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EDEM Contact Models
A Contact Model describes how elements behave when they come into contact with each other.
Rolling Friction Contact Models
Rolling Friction is the resistive force that slows down the motion of a rolling object.
RVD Rolling Friction Model
The RVD Rolling Friction contact model offers an alternative friction calculation to the Standard EDEM Rolling Friction model.

Welcome
About EDEM
EDEM is a high-performance simulation software for bulk and granular materials.
What's New
New features and enhancements available in EDEM.
Release Notes
This section contains information about the EDEM release, such as key features, enhancements, bug fixes, and known issues.
Tutorials
Start using EDEM functionality with our interactive tutorials.
Get Started with EDEM
The EDEM user interface comprises three icons for each simulation component - Creator, Simulator, and Analyst.
EDEM Creator
EDEM Creator is the pre-processor for creating an EDEM simulation model, including setting up equipment and defining the generation of bulk materials.
EDEM Simulator
EDEM Simulator is a powerful solver used for fast and efficient simulations.
EDEM Analyst
EDEM Analyst is the post-processor used to analyze and visualize the results of your simulation.
EDEM Contact Models
A Contact Model describes how elements behave when they come into contact with each other.
- Base Contact Models
  Base Contact models define the physical collision between particle materials or particles and geometries.
- Rolling Friction Contact Models
  Rolling Friction is the resistive force that slows down the motion of a rolling object.
  - Standard Rolling Friction Model
    The Standard Rolling friction contact model is used in simulations where a torque is applied to the contacting surfaces where rolling friction is important.
  - Type C Rolling Friction Model
    The Type C Rolling Friction contact model, proposed by Ai et al. (2011), is an extension of the Standard Rolling Friction model.
  - RVD Rolling Friction Model
    The RVD Rolling Friction contact model offers an alternative friction calculation to the Standard EDEM Rolling Friction model.
- Spinning Friction Contact Model
  The Spinning Friction contact model is used to account for the friction that would occur if a particle face is rotating against another particle or Geometry.
- Additional Contact Models
  You can also add Additional contact models to a simulation.
- Particle Body Force Contact Models
  You can define a particle body force to act on particles when a specified condition is met, when particles are in certain positions, or are traveling at a specified velocity.
- Plug-in Contact Models
  You can add Plug-in contact models to a simulation.
- Field Data Manager
  Field Data Manager allows you to import and manage field data for use in a Custom model (typically, a Particle Body Force).
- Contact Model and GPU Device Compatibility
  The Multi-Sphere solver can run on two different engines such as CPU and CUDA.
EDEM Cal Utility
EDEM Cal is a utility which works with EDEM and is designed to assist in performing calibration.
GPU CUDA Guide
The EDEM CUDA GPU module uses the latest General Purpose Computing on Graphical Processing Units (GPU) technology.
Programming Guide
The EDEM Programming Guide describes the EDEM API.
Coupling Interface Programming Guide
The Coupling Interface Programming Guide provides an overview of how to use the EDEM Coupling Interface to couple with a generic CFD code and/or Multi Body dynamics codes.
EDEMpy
EDEMpy is a Python library for accessing EDEM data from .h5 files (the underlying EDEM file format). EDEMpy does not require prior knowledge of advanced programming.
EDEM Solver Capabilities
EDEM contains four solver engines.
Appendix
This section provides additional information about how to estimate simulation time, supported EDEM File types, attribute definitions, and so on.
EDEM Terminology
Definitions of terms used in EDEM.
References and Bibliography
This section cites the contributions made by various authors and sources that have been used as reference material for EDEM, and the specifics of how they have been applied can be found in the individual contact model sections.

RVD Rolling Friction Model

The RVD Rolling Friction contact model offers an alternative friction calculation to the Standard EDEM Rolling Friction model.

In this model, the rolling friction depends on relative rotational velocity of a pair of elements in contact in a manner suggested in (Zhou, et al. 1999).

This Relative Velocity Dependent (RVD) Rolling Friction model is offered as a 3D generalization of the “Type A: Directional Constant Torque” model type discussed in the paper (Ai, et al. 2011) with one difference in the method of calculating the relative rotational velocity of two elements in contact. While in reference (Ai, et al. 2011) the relative rotational velocity is evaluated from tracking the point of contact, in the EDEM RVD Rolling Friction model, the relative rotational velocity is calculated from the values of instantaneous rotational velocities of two elements in contact as described below. This implementation detail insured proper functionality in three dimensions without affecting the computational time.

In particular, this contact model accounts for rolling friction by applying a constant torque to the contacting surfaces. The torque depends on the relative rotational velocity of two particles in contact, particle i and particle j, as follows:

\begin{array}{l} τ_{i} = - μ_{r} F_{n} R^{*} {\hat{ω}}_{r e l} \\ \vec{τ_{j}} = {\vec{τ}}_{i} \end{array}

With μ_r the coefficient of rolling friction, and R^* is the equivalent radius of two elements in contact. The unit vector of relative rotational velocity, ω_rel, is calculated as follows:

\begin{array}{l} {\hat{ω}}_{r e l} = {\hat{n}}_{i j} \times {\vec{ν}}_{t i j} / |v_{t i j}| \\ {\vec{v}}_{t i j} = \{\begin{array}{l} ^{- \frac{1}{2}} ({\vec{ω}}_{i} + {\vec{ω}}_{j}) \times \vec{r_{i j}}, p a r t i c l e - p a r t i c l e c o n t a c t s \\ - R_{i} \vec{ω_{i}} \times {\hat{n}}_{i j}, p a r t i c l e - g e o m e t r y ​ ​ c o n t a c t s \end{array}\} \end{array}

Where n_ij is a unit vector pointing from particle i to the point of contact as shown in the following figure: