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.

Why LIGGGHTS-INL? The public version of LIGGGHTS DEM software, LIGGGHTS-PUBLIC, is maintained by LIGGGHTS community users. LIGGGHTS-INL had been but is no longer a fork of LIGGGHTS-PUBLIC. LIGGGHTS-INL adopts some updates in LIGGGHTS-PUBLIC to fix bugs in the code and offers extended capabilities such as bonded-sphere model (or bonded-particle model in some literature), elastoplastic bond normal stiffness, and strain-hardening nonlinear normal contact model. Those capabilities have been implemented in LIGGGHTS-INL originally for biomass granular flow and structural biomechanics simulations, and can be used for broader applications upon adaptation. For many common scenarios of granular flow simulations that do not require those specialized features, LIGGGHTS-INL can be used interchangeably with LIGGGHTS-PUBLIC, though some input command syntaxes have become different due to our independent maintenance. LIGGGHTS-INL will routinely release user tutorials and examples to improve user experience.

Supported operating systems: Linux and macOS. We provide detailed instructions for installing LIGGGHTS-INL on the Linux Ubuntu LTS and macOS releases.

Reference articles with results generated using LIGGGHTS-INL are listed below:

Static angle of repose

• A. Hamed et al. Flowability of Crumbler rotary shear size-reduced granular biomass: An experiment-informed modeling study on the angle of repose. Frontiers in Energy Research, section Bioenergy and Biofuel (2022). (Open Access)

Uniaxial loading test

• F. Chen et al. A set of hysteretic nonlinear contact models for DEM: Theory, formulation, and application for lignocellulosic biomass. Powder Technology 397 (2022): 117100. (Download Authors' manuscript PDF)
• Y. Xia et al. Discrete element modeling of deformable pinewood chips in cyclic loading test. Powder Technology 345 (2019): 1-14. (Download Authors' manuscript PDF)

Ring shear test

• Y. Guo et al. Discrete element modeling of switchgrass particles under compression and rotational shear. Biomass & Bioenergy 141 (2020): 105649. (Download Authors' manuscript PDF)

Hopper discharge flow

• Z. Lai et al. Discrete element modeling of granular hopper flow of irregular-shaped deformable particles. Advanced Powder Technology 34 (2023): 104106. (Download Authors' manuscript PDF)
• F. Chen et al. Hopper discharge flow dynamics of milled pine and prediction of process upsets using the discrete element method. Powder Technology 415 (2023): 118165. (Download Authors' manuscript PDF)

Screw feeder

• A. Hamed et al. Particle size and shape effect of Crumbler® rotary shear-milled granular woody biomass on the performance of Acrison® screw feeder: A computational and experimental investigation. Powder Technology 427 (2023): 118707. (Open Access)

FEM vs. DEM: granular flow benchmark case studies

• W. Jin et al. On the fidelity of computational models for the flow of milled loblolly pine: A benchmark study on continuum-mechanics models and discrete-particle models. Frontiers in Energy Research, section Bioenergy and Biofuel (2022). (Open Access)

Structural biomechanics

• Q. Sun et al. Reverse scaling of a bonded-sphere DEM model: Formulation and application to lignocellulosic biomass microstructures. Powder Technology 409 (2022): 117797. (Download Authors' manuscript PDF)
• Y. Guo et al. A nonlinear elasto-plastic bond model for the discrete element modeling of woody biomass particles. Powder Technology 385 (2021): 557-571. (Download Authors' manuscript PDF)

We are in the process of releasing tutorials for beginners to use DEM simulation as a numerical tool for granular material flow characterization. Examples can be found here: LIGGGHTS-INL tutorials.

Refer to the LIGGGHTS-PUBLIC documentation for the common LIGGGHTS features. Documentation of some of the LIGGGHTS-INL extended capabilities is in this repository, e.g., the bonded-sphere model (HTML documentation and user examples).

LIGGGHTS-INL provides original nonlinear contact and bond stiffness models. No user manual has yet been created for these models. Refer to the listed articles for more information. User examples are introduced below:

• Strain-hardening nonlinear normal contact: An example of collision between two spherical particles

• Elastoplastic bond normal stiffness (a): An example of macro-fiber made of five bonded spheres

• Elastoplastic bond normal stiffness (b): An example of microfiber made of five bonded spheres

• Micro-biomechanics: An example of compression on a pine wood particle microstructure

• A set of MATLAB codes for 3D image-based porosity analysis: tools/PorosityAnalysis3D
• A concise FIJI user tutorial for 3D image binarization: tools/FIJI

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