What is Rockable?

Rockable is a DEM code written in C++, initiated by vincent.richefeu@3sr-grenoble.fr. The two main specificities of the code are (i) to hold sphero-polyhedral shapes, (ii) to manage breakable interfaces. It is developed for an academic usage. This means that the code is not intended to be a tool for all purposes. It can easily be used to do what it is designed for, but to extend it, it is necessary to master both the model (DEM, complex shapes and interaction laws) and its implementation (data structure). The benefit of a good understanding is to avoid a "hacking" that would eventually limit the developed possibilities. In other words, the design of the code (neither too specific nor too general) is intended to avoid any tendency towards a single thought.

The use of the code is not interfaced by any tool (like lua, python or any graphical interface) to facilitate its use, except the input format as described in the documentation. This makes it particularly streamlined and greatly facilitates its integration with other calculation codes. It is in this sense that Rockable is qualified of "academic code".

Source tree

• sphinxdoc: user documentation (sphinx with ReStructuredText)
• examples: examples for usage tutorials or for testing features
• prepro: some pre-processing tools
• src: C++ source files
• test: regression test files

Folders created at building stage

• deps: source files for Rockable dependencies fetched by cmake
• BUILD: compilation files of the code (created by the script install_rockable.sh)
• INSTALL: binaries of Rockable routines (created by the script install_rockable.sh)

Credits

The code was initially developed by Vincent Richefeu, at Laboratoire 3SR, to model rockfalls and rock avalanches. This has been done through The PhD work of Stiven Cuervo and Bruna Garcia, but it actually started before in a code named DEMbox (no longer maintained).

Then, the breakable interfaces have been implemented during the PhD work of Marta Stasiak. A number of improvements have been added at that time thanks to intensive review with Gael Combe, Laboratoire 3SR.

New functionalities are being studied thanks to new collaborations of people from CEA, IATE and CNRS. For example, Lhassan Amarsid (CEA) is working on the introduction of periodic boundary conditions, and multi-processor computing with domain decomposition. Farhang Radjai and students, may introduce new breakable interfaces with energy-based criteria.

Here is the non-exhaustive list of involved persons with their main mission:

• Vincent Richefeu vincent.richefeu@univ-grenoble-alpes.fr (Laboratoire 3SR, UGA): initiated the project
• Gael Combe gael.combe@univ-grenoble-alpes.fr (Laboratoire 3SR, G-INP): mechanical modelling
• Lhassan Amarsid lhassan.amarsid@cea.fr (CEA): mechanical modelling, parallel computing
• Raphael Prat raphael.prat@cea.fr (CEA): parallel computing
• Jean-Mathieu Vanson jean-mathieu.vanson@cea.fr (CEA): mechanical modelling
• Farhang Radjai franck.radjai@umontpellier.fr (LMGC, CNRS): mechanical/physical Mentor
• Jean-Yves Delenne jean-yves.delenne@inrae.fr (IATE, INRAE): mechanical/biological modelling
• Saeid Nezamabadi saeid.nezamabadi@umontpellier.fr (LMGC, UM2): Non Smooth Discrete Element Method (NS-DEM)
• Patrick Mutabaruka patrick.mutabaruka@ifremer.fr (Ifremer): coupling with Lattice Boltzmann Method (LBM)

Features

• Particle Shapes: the code uses only one 3D shape: sphero-polyhedra or R-shapes. These shapes can be non-convex (with holes if necessary) and have rounded edges and corners (uniform radius per shape).

Note

Some other shapes are currently considered for special boundary shapes (sphere, cylinder...) and specifique loadings.

• Boundary Conditions: any rigid element can be used to apply boundary conditions. It is possible to impose velocity, force, or moment component by component. Some predefined systems with servo-control are also available for complex loading conditions (e.g., loading cycles or controlled pressure).

Note

The possibility of applying tri-periodic loading to an assembly is implemented and currently in the testing phase.

• Parallel Computation: currently, an OpenMP optimization using compilation flags has been implemented. However, the computational speedup is relatively low. Typically, 8 cores are needed to halve the simulation time (for a dense system with a large number of elements).

• Documentation: there is little documentation, although efforts are being made to address this. For now, it is possible to generate the sphinxdoc documentation in your local folder.

How to install

The source code can be cloned from github repository:

git clone https://github.com/richefeu/rockable.git

Using your OS package manager (yum, apt, brew etc) you will maybe need to install several package before compiling: glfw3, opengl,freeglut, libpng2 (optionnal).

