# PIC to DEM conversion

The PIC to DEM tool allows to convert a checkpoint file obtained from a PIC run into a new checkpoint file on a custom-refined mesh with DEM particles. The DEM particles positions are initialized such that the original PIC parcels distribution (aka the solids volume fraction) is preserved in each cell up to a negligible error.

Building the PIC to DEM tool using CMake (from inside the build directory):

    cmake --build ./ --target pic2dem

The following inputs must be preceded by “pic2dem.”:

| Description | Type | Default
--- | --- | --- | ---
convert | Name of the checkpoint file obtained from a previous PIC run, that will be converted to a DEM checkpoint file | string | “”
refinement_ratio | The mesh refinement ratio that will be applied on each direction to obtain a refined mesh out of the one read form the PIC checkpoint file | int | 1
eps_tolerance | The threshold used for DEM particles generation from the PIC solids volfrac distribution. If ep_s in a cell is below the threshold, no DEM solids will be generated in that cell | Real | 1.e-15
eps_overflow | An artifact, like a knob, for the user to force over-production (if value > 1), or under-production (if value < 1) of DEM particles | Real | 1.0
small_volfrac | This input gives the possibility to set a small volfrac value just for the DEM refined case, while the standard small volfrac value will still be used for the PIC case read from the checkpoint file | Real |
geom_chk_file | Name of the EB checkpoint file where the DEM refined case geometry will be read or written | string | “”
geom_levelset_chk_file | Name of the EB checkpoint file where the levelset geometry for the DEM refined case will be read or written | string | “”
geom_chk_write | Enable writing the EB geometry checkpoint file for the DEM refined case | bool | false
geom_chk_read | Enable reading the EB geometry checkpoint file for the DEM refined case | bool | false
geometry_filename | CSG filename that will be used for generating the DEM refined geometry in case the PIC coarse geometry is read from a checkpoint file | string | “”