Particle breakage - Bruchmueller model

In this minimal test case two particles collide with each other, the impact causes a fragmentation of both particles. Initially the particle fragments are all of the same size, and they grow and shrink to their final fragment particle size distribution.

The image shows the two particles before the collision in their original size (upper left). In the next image (upper right) the particles are displayed right after the impact, the fragmentation has taken place but all fragments still are of the same size. In the third image (lower left) the shrinking / growing of the fragments has started but is not completed yet. Finally, in the last image (lower right) the final fragment particle size distribution is reached.

Name of the case: Project_Fragmentation_Bruchmueller

Setting up the simulation

As a first step, the particle shape, the used material and the simulation domain are defined in the General Settings tab. Please note that in case of multiple dependent simulations, the dimensions of the simulation domain can only be defined in the first simulation. This means that the box forming the simulation domain has to be chosen big enough from the beginning.

General settings

In this simulation we set particles of particle shape sphere:

A single materials command with the name default is used:

The simulation domain with x dimensions ranging from -0.11 to 0.11 and y and z dimensions ranging from -0.06 to 0.06 is created:

Meshes and regions

In this simulation neither meshes nor regions are used.

Physics models

The contact models are now defined. For the particles we use the normal contact model hertz/fragmentation/bruchmueller and the tangential model history:

The default gravity command is removed in this section.

Particles

In the general settings tab we only defined a single material type (default), whose settings have to be specified here:

	default
Density	2000
Young’s modulus	5e7
Poisson’s ratio	0.45
Coefficient of restitution	0.6
Coefficient of friction	0.5
breakageE0timesD	0.045
breakageProbabilityParam	1
breakageSizeParam	6

We now add a particle template of style sphere and use it for two create_particle commands:

Simulation control

In this tab, we first define the time-step settings such as the desired simulation timestep of 5e-6 seconds and the total simulation time of 0.04 seconds. Per default also the check_timestep command command is enabled, which throws a warning when the time step exceeds 10 % of the Rayleigh or the Hertz time. These thresholds can be changed by setting an alternative value for hertz_fraction or rayleigh_fraction.

Output settings

In this tab we first define the timestep width for the file and the terminal output:

The output_settings command command the takes care that all particle information and the meshes are written to files accordingly. Furthermore it triggers the output of global quantities such as the kinetic energy of the particles or total normal and shear stresses onto meshes to the terminal. Please note that if the output of per-cell information on meshes such as wear, velocity of stress are desired, one has to add the keyword mesh_properties and select the required output.

Running the simulation

After completing the setup and saving it, the simulation can be launched. Hence, change to the Simulation view. First hit the “Check settings” button, and if the check returns “Check settings successfully completed” the simulation can be run by hitting “Start”.

Postprocessing with Paraview

After the simulation is completed, all data written with the output_settings command can be visualized automatically by going to the Visualization view and hitting the “Start Paraview” button.

The images below show the final state of the settled particles, the coloring is chosen according to the ids: