https://www.researchgate.net/publica...train_dynamics

Thanks

Thanks Jibran,

The procedures look very interesting.

Do you intend to share the code?
Was it implemented in OpenFOAM? - from the article - yes

All the best,
Philip

[Jibran]

Originally Posted by bigphil

Thanks Jibran,

The procedures look very interesting.

Do you intend to share the code?
Was it implemented in OpenFOAM? - from the article - yes

All the best,
Philip

Hi Philip,

Thanks for the appreciation.
Yes, you are correct. The methodology has been implemented from scratch in OpenFOAM.

Currently, we are working on the code to extend it to contact mechanics applications.
Once that is achieved we plan to share the code.

[MB2]

Hi Philip,

did you have time to have a look at the restart-issue ?
Would be really nice if it would work..

Martin

Originally Posted by bigphil

Hi,

In theory it should not be a problem to restart, we just have to make sure all the relevant fields are written out (something seems to want to old cell volumes V0, and also the golbalFaceZone field in parallel).
I will let you know if I get time to look at it.

In short to answer your questions, yep it would be intended to include such functionality.

Philip

[May Z]

Originally Posted by bigphil

Hi,

Yep, the new FSI framework (currently located in foam-extend-3.1/extend-bazaar) supersedes the icoFsiElasticNonLinULSolidFoam solver.
Željko presented this framework at the OpenFOAM Workshop 2014 in Zagreb: abstract and slides.

The major improvement with regard to FSI coupling is the implementation of the IQN-ILS algorithm: this seems much better than Aitken's/fixed under-relaxation.
Also, the plugin approach used for the solid and fluid solvers should allow easier extension to other fluid/solid models e.g. multi-phase, compressible, plasticity, etc.

Best,
Philip

Hi, I've been tried fsiFoam in extend-bazaar and used one of the case just changed the geometry. But then I can't see the deformation of the solid part. I don't know why.

[Maimouna]

Originally Posted by May Z

Hi, I've been tried fsiFoam in extend-bazaar and used one of the case just changed the geometry. But then I can't see the deformation of the solid part. I don't know why.

Hi May, I'm using fsiFoam in extend bazaar, could you specify for more clarification please.

Regards,

Maimouna

[May Z]

Originally Posted by Maimouna

Hi May, I'm using fsiFoam in extend bazaar, could you specify for more clarification please.

Regards,

Maimouna

http://pan.baidu.com/s/1nvjc2MX
Hi Maimouna, here's my case, the data of the geometry comes from a benchmark case, but the solid part deforms little.
Thanks,

[heliana60]

Dear Phillip,

I am using the elasticSolidFoam (foam extended 3.1) solver to apply traction to a "simple" system. With simple, I mean geometrically because it is just a plate that's fixed at the bottom and pulled at the top.

This plate though has residual stresses within, so a "body force". I added to the momentum equation this body force that is in the material as an extra term (rho*div(residual stress)). I read in one of the forums for a different case, where the gravity was supposed to be introduced, that you said this force is added only in the first time step, nonetheless I just included directly in the equation (mistake??). It looks like:

fvVectorMatrix UEqn
(
rho*fvm::d2dt2(U)
==
fvm::laplacian(2*muf + lambdaf, U, "laplacian(DU,U)")
+ divSigmaExp + rho*divStress (Body force)
);

What I find so far is that the Young modulus of my system changes when I change the fixedDisplacement (strain on top) when this body force in present. When it is not present it doesn't change. So there is a dependence on the strain (rate).

My first question is if adding the body force like I did in the momentum equation makes sense??
Also I am puzzled with this strain dependence of the elastic modulus because there is no time scale in the momentum equations.

It would be very nice hearing from you,

Kind regards,

Heliana

[bigphil]

Originally Posted by heliana60

Dear Phillip,

I am using the elasticSolidFoam (foam extended 3.1) solver to apply traction to a "simple" system. With simple, I mean geometrically because it is just a plate that's fixed at the bottom and pulled at the top.

This plate though has residual stresses within, so a "body force". I added to the momentum equation this body force that is in the material as an extra term (rho*div(residual stress)). I read in one of the forums for a different case, where the gravity was supposed to be introduced, that you said this force is added only in the first time step, nonetheless I just included directly in the equation (mistake??). It looks like:

fvVectorMatrix UEqn
(
rho*fvm::d2dt2(U)
==
fvm::laplacian(2*muf + lambdaf, U, "laplacian(DU,U)")
+ divSigmaExp + rho*divStress (Body force)
);

What I find so far is that the Young modulus of my system changes when I change the fixedDisplacement (strain on top) when this body force in present. When it is not present it doesn't change. So there is a dependence on the strain (rate).

My first question is if adding the body force like I did in the momentum equation makes sense??
Also I am puzzled with this strain dependence of the elastic modulus because there is no time scale in the momentum equations.

It would be very nice hearing from you,

Kind regards,

Heliana

Hi Heliana,

Is your residual stress a uniform field or do you have some spatially varying data?

