Post-processing#
Lethe has built-in post-processing capabilities. All post-processing results are written as VTU, PTVU, PVD, CSV and/or DAT 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
# Enable particle-wall collision statistics
subsection particle wall collision statistics
set enable particle wall contact statistics = false
set collision statistics file = collision_statistics.csv
set verbosity = quiet # Choices are quiet|verbose
set log collisions with all walls = true
set wall boundary ids = 0
end
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.
Particle-wall collision statistics#
The particle-wall contact statistics logging feature allows to log the statistics of collisions between particles and walls in a .dat file or a .csv file. This feature is useful for post-processing and analysis of particle-wall interactions.
enable particle wall collision statistics
enables the feature.collision statistics file
is the name of the file where the particle-wall contact statistics will be logged. The file will be created from the working directory of the simulation. If the name does not specify the format, the file will be created in .csv format. If the name ends with .dat or .csv, the file will be created in the corresponding format.verbosity
controls the verbosity of the particle-wall collisions. The available options arequiet
(the default option) andverbose
. If set toverbose
, the start and the end of a collision are printed in the terminal.log collisions with all walls
is a boolean parameter that controls whether the particle-wall contact statistics will be logged for all walls or only for the walls defined by thewall boundary ids
parameter. If set totrue
, the statistics will be logged for all walls. If set tofalse
, the statistics will be logged only for the walls defined by thewall boundary ids
parameter.wall boundary ids
is the list of the wall boundary IDs where the particle-wall contact statistics will be logged whenlog collisions with all walls
is set to false. Whenlog collisions with all walls
is set to true, this parameter is ignored. Each wall boundary ID must be separated by a comma.