What is Discrete Element Method and how does it work?
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Published on: February 15, 2019
Tasked with developing a robust and scalable process while facing aggressive timelines with limited material, the life of a process development scientist can be hard. A conventional plan is to execute a series of experiments.
However, for a complex multivariate process, this path may take a great deal of time and expensive resources without adding much knowledge or insight. If the process is novel with many unknowns, experimental optimization is even trickier.
So, is there a way to gain increased process insight while sparing expensive material? It turns out there is. Scientists can now use state-of-the-art simulation tools to understand, optimize, and scale their processes.
Rocky DEM provides a unique platform for scientists across the spectrum of powder processing industries to computationally analyze their process by mapping the dynamic interplay of process, material, and geometric variables.
The ever-growing number of successes across a range of industries indicate that Rocky is doing something fundamentally right. It simply models the system as accurately as possible using Discrete Element Method (DEM).
DEM is essentially a first principle physics method that treats each particle of a granular bed individually. Each particle is represented through a representative shape and size that interacts with other particles and equipment geometry.
These interactions are at the heart of the DEM implementation, and they’re captured through different user-specified material properties.
Multiple particle types with different properties (shape and size distribution, density, Young’s Modulus, Poisson’ ratio, adhesion, thermal conductivity, specific energy for breakage, etc.), can be easily specified to capture the unique complexities of the system under investigation.
Rocky DEM can accurately describe each individual particle’s contact behavior using the multiple available literature models, the choice of which is often application based. All the forces acting on a particle are added, and particle acceleration is calculated.
This is then numerically integrated with time to obtain particle velocity and position.
Process scientists can then visualize and predict the temporal and spatial evolution of the granular system.
In order to achieve increased insight, Rocky allows for a number of advanced physical models, including:
Multiphysics Models:Rocky is fully integrated with Ansys and allows state-of-the-art coupling with Computational Fluid Dynamics (CFD), Finite Element Method (FEM) and Lattice Boltzmann (LBM) packages to accurately simulate multiphase multicomponent flows.
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Complex particle shapes: Custom 3D and 2D particles to achieve realistic representation of particles, including high aspect ratio fibers; which can be made rigid or flexible.
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Complex motion: Complicated motion can be easily specified. Free body motion with 6 degrees of freedom can be specified can also be specified within Rocky, so external MultiBody Dynamics (MBD) software is not required.
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Breakage Model: Well established models for particle breakage, like ABT10 and Tavares models are included.
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Energy Spectra: This is a unique statistical model to predict breakage probabilities of granular assembly by accounting for material properties and dynamic collision energetics.
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Wear Model: Wear of 3D geometric surfaces for processing equipment is captured using the Archard’s wear model.
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Thermal model: Conductive and convective heat transfer to capture temperature variation of particle assembly can be easily studied.
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A fully set up DEM model leads to intense calculations, but Rocky’s shared parallel memory technology and unique multi-GPU hardware capacities have proven to be efficient in solving systems containing tens of millions of particles. Problems that could not have been solved before can be done now.
Furthermore, Rocky provides state-of-the-art post-processing tools to help visualize and quantify a wide range of different metrics, including velocity, pressure and stress fields, rates of powder consumption, material breakage, boundary wear, and temperature variation, helping engineers get deep process insight. If required, Rocky’s Python-based API can enable the user to customize the output using scripts and macros.
However, just like solving any other problem, finding answers through simulations also requires engineering insight. It is here that our dedicated, experienced support staff can help you find the solutions you seek by optimizing the available tools.
We offer full support so that you can find fast and accurate answers to your processing problems.
To learn more about the basics of DEM and how it can be applied, download the article below:
Saurabh Sarkar
Applications Engineer, Rocky DEM
Dr. Saurabh Sarkar is an Applications Engineer for the Rocky DEM Business Unit. Prior to joining ESSS, Dr. Sarkar worked as an Adjunct Faculty at Rutgers University and an on-site Consultant at Sunovion Pharmaceuticals where he supported drug formulation and process development activities. He obtained his Ph.D. in Pharmaceutics from the University of Connecticut where his focus was understanding and optimization of different pharmaceutical unit operations using DEM and CFD tools in projects with multiple industrial and government collaborators. He is a Senior Member of the AIChE and serves as an expert reviewer for several journals.
