Hi all,
I have a simulation comprising 250k particles of ~100 µm diameter packed loosely between two concentric cylinders. The packing is read from a file with read_data, and I simply want to let the packing settle under gravity for now (gravity is along the axis of the cylinder). I have two mesh walls defining the inner and outer cylinders, and as in the attached images no particles are in contact with the walls.
If I don't import the inner mesh, the particles collapse fine and residual energy and motion damps out quickly. However, with the inner mesh in place I get warnings such as:
INFO: more than 3 touching neighbor mesh elements found, growing contact history
and shortly after this the typical "time step too large or skin too small" warnings from check/timestep/grain appear.
The simulation seems to keep getting "kicks" of energy, and the near-surface particles don't quickly damp down.
I have tried with different mesh element sizes, but to no avail (see attachment). Can anyone explain what the mesh warning above means? Is it related to the mesh itself, or particle-mesh interactions?
Thanks! Mark
| Attachment | Size |
|---|---|
 cylinder_setup.png | 705.56 KB |
| cylinder_setup2.png | 727.95 KB |
| cylinder_setup3.png | 53.83 KB |
| all_meshes.png | 33.32 KB |
msbentley | Thu, 08/02/2012 - 18:44
OK, behaviour was just parameters, but what about the msg?
OK, I think my "unexpected" behaviour was just a poor choice of parameters and setup. But I'd still like to know the meaning of the info message, and if it implies anything for my mesh design.
Thanks, Mark
ckloss | Sun, 08/05/2012 - 14:15
Hi Mark, the info
Hi Mark,
the info message
INFO: more than 3 touching neighbor mesh elements found, growing contact history
means that some particle is touching more than 3 mesh elements at a time. Per default, memory is allocated for 3 element contacts per particle. If more contacts are detected, additional memory for particle-mesh element contact history is allocated (if contact history is used).
So this just informs you about the memory re-allocation. Nothing to worry about. I just put this message so the user can evaluate if the number of particle-element contacts are reasonable (e.g. if the wrong mesh scaling factor was chosen or alike)
Cheers, Christoph