Explore the intricate dynamics of particle behavior in different industrial applications and their implications for product development.

## The Fundamentals of Particle Behavior

Particle dynamics involves the study of the motion and interactions of discrete, rigid particles within a system. These particles can have various shapes, sizes, and material properties, and their behavior is governed by the principles of classical mechanics, including Newton's laws of motion and the laws of conservation of momentum and energy.

A crucial aspect of particle dynamics is the analysis of particle-particle and particle-boundary interactions. When particles come into contact, they exert forces and torques on each other, leading to phenomena such as collisions, rolling, sliding, and interlocking. These interactions are typically described by contact models that account for normal and tangential forces, friction, and cohesion. Additionally, particles can interact with boundaries or walls within the system, resulting in phenomena like wall friction and particle segregation.

Another important aspect is the consideration of the collective behavior of particle systems. The interactions between individual particles can give rise to emergent bulk properties, such as force chains, shear banding, dilatancy, and the formation of stable or metastable structures. Furthermore, particle dynamics can be influenced by external forces and fields, such as gravity, magnetic or electric fields, or fluid flow, affecting the motion and behavior of particles.

The study of particle dynamics has wide-ranging applications in various industries and fields, including granular material processing, powder technology, pharmaceutical manufacturing, mineral processing, and the modeling of geophysical phenomena like landslides. The image below provides a broader overview of applications, and there are several others where particle dynamics have recently been applied.

## Simulation Technologies

Discrete Element Method (DEM) is a numerical technique for predicting the behavior of bulk solids. Particles are modeled as discrete, rigid bodies that interact with each other and their surroundings through contact forces and torques. The particles can have various shapes, such as spheres, polyhedra, or even arbitrary geometries, and their behavior is governed by Newton's laws of motion and appropriate contact models.

The DEM simulations explicitly resolve the trajectories and rotations of individual particles, accounting for their inertial properties, as well as the interaction forces arising from particle-particle and particle-boundary contacts. These contact forces typically include normal and tangential components, with the latter incorporating frictional effects.

Additionally, cohesive forces, such as van der Waals interactions, can be incorporated to capture the behavior of fine, cohesive powders. The particles can exhibit complex dynamics, including collisions, rolling, sliding, and interlocking, leading to phenomena like force chains, particle segregation, and the emergence of bulk behavior characteristics like shear banding and dilatancy in granular materials.

Ansys Rocky

Ansys Rocky is a cutting-edge discrete element method (DEM) software that specializes in simulating the motion of granular and discontinuous materials. It is recognized as the industry leader for quickly and accurately simulating particle flows, designed to tackle a wide range of engineering problems. Ansys Rocky stands out for its ability to model real particle shapes, including solids, 2D shells, and both rigid and flexible fibers.

The software leverages multi-GPU solver technology, enabling the simulation of various shaped and sized particles across numerous industrial applications. This technology ensures simulations are both fast and accurate, capable of handling scalable, efficient, and large particle counts. Ansys Rocky also includes features for wear modeling, particle breakage, and cohesion, making it a comprehensive tool for particle dynamics simulation.

The capabilities of Ansys Rocky are extensive, allowing users to solve large and complex problems with efficiency. The software supports multi-GPU processing and accurate particle physics. It also offers automation, customization, and CFD coupling (including more Ansys Tools). Additionally, Ansys Rocky provides advanced features such as surface wear analysis, 3D scan import, and non-spherical particle shapes. It includes advanced breakage modeling, multi-body dynamics, and FEA coupling.

With the introduction of new SPH (Smoothed-Particle Hydrodynamics) capabilities and improved GPU algorithms in the 2023 R2 release, Ansys Rocky takes engineering simulations to new heights. These enhancements enable more sophisticated post-processing capabilities, such as streamlines and flow tracers. They also provide improved performance for handling large geometries and multi-GPU cases. In summary, all these capabilities allow virtual experiments and fast/accurate simulations to:

• Increase equipment life and capacity
• Eliminate blockages, and belt and liner punctures
• Reduce power draw, dust, and noise
• Decrease spillage and product degradation
• Enhance mixing; minimize dead zones and segregation
• Evaluate scale-up strategies
• Predict force, torque, and power consumption
• Analyze structural loads by coupling with FEA
• Simulate fluid-granular interactions by coupling with CFD

## Applications

As mentioned before, Ansys Rocky includes different models to better represent contacts, adhesive force effects, rolling resistance, particle breakage, wear, thermal effects and coarse-grain situations. Thus, extensive simulations can be developed using Ansys Rocky, that provides useful information to assess. This offers exciting opportunities for innovation and advancement in various industries. Below are some examples showing industrial applications (Copyrights to Ansys Inc.).

New Engineering Challenges

One of the most promising capabilities of Rocky is the DEM-SPH coupling. The SPH (Smoothed Particle Hydrodynamics) Method is a Lagrangian mesh-free method used to model fluids in fluid-particle simulations. It is particularly useful for problems with high solid content and free surface flows. SPH accounts for the fluid effect on particles and is powered by a computationally efficient GPU-based solver, ensuring full integration into the Rocky UI.

Additionally, the SPH method in Rocky approaches the interaction of fluid and boundaries using a DEM-style interaction. This triangle-based approach is favorable for complex particle shapes, providing more accuracy between fluid elements and boundaries. When powered by a computationally efficient GPU-based solver, the method allows you to solve practical problems quickly in several engineering applications. Find some examples in the following video (Copyright to Ansys Inc.).

The Particle Flow Analysis is reaching new fields of application.

• Bulk Solid Handling
• Sustainability & Green Energy
• Energy, Water and Natural Resource Usage
• Particle Transport including Slurries