[evxta3]

Hi all, I am modelling a solitary wave impacting a flexible plate with solids4foam. The plate shows a strange beahviour, such as the horizontal displacement is constant over certain times (as in the attached Fig. 1). The force acting on the plate due to the wave is shown in Fig. 2.

It seems that the solid is not updated over those time steps.

Any idea about why this is happening?

Thanks,
Tommaso

[bigphil]

Hi Tommaso,

Can you give more details of your case? For example, the geometry, materials and loading conditions.

Philip

[evxta3]

Hi Philip, thanks for your reply. This was a 2d wave flume with a rectangular plate. The plate material was stainless steel (density: 8000 kg/m^3 and Young's modulus 200 GPa). The plate, partially submerged, was impacted by a solitary wave resulting in the total force shown in the figure in my previous post.

Thanks,
Tommaso

[bigphil]

What are the boundary conditions on the plate?

And what does the log file look like for the time steps where the displacement stays constant?

[evxta3]

The plate is fixed at the bottom

{
type fixedDisplacement;
value uniform (0 0 0);
}

and the remaining boundaries are treated as interface with

{
type solidTraction;
traction uniform ( 0 0 0 );
pressure uniform 0;
value uniform (0 0 0);
}

From the log file it looks like that the plate is not updated at all since the resisuals converged during the time steps where the displacement is constant. Something like that:

PIMPLE: converged in 2 iterations
Setting traction on solid patch
Interpolating from fluid to solid using GGI/AMI interpolation
Total force (fluid) = (-1.30659 -0.787151 -0.926353)
Total force (solid) = (1.30662 0.78712 0.926346)
Evolving solid solver
Solving the momentum equation for D
Corr, res, relRes, matRes, iters
The relative residual has converged
2, 9.99787e-07, 0, 0, 0

If I use a much thicker plate (more cells through the plate thickness) this strange behaviour is not observed anymore.

Thanks,
Tommaso

[bigphil]

For the thinner plate, I suspect that the solid solver prematurely converges in some time steps, which means the displacement stays constant in these steps. You could check if tightening the solution tolerances in constant/solidProperties helps.

[evxta3]

Originally Posted by bigphil

For the thinner plate, I suspect that the solid solver prematurely converges in some time steps, which means the displacement stays constant in these steps. You could check if tightening the solution tolerances in constant/solidProperties helps.

Yes, that helps in some cases (not always though). Thanks Philip!