Discrete Element Method Calibration with EDEM
Altair EmployeeDiscrete Element Method Calibration with EDEM
Calibration or the use of calibrated models is an important component of any Altair® EDEM™ simulation. This blog summarises the most common discrete element method calibration approach and outlines the resources available.
Why calibrate?
Bulk materials come in all shapes and forms, a material such as coal from one area of the world may behave differently from another part due to local conditions such as moisture content and humidity. In addition the processing of this material may be different resulting in unique size distribution and amounts of fines and therefore different bulk behaviour. For powders one companies processing methodology and additives may be different to another, resulting in unique material bulk behaviour. For accurate numerical modelling of these materials calibration is required against a known experimental measurement.
For more in-depth calibration knowledge please join our regular training sessions or review one of our webinars:
- Register for EDEM training
- Review calibration webinar
- Simple and Efficient Modelling of Powders with the EDEM Powders Database
For more background into EDEM we have a series of e-learning courses:
Calibration methodology
The typical calibration approach is to replicate the conditions of the process we wish to simulate in a small scale lab experiment, then through parameter variation and optimisation obtain our calibrated material model. Key steps are:
- Understand and classify the material
- Understand the process
- Characterize the material with an experimental test
- Reproduce the experimental test and analysis method in EDEM
- Perform parameter optimization to replicate experimental result
Understand and classify the material
The best way to classify a material is to measure its size and size distribution as well as its shape and shape distribution. What do we know about the material already, is this a cohesive or free flowing powder, a series of irregular shaped rocks or a semi-rigid solid block?
Coarse particulate solids can often be modelled at or close to the physical particle size with an approximation of the shape.
Fine particulates typically require a different approach as often it is not practical to model the required number of particles if the requirement is to model the complete system, the material is modelled using larger representative meso-scopic particles.
Understand the process
We need to understand the process to determine if we can model this system directly or reduce the system down to a manageable level. How many particles are in the system and how long do we need to simulate for?
What is happening in the system? Are the particles the dominant physics in the system or do we need to consider adding additional components such as :
- Simulating Fluidized Beds Using CFD-DEM Coupling
- Bulk Material and Multi-body Dynamics Simulation for Heavy Equipment
We also need to know the stress state and flow regime in the system of interest. Is this a semi-static hopper of material under pressure or a material or a dynamic free surface flow in a conveyor transfer system. The stress state is critical in understanding which experimental test to choose.
Characterize the material with an experimental test
Once we understand the process and the material the appropriate test can be chosen. The larger particle types often are in a more free flowing system and the system can be captured with angle of repose and inclined plane tests. Powders maybe dynamic and free flowing or semi-static and under high or low stress in which case the appropriate test needs to be selected.
Calibration tests for Powders
Calibration tests for Soils
Understanding the material and process also allows us to choose from one of the pre-defined already calibrated material models in EDEM:
- Material Models Libraries in EDEM
- Simulating soft soils in EDEM with the Soils Starter Pack
- Simulating powders in EDEM with the Powders Starter Pack (Legacy powders pack)
- Simple and Efficient Modelling of Powders with the EDEM Powders Database (Introduced in EDEM 2022.0)
Reproduce the experimental test and analysis method in EDEM
Finally we are ready to replicate the test, you can choose one of the tests mentioned above or create a custom test for the application.
EDEM has a series of pre-defined tests with automated analysis. For an overview of the tests and kits available see:
The analysis method needs to match the experimental output, this is possible with the default analysis methods in EDEM or can be automated using EDEMpy. The calibration kit includes pre-defined analysis scripts, for more information on EDEMpy see the e-learning:
Perform parameter optimization to replicate experimental result
The common approach is to run simulations of the test multiple times, varying the key interaction parameters each time to match the response of the simulation model to the physical measurement.
HyperStudy is a powerful tool for parameterising and optimising EDEM models:
There are a number of tools to help you get started with this, for example:
- EDEM Tutorials
- How to Calibrate Material Model with EDEM and HyperStudy (YouTube)
- EDEM Batch
- EDEM Physics Models e-learning
- AI-powered Solution to Speed-up System Design and Optimization
If you are looking for further information on EDEM or other Altair products we have plenty more on Altair Community: