Mesh movement in OpenFOAM leads to distorted cells

Hi,
it might not be the right forum, as my problem concerns mesh movement in OpenFOAM, but as it is related to FSI computation, maybe someone can help me.
I am trying to simulate a sort of cylinder-flap simulation, with OpenFOAM as fluid solver. At some point my simulation blows up. Looking at the mesh movement, just before the crash the fluid mesh messes up as you can see in the video below:


At the moment of the crash the flap is moving quite fast. The mesh doesn’t follow the movement well, it is like the trailing elements don’t move fast enough. I have always left the “default” configuration in the dynamicMeshDict file: I have tried to change the diffusivity parameter from

diffusivity quadratic inverseDistance (flap);
to
diffusivity inverseFaceDistance (flap);

Hoping that the mesh movement includes further elements, but it is not enough. I haven’t found much information on how to change dinamicMeshDict parameters. If someone can point me to some resources or has some hint it would be great.
Thank you
Claudio

It looks like the cells on the right side get too skewed. I think that OpenFOAM has some way to tune the non-orthogonal correction, but I am not sure if this is what you need here.

On the more FSI-specific side: wouldn’t it maybe make more sense to extend the fine grid region a bit further to the right? This could reduce the skeweness.

@Claudio are there any news regarding this topic? Did you manage to solve your issue? Could we maybe refine the title?

At the moment, the only workaround that I have been able to find is to reduce the timestep, so that the mesh has somehow the time to adapt better, provided that the mesh I posted before wasn’t good: I refined the trailing elements and, to prevent the “collapse” of elements above and below the flap I made them a little coarser…
I have been trying to find different ways to define mesh movement in OpenFOAM, but at the moment I haven’t found a better setup. AFAIK at the moment, diffusivity has no tuning parametets.
Claudio

I guess that OpenFOAM simply needs more sophisticated mesh movement algorithms, based on artificial structural mechanics problems or RBF mapping (https://www.sciencedirect.com/science/article/pii/S0021999116301814).