[Thangam]

I am trying to setup a simple fsi problem of a 3d tube (with a small thickness). To achieve this, I started with the 3dTube tutorial and converted it from symmetry to a full 3D problem. I was able to run the "pressure pulse" fsi problem without any issues for this 3D tube.

Now, I want to provide uniform velocity bc at the inlet in order to mimic an artery/flexible tube. However, setting the inlet to

type fixedValue;
value uniform (0 0 1.0);

and pressure at inlet to

 type zeroGradient;

blows up the simulation within the first few iterations. No changes were made to the solid side. The rest of the fvSchemes/fvSolution were kept the same. The error:

Time = 5e-05, iteration: 3
Current fsi under-relaxation factor (wall): 0.05
Maximal accumulated displacement of interface 0: 192.863
GAMG:  Solving for cellMotionUx, Initial residual = 0.999999, Final residual = 0.000243584, No Iterations 1
GAMG:  Solving for cellMotionUy, Initial residual = 0.999996, Final residual = 0.00032079, No Iterations 1
GAMG:  Solving for cellMotionUz, Initial residual = 0.999998, Final residual = 0.000547492, No Iterations 1
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3  Foam::inv(Foam::Field<Foam::SymmTensor<double> >&, Foam::UList<Foam::SymmTensor<double> > const&) at ??:?
#4  Foam::inv(Foam::UList<Foam::SymmTensor<double> > const&) at ??:?
#5  Foam::leastSquaresVectors::calcLeastSquaresVectors() at ??:?
#6  Foam::leastSquaresVectors::movePoints() at ??:?
#7  void Foam::meshObject::movePoints<Foam::fvMesh>(Foam::objectRegistry&) at ??:?
#8  Foam::fvMesh::movePoints(Foam::Field<Foam::Vector<double> > const&) at ??:?
#9  Foam::dynamicMotionSolverFvMesh::update() at ??:?
#10  Foam::fluidSolidInterface::moveFluidMesh() at ??:?
#11  Foam::fluidSolidInterfaces::IQNILSCouplingInterface::evolve() at ??:?
#12  ? in "/nethome/tnatarajan6/OpenFOAM/tnatarajan6-9/platforms/linux64GccDPInt32Opt/bin/solids4Foam"
#13  ? in "/lib/x86_64-linux-gnu/libc.so.6"
#14  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#15  ? in "/nethome/tnatarajan6/OpenFOAM/tnatarajan6-9/platforms/linux64GccDPInt32Opt/bin/solids4Foam"
ERROR

I am using OpenFoam 9.0 and solids4Foam 2.0 on Ubuntu 22.04 as no other combination of OF/solids4Foam/extend work on Ubuntu 22.04.

What should be the approach to run a simple fsi such as a flexible tube with thickness, one inlet and one outlet? I have attached a MWE for the 3D tube that is failing with velocity inlet bc's. Any pointers is appreciated. Thanks.

[ilhado]

Hi Thangam,



Why do you used a velocity of 1.0 m/s in the inlet? Is that only a test?

FSI simulations may be very sensible to the boundary conditions, so what may be the case is that this velocity is too high for the overall physical setup you are using, which would cause large deformations in the solid domain at the initial coupling iterations, thus leading to the divergence (note the huge maximum accumulated displacement in your log). So I would suggested trying with smaller velocities.



That are also other tips for starting an FSI simulation that you can find in this post that may help you: FSI case does not converge, foam extend 4.0


Best,
Iago