[asking]

Hi,

I am trying to simulate the flow around and the response of a fixed cylinder interacting at a particular flow rate. Due to the characteristics of my problem, it corresponds to a 2-way FSI problem. I separated the meshing into "transient structural" for the cylinder and the fluid around it into "Fluent".

In this problem, I need a very fine mesh around the cylinder to capture the generation of vortices around it (my goal at the moment is to achieve y+ =1). The problem is that every time I run the simulation I get negative cell volumes. From my understanding, a finer mesh implies a reduction of the time step to avoid the appearance of negative cell volumes. This means a prohibitively small time step to solve my case.

One possible solution that I was thinking of is to create a small fluid zone of a few mm and "glued" it to the cylinder surface. A second zone with a coarser mesh that is more robust in its deformation and an outer water zone. I have no idea how to do this though xd.

The above is just an idea though. I'm open to any suggestion.

TLDR: How to avoid negative cell volume problem with a fine mesh around a cylinder submerged in water?


Thank you

[asking]

I have been trying different configurations and I managed to move the boundary layer fluid zone with the cylinder movement. To do this, I selected the spring smoothing method, selected the coupled surface and then selected "Deform adjacent boundary layer with zone".

The problem I have now is that the rest of the fluid doesn't deform with the movement of the boundary layer fluid zone. I attached some images to show clearly the problem. The mesh density and geometry shown are just for testing rapidly if the mesh deforms or not.

Thanks,