Post-processing#

Lethe has built-in post-processing capabilities. All post-processing results are written as VTU, PTVU, and/or PVD files.

The post-processing subsection of the .prm file is according to the following example:

subsection post-processing
 # Enable output of grid, granular temperature, and particles' average velocity
 set lagrangian post-processing = false
 # Enable output of force chains
 set force chains = false
end

Note

By default, post-processing options are set to false to reduce the number of files generated.

Lagrangian post-processing#

The lagrangian post-processing enables VTU files output generated with the same output frequency as the particles’ results (see the Simulation Control section of this guide). The name of the generated files is set by the output name parameter in the simulation_control section plus the suffix -postprocess_data. The files include:

  • The grid of the domain, with the distribution of the subdomains generated by the load balance (more information about load balancing is provided in the Model Parameters section of this guide).

  • The spatial average of the particle’s velocity (in x, y, z and its norm) for each cell.

  • The granular temperature for each cell.

Important

The particles’ average velocity and the granular temperature are cell based results calculated instantaneously at each outputting time-step. This means that they are only instantaneous spatial averages, i.e, DO NOT correspond to temporal averages measured between the outputs. For a higher resolution of the results in time, we recommend the use of a lower output frequency (Simulation Control).

Force chains post-processing#

The force chains feature enables VTU, PTVU, and PVD files to visualize force chains between particles. The name of the generated files is set by the output name parameter in the simulation_control section plus the suffix -force_chains. The files include:

  • Lines to represent normal forces between particles in contact (use wireframe display with paraview).

  • The force value for each line.

Warning

The force chains feature is not implemented for contact occurring through periodic boundaries.

The following video shows force chains for the Rectangular Hopper example.