To add a residual stress, you would add the divergence of this stress to the momentum equation:

    fvVectorMatrix UEqn
    (
        rho*fvm::d2dt2(U)
  == fvm::laplacian(2*muf + lambdaf, U, "laplacian(DU,U)")
    + divSigmaExp
    + fvc::div(myResidualStressField)
    );

For elasticSolidFoam in fe31, two other changes would be required:
Update the definition of stress in the "elasticSolidFoam/calculateEpsilonSigma.H":

epsilon = symm(gradU);

sigma = 2*mu*epsilon + lambda*(I*tr(epsilon)) + myResidualStressField;

and also for the traction based boundary conditions to be correct (e.g. solidTraction, solidContact, fixedDisplacementZeroShear, ...), you need to modify $FOAM_SRC/solidModels/constitutiveModel/tractionBoundaryGradient/tractionBoundaryGradient.C, add the following code at line 530 (just before plasticity contribution):

        // Add residual stress term to boundary gradient
        if
        (
            patch.boundaryMesh().mesh().foundObject<volSymmTensorField>
            (
                "myResidualStressField"
            )
	)
        {
            const volSymmTensorField& myResStress =
                // patch.boundaryMesh().mesh().foundObject<volSymmTensorField> // typo fix: 4th-Aug-16 
                patch.boundaryMesh().mesh().lookupObject<volSymmTensorField>
                (
                    "myResidualStress"
                );

            gradient -= (n & myResStress);
        }

this assumes that myResidualStress is a volSymmTensorField defined in the solver.

As regards applying the term in just the first time-step, this would only be the case for an incremental solver where the momentum equation is cast in incremental form; for elasticSolidFoam it solves the conservation of total linear momentum so the term should be added every time-step.

For the time dependence, there is a temporal term in the momentum equation 'd2dt2(U)'; this term may be significant for highly transient problems or over a very short time. The implemented constitutive law (Hooke's law) is rate independent. Also, you should check that the solver is converging in each time-step.

Philip

[heliana60]

Hi Philip,

Thank you very much for answering. My field is not uniform across the geometry but varies spatially. I am implementing the changes you suggested, I think I was confused with the other forum about the incremental solver, so now I understand that the "myResidualStressField" should be added every time-step. As soon as it works I let you know!

I struggle in the moment though when compiling the $FOAM_SRC/solidModels/constitutiveModel/tractionBoundaryGradient/tractionBoundaryGradient.C

I get this error:

constitutiveModel/tractionBoundaryGradient/tractionBoundaryGradient.C: In static member function ‘static Foam::tmp<Foam::Field<Foam::Vector<double> > > Foam::tractionBoundaryGradient::snGrad(const vectorField&, const scalarField&, const Foam::word&, const Foam::word&, const Foam::fvPatch&, bool, const Foam::nonLinearGeometry::nonLinearType&, bool)’:
constitutiveModel/tractionBoundaryGradient/tractionBoundaryGradient.C:541:17: error: invalid initialization of reference of type ‘const volSymmTensorField& {aka const Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh>&}’ from expression of type ‘bool’
(

Anyways, I will find a way to work it out I let you know how he solver converges.

Cheers,

Heliana

[bigphil]

Hi Heliana,

For the compilation error, this was my fault, there was a typo in the code I posted:
This line:

patch.boundaryMesh().mesh().foundObject<volSymmTensorField>

should be replaced with this line:

patch.boundaryMesh().mesh().lookupObject<volSymmTensorField>

I have edited the post above to correct this.

Philip

[heliana60]

Hi Philip,

I fixed it like you said and I compiled and runs fine.

This is just a bit of brainstorming:

I was thinking though that at t=0 the only stresses present would be my residual stresses which must then create an initial deformation -- sort of saying it comes inherently within the material -- so I figure I have to initialize or calculate somehow that initial deformation where the calculation must start from at the beginning. I think what I mean is that the initial deformation, when there are residual stresses present cannot be zero but a value that should be calculated with the elasticSolidFoam solver assuming that sigma is zero by myResStressField is not zero, hence I should initialize or calculate this deformation a the beginning right and then start from there right?

Sorry if I put it too complicated

Cheers,

Heliana

[heliana60]

Sorry for the messed message,

After thinking about it I think I can rephrase it better.

Since I have residual stresses in my geometry, I could calculate an initial deformation assuming linear elasticity - Hooke's Law - and this initial deformation would be the initial internal field I would use in U to start my calculation which also includes the residual stresses in the momentum equation.

So I would calculate an initial deformation called DU, hence:

volTensorField gradDU = fvc::grad(DU);
// Hooke's law
myResStress = 2*mu*(symm(gradDU)) + lambda*(I*tr(symm(gradDU)))

I need somehow to calculate DU from the previous equation and then that would be my initial inherent deformation across my geometry (because of those residual stresses), so then it is like my system is initialized with this field and then I use the solver....

Does it make sense at all? or am I just running in circles?

Heliana

[bigphil]

Originally Posted by heliana60

Sorry for the messed message,

After thinking about it I think I can rephrase it better.

Since I have residual stresses in my geometry, I could calculate an initial deformation assuming linear elasticity - Hooke's Law - and this initial deformation would be the initial internal field I would use in U to start my calculation which also includes the residual stresses in the momentum equation.

So I would calculate an initial deformation called DU, hence:

volTensorField gradDU = fvc::grad(DU);
// Hooke's law
myResStress = 2*mu*(symm(gradDU)) + lambda*(I*tr(symm(gradDU)))

I need somehow to calculate DU from the previous equation and then that would be my initial inherent deformation across my geometry (because of those residual stresses), so then it is like my system is initialized with this field and then I use the solver....

Does it make sense at all? or am I just running in circles?

Heliana

Hi Heliana,

Yes, I understand; if the residual stress field is not in equilibrium then it would cause some deformation.

With the suggested modifications, the elasticSolidFoam solver will calculate these deformations in the first time-step. For example, to see this, you could set all your boundary conditions to traction-free (i.e. solidTraction with all zeros) and then run the solver for one time-step; you may need to set one patch to fixedDisplacement to stop the model floating away.
If the residual stress field was not in equilibrium then you will see that the model will deform to reach an equilibrium between the residual stresses and generated internal elastic stresses.

In short, I don't think you need to make any additional changes, the solver already solves for and accounts for this residual deformation.

Philip