I created a large region compared to the radii of particles, and the time-stepping becomes very slow.
region reg block -0.01 8.1 0.0 1.51 -0.01 4.51 units box
The particles radii varies from 0.008 to 0.016, and total # of particles is 10k. So the region is mostly empty.
I tried using shrink-wrapped "boundary s s s" but the issue remains.
Does region mesh/tet help to speed up the simulation?
I tried this feature but failed: the vtk Mesh is closed surface mesh, when importing to Liggghts, it says: VTK mesh file is incompatible with simulation box: One or more vertices outside simulation box, but it shows the same as the original STL mesh in paraview. So what vtk format mesh does "region mesh/tet" need?
Update1: The width in Y has been changed to 0.3m, which becomes a "2D" problem. BUT, the speed of time-stepping remains more or less the same as the large 3D case, how come?