Convex particles falling down a chute

In this tutorial we sequentially add packs of convex particles. The particles fall onto a chute, on which the wear is calculated.

Name of the case: Project_Convex_Particles_Chute

Setting up the simulation

As a first step, the particle shape, the used materials command 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 convex:

A single materials command with the name default is used:

The simulation domain ranging from -0.8 to 0.1 in x, from -0.3 to 0.3 in y and from -0.5 to 0.2 in z direction is created:

Meshes and regions

We start by creating a mesh module for calculating the wear on the chute:

This mesh module is used in the following mesh command command for the chute:

Furthermore, an insertion region command is added in this tab:

Physics models

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

Since we added a mesh in the previous section, a wall contact model is also added automatically to this section. We use the same properties of the particle contact model:

Finally, the gravity is enabled:

Per default the gravity has a magnitude of 9.807 and acts into negative z-direction. These defaults can be changed by either setting the magnitude or the direction manually.

Particles

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

	default
Density	2500
k_finnie	1
Young’s modulus	5e6
Poisson’s ratio	0.3
Coefficient of restitution	0.65
Coefficient of friction	0.5

A particle template of shape convex is generated from the file data/cube_small.txt and used to form a particle distribution:

Please note that for a convex particle template you can either specify mass, center of mass and moment of inertia or none of them. If the quantities are not specified, an analytical formula is used for their computation.

A pack of 25 particles with a velocity of 0.1 m/s in the negative z-direction is now inserted every 0.1 seconds. The particles are inserted with random orientation. We use an insertion command command with mode pack:

Simulation control

In this tab, we first define the time-step settings such as the desired simulation timestep of 1e-4 seconds and the total simulation time of 5 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”:

The graphs below show the particle number and the kinetic energy as a function of time:

Also the graph with the cumulated wear can be displayed directly:

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 image below shows the final state of the system, where the particle and the mesh are colored respectively with the velocity and the wear.