Bulk materials like rocks, powders, grains, and fibers are everywhere in the industrial world. However, it is very difficult to predict exactly how these complex materials will flow and behave inside large machines. This is where the Discrete Element Method (DEM) becomes essential. DEM is a powerful numerical method that calculates the exact movement, collisions, and interactions of thousands or millions of individual particles. If you want to see how this mathematical method solves real industrial problems, you can explore our complete library of DEM Simulations tutorial category.
Figure 1: Various industrial applications of Discrete Element Method (DEM) simulations, including drum wear, bed scour, coal combustion, SAG mill wear, and rotary tillers.
To perform these complex calculations, engineers rely on ANSYS Rocky DEM. Rocky is the leading particle simulation software designed to handle bulk material problems with incredible accuracy. It helps engineers simulate realistic particle shapes and predict how they interact with heavy equipment. By using Rocky DEM, you can analyze major problems like material blockages, extreme equipment wear, and high power consumption before you even build the physical machine. Furthermore, it allows you to test different geometries and operating conditions safely and quickly on your computer. In this comprehensive guide, we will explore the complete Rocky workflow, its advanced physics, and its most powerful industrial applications.
Why Rocky? GPU Power & Real Particle Shapes
First, it is important to understand why ANSYS Rocky DEM is different from older software. In the past, traditional Discrete Element Method tools only used perfect spheres to represent materials. However, real materials like crushed rocks, agricultural hay, or pharmaceutical pills are almost never perfect spheres. Therefore, Rocky allows you to use real polyhedral particle shapes. You can easily define custom shapes, such as sphero-cylinders, briquettes, or faceted polyhedrons, to exactly match your physical material. This means that a Rocky DEM simulation gives you much more accurate results when analyzing how materials flow, block, and lock together inside a machine.
Figure 2: Unlike older software, ANSYS Rocky DEM allows engineers to use realistic polyhedral particle shapes, which greatly increases the physical accuracy of the simulation.
Next, calculating the exact collisions of millions of these realistic shapes requires massive computing power. If you only use a standard CPU processor, a complex simulation could take weeks to finish. To solve this problem, Rocky is built with a powerful GPU DEM solver engine. It uses the massive processing power of graphics cards to do the heavy math. Furthermore, it fully supports Multi-GPU processing. This means you can combine several graphic cards together to simulate millions of complex particles in a very short time. Whether you are running a simple transfer chute simulation or a massive model with complex flexible fibers, this true GPU power saves engineers weeks of waiting.
To see a practical example of this combined CPU-GPU processing power in action, you can explore our Powder Conveying DEM Simulation (Screw Conveyor Analysis). In this specific project, we demonstrate how using real particle shapes alongside GPU acceleration makes analyzing a complex screw conveyor incredibly fast and highly accurate.
Figure 3: The screw conveyor DEM-CFD analysis requires the power of both GPU & CPU
The Core Rocky Workflow
Setting up a simulation in ANSYS Rocky DEM is highly logical and user-friendly. The software organizes the setup process vertically in a Data Panel tree, ensuring that engineers do not miss any important details. Step 1 is the Physics Definition. Here, you establish the fundamental rules of your environment by enabling gravity and choosing the correct momentum or rolling resistance models. Following this, Step 2 is Geometries. In this stage, you import your 3D CAD files, such as a conveyor belt, a mixing tank, or a crusher, directly into the software domain.
Once your equipment is imported, you must define how it behaves. Step 3 involves Motion Frames. Rocky allows you to apply highly complex, real-world movements to your equipment, ranging from simple continuous rotations to complex vibrating or pendulum motions. Next, Step 4 requires defining Materials and Interactions. You must assign basic properties like density and stiffness to both the equipment walls and the bulk material. Furthermore, you must define exactly how these materials interact by setting the static friction, dynamic friction, and restitution coefficients for every collision pair.
Figure 4: The standard ANSYS Rocky DEM setup workflow. The Data Panel guides users logically from defining physics and geometries down to particle injection and solver execution.
Finally, you must introduce the bulk material into the system. Step 5 is Particle Definition, where you select the realistic polyhedral shapes and specify the exact size distribution of your material. After the particles are created, Step 6 is defining Inlets and Outlets. You select a surface in your 3D space and tell the software exactly how many tons per hour to inject into the machine. Lastly, Step 7 is the Solver Definition. In this final stage, you define the total simulation time and choose your hardware. By selecting a GPU DEM solver instead of a standard CPU, you can drastically reduce the processing time before hitting the Start button to watch the simulation run.
