LIGGGHTS-INL is a capability-extended adaptation of the LIGGGHTS Open Source Discrete Element Method (DEM) Particle Simulation Software based on LIGGGHTS release version 4.0.0.

If you are using results generated with LIGGGHTS-INL, please cite the following articles:

• Yidong Xia, Zhengshou Lai, Tyler Westover, Jordan Klinger, Hai Huang, and Qiushi Chen. "Discrete element modeling of deformable pinewood chips in cyclic loading test." Powder Technology 345 (2019): 1-14. https://doi.org/10.1016/j.powtec.2018.12.072
• Yuan Guo, Qiushi Chen, Yidong Xia, Tyler Westover, Sandra Eksioglu, and Mohammad Roni. "Discrete element modeling of switchgrass particles under compression and rotational shear." Biomass & Bioenergy 141 (2020): 105649. https://doi.org/10.1016/j.biombioe.2020.105649
• Yuan Guo, Qiushi Chen, Yidong Xia, Jordan Klinger, and Vicki Thompson. "A nonlinear elasto-plastic bond model for the discrete element modeling of woody biomass particles." Powder Technology 385 (2021): 557-571. https://doi.org/10.1016/j.powtec.2021.03.008

Users are referred to the LIGGGHTS-PUBLIC documentation (https://www.cfdem.com/media/DEM/docu/Manual.html) for most of the common LIGGGHTS features. Documentation of some of the extended capabilities in LIGGGHTS-INL (e.g., the bonded-sphere model) can be found in this repository. Examples are provided below.

• Documentation of the bonded-sphere model: <repository>/doc/gran_cohesion_bond.html
• User examples of the bonded-sphere model: <repository>/examples/LIGGGHTS/INL/cohesive_bond

• Install OpenMPI: sudo apt-get install libopenmpi-dev openmpi-bin
• Install VTK 7.1: sudo apt-get install libvtk7-dev
• Navigate to <repository>/src/
• Compile the code with VTK: make -j4 mpi_ubuntu-20.04
• If compilation is successful, an executable will be generated: lmp_mpi_ubuntu-20.04

• Use Homebrew to install OpenMPI.
• Install VTK 7.1. Attention: Do not use Homebrew to install VTK. The VTK libraries from Homebrew were pre-built without MPI enabled. So a number of VTK libraries needed by LIGGGHTS-INL are missing, e.g., vtkIOParallel, vtkIOParallel, vtkParallelCore, vtkParallelMPI, and vtkIOParallelXML. We suggest users build VTK 7.1 from source (with MPI enabled and in Release mode) and install the libraries in a common directory. To build VTK from source, additional prerequisite libraries are needed and can be installed from Homebrew.
• Navigate to <repository>/src/
• An example of Makefile for compiling LIGGGHTS-INL on macOS can be found at: <repository>/src/MAKE/Makefile.mpi_vtk-7.1. In this example, we assume that VTK 7.1 is installed in a user-specified diretory: /opt/vtk. So Compile the code with VTK: make -j4 mpi_vtk-7.1.

The following examples of nonlinear contact and bond stiffness models in LIGGGHTS-INL are extended from LIGGGHTS-PUBLIC. No user manual has yet been created for these extended models. Interested users are referred to the listed journal articles and/or user examples below for more information.

An example of controlled collision between two spherical particles can be found at:

<repository>/examples/LIGGGHTS/INL/normal_contact_hysteretic_nonlinear1

The simulation result is shown in the following plot:

An example of macro-fiber made of five bonded spheres can be found at:

<repository>/examples/LIGGGHTS/INL/elastoplastic_bond/chain_bending_mm_2

The simulation result is shown in the following plot:

An example of microfiber made of five bonded spheres can be found at:

<repository>/examples/LIGGGHTS/INL/elastoplastic_bond/chain_bending_um_2

The simulation result is shown in the following plot:

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Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

This software is licensed under the terms you may find in the file named "LICENSE" in this directory.

By contributing to this software project, you are agreeing to the following terms and conditions for your contributions:

You agree your contributions are submitted under the GPL v2 license. You represent you are authorized to make the contributions and grant the license. If your employer has rights to intellectual property that includes your contributions, you represent that you have received permission to make contributions and grant the required license on behalf of that employer.

This is the

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DEM simulation engine, released by DCS Computing GmbH, Linz, Austria www.dcs-computing.com, [email protected]

LIGGGHTS® is open-source, distributed under the terms of the GNU Public License, version 2 or later.

LIGGGHTS® is part of CFDEM®project: www.liggghts.com | www.cfdem.com

Core developer and main author: Christoph Kloss, [email protected]

LIGGGHTS® and CFDEM® are registered trade marks of DCS Computing GmbH, the producer of the LIGGGHTS® software and the CFDEM®coupling software See http://www.cfdem.com/terms-trademark-policy for details.

The LIGGGHTS® distribution includes the following files and directories:

README this file LICENSE the GNU General Public License (GPL) doc documentation examples simple example simulation setups lib libraries LIGGGHTS® can be linked with python Python wrapper on LIGGGHTS® as a library src source files

Point your browser at any of these files to get started:

doc/Manual.html the manual doc/Section_intro.html hi-level introductio doc/Section_start.html how to build and use

Some parts of LIGGGHTS® are based on LAMMPS LAMMPS stands for Large-scale Atomic/Molecular Massively Parallel Simulator.

LAMMPS is Copyright (2003) Sandia Corporation. Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains certain rights in this software. This software is distributed under the GNU General Public License.

LAMMPS is a classical molecular dynamics simulation code designed to run efficiently on parallel computers. It was developed at Sandia National Laboratories, a US Department of Energy facility, with funding from the DOE. It is an open-source code, distributed freely under the terms of the GNU Public License (GPL).

The primary author of LAMMPS is Steve Plimpton, who can be emailed at [email protected]. The LAMMPS WWW Site at lammps.sandia.gov has more information about the code and its uses.

Core developer and main author of LIGGGHTS®: Christoph Kloss, [email protected]