Multibody Dynamics

Rocky DEM allows you the freedom to configure complex geometry movements by enabling many translations, rotation, vibration, swinging, crushing, and free-body motions as you need.

Moreover, Rocky’s fully integrated motion kernel offers support for combined geometry motions right within the software – no need for any third-party motion tools.

So whether you want to prescribe exact movements, or have your geometry components move freely in response to outside forces like particle contacts and gravity, Rocky DEM has your complex motion needs covered.

Possible Movements

• Translation
• Rotation
• Periodic Rotation (Pendulum)
• Periodic Translation (Vibration)
• Free Body Translation
• Free Body Rotation
• Additional Force
• Additional Moment
• Spring-Dashpot Force
• Spring-Dashpot Moment

Create Complex Movements

• Combined Motion
• Nested Frame

Breakage Modeling

Regardless of the particle shape or the application being analyzed, Rocky DEM has the
appropriate breakage model for you. All models can preserve the mass and volume of the original particle.

Instantaneous Fragmentation

The Ab-T10 and the Tavares models allow the representation of hard materials’ brittle breakage, producing randomly shaped fragments with smaller fragments being generated closer to the impact point.

Ab-T10 Breakage Model

Rocky DEM works with both a fracture subdivision algorithm and a breakage energy probability function, which itself is based upon a well-established model in the industry (JKMRC Ab-T10). This breakage model uses arbitrary-shaped convex polyhedrons and can preserve both mass and volume during the breakage process. Also, it treats every particle as a single entity that can be broken into fragments instantaneously based upon the breakage force and/or energy values defined.

Tavares Breakage Model

The Tavares breakage model is an extension of Rocky DEM’s original Ab-T10 breakage model. It has been validated via single-particle testing, and the results have been documented in many peer-reviewed publications over the last 20 years.

This model focuses on fracture by low-energy stressing, which helps in simulating many unit operations in particulate materials processing and handling, where particles are often subject to a complex series of loading events.

Tavares’s breakage model describes the progressive growth of crack-like damage that ultimately leads to the fracture of a particle under stresses significantly lower than those required for breakage in a first event.

Discrete breakage

Rocky’s unique discrete breakage model is a high-fidelity model that considers the collision location at the particle’s surface along with its consequent internal stresses, capturing shape-dependent breakage and crack propagation.
Unlike most DEM codes that use a combination of spheres connected to each other to approximate a particle shape, Rocky uses tetrahedrons, allowing for representation of any particle shape, preserving volume and mass. Thus, it can simulate breakage for particles of any shape and aspect ratio: fibers, shells, and custom shaped particles.

Customization

Rocky DEM’s Application Programming Interface (API) is based on the most-recent technology for customization and user experience integration. This combination provides unique usability, portability and, above all, solver performance. Rocky allows you to customize the application interface, using the Pre & Post API, and to compute advanced custom models using the Solver API.

Pre and Post-API

Scripting API is a great way to save time by automating repeatable tasks. Scripting gives access to Rocky DEM raw data and simulation results, so you can automate your case setup and post-processing steps, especially when you’re performing a complex analysis for many similar kinds of cases. The API can configure and simulate a project from scratch, analyze and export simulation results, and perform computations that go beyond Rocky’s standard feature set.

C++ Solver API

The Solver API is C++ based, and it enables physics such as new contact and joint models, particle properties, body forces, and custom scalars. It gives access to the simulation processing cycle, making it possible to select a specific processing to include a custom code to compute on the solver time. This lets you implement a completely new model to execute on Rocky.
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User Experience

A seamless deployment of custom models, backed by a visual interface in the setup stage, and all new custom variables automatically available for detailed analysis in the post-processing stage.

Single Code For Both Multi-CPU & Multi-GPU Solvers

One single code compatible with both solver technologies, reducing the cost of maintaining custom routines or learning complex GPU programming techniques.

No Performance Degradation

Users can implement custom models using the same structure and logics from embedded models without code virtualization or memory overhead.

Particle and Contact Energy Spectra

Rocky DEM enables you to collect and analyze energy spectra as a useful method to drastically decrease the computational cost of breakage modeling solutions.