Particle Definition: Shapes, PSD & Calibration
First, defining the exact physical properties of your particles is a crucial setup step. Since we already know ANSYS Rocky DEM supports real polyhedrons, the software makes it very easy to implement them. You can select built-in default shapes like briquettes, faceted cylinders, or spheres, and adjust their vertical and horizontal aspect ratios. If your material is highly complex, you can simply import a custom 3D STL file. This process ensures that your digital particles structurally match your real physical product, whether it is a pharmaceutical tablet or a jagged rock.
Furthermore, real industrial bulk materials always contain a mixture of different sizes. To represent this accurately, the software uses a Particle Size Distribution (PSD) tool. Instead of choosing one average size for the whole system, engineers can input actual sieve analysis data directly into the setup panel. You simply define the discrete size ranges and enter the cumulative mass percentage for each group. Consequently, Rocky automatically generates a highly realistic, randomized mixture of large and small particles to inject into the simulation domain.
Figure 5: By importing custom 3D shapes and defining an exact Particle Size Distribution (PSD), engineers can digitally recreate the exact physical mixture of their bulk materials.
Finally, after defining the shape and size, the virtual material must be carefully calibrated. Calibration is the essential process of adjusting contact parameters so the digital particles match real-world physics. During this phase, engineers adjust variables such as static friction, dynamic friction, and rolling resistance. To validate these numbers, you run a simple experimental simulation, like the Static Angle of Repose (SAOR) test, and compare the virtual pile angle with physical laboratory results. Once the parameters are perfectly tuned and validated, the digital material is completely ready for massive industrial equipment analysis.
Figure 6: Eight pre-made Rocky projects representing common bench tests
Advanced Physics 1: Particle Breakage & Wear
First, predicting how materials break and how equipment wears down is a major challenge in bulk material handling. Fortunately, ANSYS Rocky DEM allows engineers to accurately simulate these complex physical behaviors without relying on expensive physical tests. The software includes advanced breakage models, such as the Ab-t10 and Tavares models, which calculate the exact fracture of realistic particles during high-stress impacts. Furthermore, Rocky tracks the shear work and impact energy of every single collision. By using proven mathematical models like Archard’s Law, the software predicts how these continuous impacts gradually remove volume and physically modify the 3D surface of the machine walls. Consequently, engineers can visualize the exact wear patterns and lifespan of their equipment before it is ever built.
Figure 7: Rocky DEM accurately simulates particle fragmentation and breakage
To see these heavy-duty applications in action, high-impact environments like grinding mills are excellent examples. These machines experience extreme mechanical stress, and understanding how ore characteristics interact with the mill speed is critical for reducing expensive downtime. If you want to implement this type of physics in your own workflow, you can explore our comprehensive SAG Mill Wear Analysis using Rocky DEM Simulation. In this practical guide, we demonstrate exactly how to set up the Archard wear model, apply realistic particle interactions, and accurately analyze the resulting wear profiles on the internal mill liners.
Figure 8: Visualizing surface wear modification inside a grinding mill using Rocky DEM’s advanced physical models.
Similarly, analyzing continuous flow and abrasion in rotating equipment presents unique engineering challenges. Whether you are dealing with granulation, coating, or mixing, the specific way particles cascade and slide directly determines the structural integrity of your machine walls. Therefore, capturing these sliding friction forces requires careful software calibration. To master this specific analysis, we highly recommend our Rotational Drum Wear: A DEM Simulation with Rocky. This step-by-step resource walks you through the exact process to ensure your virtual wear predictions perfectly match real-world observations, which ultimately helps you optimize your drum design for maximum longevity.
Figure 9: Analyzing continuous flow and abrasive shear wear inside a rotational drum.
Advanced Physics 2: The Flexible Fiber Model
First, simulating flexible materials like hair, crop stalks, or cotton is very difficult in traditional DEM software. However, ANSYS Rocky DEM solves this problem beautifully with its advanced Flexible Fiber model. In this software, a flexible fiber is built by connecting several straight segments, called sphero-cylinders, using virtual joints. When the particles move or hit a machine wall, these joints can stretch, bend, and twist. The software then calculates the exact forces to resist these movements using elastic and viscous damping models. Consequently, engineers can perfectly simulate materials that bend and fold exactly like real-world fibers.