If you are lucky, the compilation is as simple as:

sh install_rockable.sh

The compilation is done in the BUILD directory and the binaries go to the INSTALL directory.

Then, if needed, you can manage compilation options (profiling with MATools, full fetch of dependencies, see compilation, prepro compilation etc) using ccmake:

cd BUILD
ccmake .
# Set up options then `c`, then `e`, then `g`
cmake ..
make -j
make install 

The options available are listed below:

• ROCKABLE_USE_FT_CORR (default is OFF): add objectivity correction to tangent forces.
• ROCKABLE_ENABLE_PROFILING (default is OFF): enable time profiling.
• ROCKABLE_ENABLE_BOUNDARY (default is OFF): enable the special boundaries like Ball or Cylinder.
• ROCKABLE_ENABLE_SOFT_PARTICLES (default is OFF): enable straining of particles.
• ROCKABLE_ENABLE_PERIODIC (default is OFF): enable full periodic boundary conditions.
• ROCKABLE_COMPILE_SEE (default is ON): compile the application to visualize the conf-files.
• ROCKABLE_COMPILE_SEE3 (default is OFF): compile the application to edit graphically the input files
• ROCKABLE_COMPILE_CONF2VTK (default is OFF): compile the application to convert .conf into .vtk file to visualize results with paraview
• ROCKABLE_COMPILE_POSTPRO (default is OFF): compile the application for postprocessing the results
• ROCKABLE_COMPILE_PREPRO (default is OFF): compile the aplications to generate inputs for the code

How to run a simulation

Before runing rockable you will need to source rockable environnement to add the INSTALL directory to your standard binaries PATH:

source add_install_to_path.sh

Important

When you run a script, it runs in a subshell, which means any environment variables or changes to the environment, such as adding the INSTALL folder to the PATH, will not persist outside of the script's execution. To make the changes to the PATH persist in your current shell session, you should source the script rather than executing it.

To run a simulation, a configuration file has to be written. The format of such a file is described in the documentation. We show here a simple example (input.txt) simulating a sphere bouncing on a plan.

Rockable 20-02-2017
t 0
tmax 0.06
dt 1e-6
interVerlet 0.01
interConf 0.01

DVerlet 0.08
dVerlet 0.02
density 0 2700
density 1 2700

forceLaw Avalanches
knContact 0 1 1e6
en2Contact 0 1 0.05
ktContact 0 1 1e7
muContact 0 1 0.4
krContact 0 1 1e7
murContact 0 1 0.0

iconf 0
nDriven 1
shapeFile SphereAndPlan.shp
Particles 2
Plan 0 0 1 0 -0.05 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
Sphere 1 0 1 -0.5 0.5 0 3.69 -3.29 0 0 0 0 0.707 0 0.707 0 0 0 -50.52 0 0 0

The shape-file is a file named SphereAndPlan.shp with the following content:

<
name Plan
radius 0.05
preCompDone y
nv 4
2 0 0.5
2 0 -0.5
-2 0 -0.5
-2 0 0.5
ne 4
0 1
1 2
2 3
3 0
nf 1
4 0 1 2 3
obb.extent 2.0 0.05 0.5
obb.e1 1 0 0
obb.e2 0 1 0
obb.e3 0 0 1
obb.center 0 0 0
volume 1
I/m 1 1 1
>

<
name Sphere
radius 0.08
preCompDone y
nv 1
0 0 0
ne 0
nf 0
obb.extent 1 1 1
obb.e1 1 0 0
obb.e2 0 1 0
obb.e3 0 0 1
obb.center 0 0 0
volume 0.004021
I/m 0.00493333 0.00493333 0.0032

Then you can launch Rockable using:

rockable input.txt

If the executable has been compiled with openMP libraries, you can set the number of threads with the option -j:

rockable -j 8 input.txt

The verbosity of logs can be managed:

rockable -v 6 input.txt 

Highest number corresponds highest verbosity. 6: trace, 5: debug, 4: warn, 3: warn, 2: err, 1: critical, 0: off

If the files produced by a computation (conf*, kineticEnergy.txt, perf.txt, and staticBalance.txt) have to be deleted, rockable can do the job.

rockable -c

Visualising the simulations

Normally, the application see has been built at the same time than rockable:

see conf100

If compiled the application see3 is also available:

see3 conf100

It allows to edit confs interactively.