This time-saving feature collects the energy statistics of particle collisions to predict breakage and attrition rates for continuous processes and show results in a graphical format, which is helpful in analyzing continuous comminution processes such as grinding mills.

• Particle-based statistics: energy is gathered per particle type (material and size)
• Collision-based statistics: energy is collected per contact type (material, type, and size)

This feature provides insight into how energy is distributed amongst collisions, i.e, in comparing the frequency and power between different colliding pairs.

While missing the high-impact 3D visuals provided by traditional breakage modeling, energy spectra produces actionable results faster by eliminating the computational costs of calculating and visualizing each individual broken fragment..

3D Surface Wear Modification

Rocky DEM can be used as a tool for predicting the abrasive wear of solid surfaces. In addition, Rocky implements a validated Archard’s wear model, providing an accelerated wear model so that months of wear patterns observed in the field can be predicted after a few minutes of virtual simulation.

The transient variation of normal and shear stresses on the surface and their related work are computed accurately and viewed easily.

There are two major ways you can use Rocky to gain an understanding of how your geometries will wear over time:

•  Enabling wear surface modification, which changes the physical appearance of the geometry as the simulation progresses.
• View a color map of the surface intensity.

Collision Statistics

The visualization of collision statistics is a key feature in Rocky DEM.

Intra-particle Collision Statistics

For certain solid and flexible particle sets, you can obtain collision data between two consecutive output time levels. This data can be displayed graphically on the surface of a representative particle, using a conventional field representation with a color scale. You can then differentiate performance for different particle types subject to the same process, or evaluate surface wear and particle chipping.

Inter-particle Collision Statistics

If you want to expand the set of particle properties available for post-processing, including several statistical properties that may be collected during a simulation, you can collect Inter-particle Collision Statistics before processing your simulation. This can be useful when you need to extract data that considers all collisions that happened to a certain particle between two output periods. For example, with impact velocity, you could relate that data to the chances of the particle breaking or causing it to deagglomerate. With duration, you could relate that data to a certain mass or heat transfer process, or to a certain chemical reaction.

Fluid Flow Modeling

Set or Modify Fluid Flow Properties

In Rocky DEM, there are four unique methods for simulating the interaction between particles and the surrounding fluids (air, water, dust, etc.), known more commonly as Computational Fluid Dynamics (CFD).

Lattice Boltzmann Air Flow Method

The first method is accomplished by enabling Rocky to calculate how particle flow and the boundaries that contain those particles affect the air that comes into contact with them.

This method uses the Lattice Boltzmann Method (LBM) for its calculations and is useful for simulating how much dust a transfer chute design would generate, for example.

In this method, the air flow does not affect the movement of the particles; only the particles and the boundaries affect the air flow.

Constant One Way Method

The first of the two One Way methods, the Constant One Way method, is useful in cases where you have a known, unchanging fluid field and want to understand how it impacts the flow of particles without having to use a separate CFD program.

You can set a constant value for density, velocity, viscosity (and thermal properties if thermal is being solved), and Rocky DEM will use those values to simulate the fluid field.

Ansys Fluent One Way Steady State Method

The second of the two One Way methods is accomplished by a one-way steady-state coupling with Ansys Fluent. In this method, a CFD simulation done within Ansys Fluent calculates the velocity and pressure fields generated by the fluid as it flows through the equipment being studied.

At the end of a simulation, or once steady state has reached the flow field, that data is then exported out of Ansys Fluent and imported into Rocky DEM, where Rocky DEM then calculates how the fluid flow would affect the particle flow.

The Ansys Fluent One Way Steady State method is particularly useful for simulating the effect of water on the movement of particles through a pipe, for example. Or, for simulating the transport of particles with different densities by water in a slurry-like flow.

In the Ansys Fluent One Way Steady State method, the particles do not affect the fluid flow; the fluid flow affects the movement of the particles.

Ansys Fluent Two Way Method

The Ansys Fluent Two Way method, is particularly useful for simulating complex phenomena such as pneumatic conveying, granular drying, slurry flow inside grinding mills, or even chemical reactions between particles and fluids.

In the Ansys Fluent Two Way method, the particles are part of the fluid flow and will affect it in a two-way interaction: particles are affected by other particles and the fluid around it while the fluid flow is also affected by the particle pressure.