Velocity fluctuations in pressure loaded case

[armand-sh]

Dear all,

A colleague and I have coupled FEBio with an in-house compressible flow solver (Dirichlet-Neumann weakly coupled). We set up a "2D" case of a Mooney-Rivlin Material with parameters taken from Maas et al. validation paper (https://doi.org/10.1115/1.4005694) and imposed a pressure load at the interface. At atmospheric pressure FEBio computes velocity of the order of 1E-2 < v < 1E-1 m/s or higher. We also ran the same case with an isotropic elastic solid with parameters corresponding to aluminum and observed the same behavior. Moreover, looking at the stress field it looks like we're just solving for noise.
NB : we're solving with timesteps of the order of 1E-10 < dt < 1E-9 since we are restricted by the acoustic CFL in the fluid.

Are those velocities a numerical artifact ? If so how can I set up the case properly ?

Please find the FEBio case enclosed.
If you have any indications feel free to ask me.

Thanks a lot,
Armand.

[ateshian]

Hi Armand,

I am not sure I understand what you are trying to do. The model you attached is an incompressible solid (not a fluid) which is constrained from deforming in all directions except the face on which you apply the pressure. Given your choice of material and boundary conditions, the material would not normally deform and any deformation you observe may be a numerical artifact of not enforcing incompressibility exactly.

It would be helpful if you could clarify how exactly this analysis is related to your in-house compressible flow solver. Are you trying to verify your in-house code against FEBio? Or are you interested in coupling some fluid pressure obtained with your code to apply a boundary condition on a solid being modeled in FEBio?

Best,

Gerard