# Hollow structure FSI with OpenFOAM and CalculiX

I am trying to simulate the hollow structures with OpenFOAM and CalculiX, such as the implosion of underwater cylindrical shells. The external load of the cylindrical shell is the high hydrostatic pressure, and the internal load is the low ideal air pressure. Can I use the preCICE tools?

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Without knowing much details of your application, I would guess “yes”.
Sounds somehow similar to:

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Through my understanding of preCICE, the fluid-structure coupling calculation of large deformation of shell can indeed be realized. However, because the shell is a hollow structure, the gas inside the shell and the water outside the shell are separated by the structure shell when the fluid-structure interaction calculation is carried out. In the case, the fluid domain is discontinuous and the coupling interface cannot be created. I don’t know how to consider the air inside and water outside the spherical shell at the same time. Could you provide some suggestions about the question?

Hi @JCZheng

An idea to handle the two fluid domains would be to consider them as two different participants from the perspective of coupling. So then you would end up with three participants for the coupling, fluid-gas, fluid-water, and structure-shell. Then you can define two coupling interfaces, fluid-gas – structure-shell and fluid-water – structure-shell. preCICE allows for such a coupling with more than two participants. In our tutorials we have a heat exchanger case which has three participants: tutorials/heat-exchanger at master · precice/tutorials · GitHub. This case is a good starting point to realize such a coupling.

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I have completed the setup of three-phase with twice fluid-solid coupling. However, in order to complete the final implosion simulation, it is best to ensure that the fluid grid is not deformed like the Euler method in the ALE method by moving boundary. Do you have any suggestions?

I don’t fully understand your question. preCICE cannot handle moving meshes, so if the mesh moves in your fluid solver, you can define a second static mesh which remains at the initial position and does not move. Then you can map data between this static mesh and the actual moving mesh in your fluid simulation. Would that be a solution for your problem?

Have you carried out this kind of simulation successfully? I also do research about this problem. Can I communicate with you?

I’m sorry to reply you so late.
As far as I know, only penalty function method or immersion boundary method combined with ghost fluid method can be used to solve the fluid-structure interaction problem (The hollow structure is coupled to internal and external fluid flows). The computational efficiency of the two fluid-structure coupling is too low and does not accord with the physical phenomenon.

Thanks for your reply. I have seen that someone have achieved this physical phenomenon using calculix and openfoam. The link of the paper: Energies | Free Full-Text | A Numerical Study on an Oscillating Water Column Wave Energy Converter with Hyper-Elastic Material (mdpi.com). Thus it can be solved by calculix and openfoam.

Our questions are a little different, but thanks for your reply and supplied paper.

Can we communicate with each other to solve this problem? If you can, please give me your email. Thank you.

Sure！ My email address is zhengjiancaisjtu@163.com

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