Figure 10: Rocky DEM models flexible fibers by connecting individual segments with virtual joints
Furthermore, this model is highly customizable and is not limited to simple straight lines. You can easily create complex, multi-branched fibers where each branch has a different diameter and stiffness. If your physical material bends permanently and does not return to its original shape, Rocky allows you to use a bilinear elastoplastic model to simulate true plastic deformation. In addition, if the applied force is too strong, you can apply specific failure models to see the fibers actually snap and break. This extreme level of detail is perfect for simulating agricultural machines, like hay harvesters or wood chippers, where crop breakage is essential to the process.
Figure 11: Bilinear elastoplastic model regimes.
Power of Coupling: CFD-DEM (Rocky + Fluent)
First, while ANSYS Rocky is incredibly powerful for simulating solid particles, real-world bulk materials are almost always surrounded by a fluid, such as air or water. To accurately capture how these fluids and solids interact, Rocky DEM seamlessly couples with ANSYS Fluent. This CFD-DEM integration allows engineers to choose between two main methods. In a 1-way coupling, the fluid flow pushes the particles, but the particles do not affect the fluid. However, in dense systems, engineers use 2-way coupling. This means the fluid moves the particles, and the volume and drag of the particles simultaneously push back and change the fluid flow.
Furthermore, 2-way coupling is absolutely essential when designing systems where a massive amount of particles must continuously mix with a gas stream. In large chemical reactors, understanding the exact hydrodynamics of the bed is critical to avoid dead zones and ensure uniform mixing. To see exactly how to set up this complex interaction in the software, you can explore our step-by-step Circulating Fluidized Bed CFD-DEM Analysis. This practical guide shows how mapping fluid forces to particles helps engineers optimize reactor designs for maximum efficiency.
Figure 12: Visualizing the complex interactions between fluid velocity and particle concentration in a circulating fluidized bed
This coupling goes far beyond simple physical movement; it also includes complex thermal and chemical reactions. For example, in the energy production industry, solid fuels are often burned while floating inside a high-velocity gas stream. Tracking the temperature distribution and burning rate of these individual particles is practically impossible to measure in real life. However, you can accurately predict these extreme behaviors by following our Particle Coal Combustion in Fluidized Bed Reactor CFD-DEM Analysis. This demonstrates how coupling Fluent’s chemical reaction models with Rocky’s discrete tracking provides deep insights into emission control and thermal efficiency.
Figure 13: Simulating high-temperature chemical reactions and particle combustion using coupled CFD-DEM solvers.
Finally, CFD-DEM coupling is a major advantage in the agricultural and food processing sectors. In these industries, forced hot air is frequently used to extract water from bulk materials. Therefore, engineers must perfectly balance the hot airflow and the particle movement so the product dries evenly without burning or degrading. ANSYS Rocky DEM includes a powerful built-in Thermal Model to simulate heat transfer within bulk solids. In many industrial systems, particles are heated or cooled as they move through processing equipment. Rocky easily calculates conductive heat transfer, which happens when hot particles touch each other or touch hot machine walls.
We explain this highly sensitive process in our Moisture Removal by Grain Drying System CFD-DEM Rocky Simulation. By utilizing this coupling method, you can precisely optimize your equipment’s drying times while protecting the quality of the final material.
Figure 14: Optimizing airflow and heat transfer to extract moisture from agricultural products without causing thermal damage.
Power of Coupling: FEA (Rocky + Mechanical)
First, designing heavy industrial machinery requires knowing exactly how much physical stress the bulk material applies to the metal structure. Fortunately, ANSYS Rocky offers a direct, seamless coupling feature with ANSYS Mechanical for Finite Element Analysis (FEA). During the DEM simulation, Rocky accurately tracks every individual impact force, shear stress, and continuous pressure load acting on the equipment walls.
Additionally, the software exports these exact dynamic forces directly into the mechanical structural solver without requiring complex manual data conversions. Consequently, engineers can easily predict structural deformation, analyze high-stress weak points, and optimize the metal thickness. Therefore, by using this powerful FEA coupling, companies can prevent very expensive machine failures long before they build the real physical product.
Figure 15: A great example of FEA DEM coupling to study metal deformation
Conclusion
First, mastering ANSYS Rocky DEM opens up incredible opportunities for engineers to solve complex, real-world problems. Throughout this guide, we have explored how Rocky uses massive GPU power to simulate realistic particle shapes instead of just simple spheres. We analyzed how advanced physical models like particle breakage, equipment wear, and flexible fibers can accurately predict material behavior under harsh conditions. By coupling Rocky with ANSYS Fluent and ANSYS Mechanical, you can easily simulate fluid-particle interactions and structural stresses. As a result, these powerful tools help industries design stronger, more efficient machinery while saving significant time and money on physical testing.