PLAPIQUI uses Rocky DEM to study particulate systems for the food industry

Rocky DEM is a powerful tool for the chemical engineering research center to calibrate parameters of corn kernels

The Chemical Engineering Pilot Plant (PLAPIQUI) is now using Rocky DEM in simulations and modeling of particulate systems. PLAPIQUI is a center for research, education, and technological development maintained by the National University of South (UNS) and the National Council of Scientific and Technical Research (CONICET), both based in Argentina.

Since 2018, Rocky DEM has performed simulations in PLAPIQUI’S Particle Technology area, mainly in the food and pharmaceutical industries. The following is a case study showing how Rocky DEM  calibrated the parameters of corn kernels.

Rocky DEM calibrates and determines the parameters of corn kernels

This PLAPIQUI project examining the parameters of corn kernels was developed by a Chemical Engineering student at UNS, Manuela Lucia Quezada Henry, guided by the professors Ivana Cotabarren and Juliana Piña.

Traditional calculation methods can’t analyze particulate solids phenomena, which are often needed in many industries. That’s why Discrete Elements Method (DEM) plays a key role in solving this type of problem. In this study, the properties of the corn kernels were determined experimentally (the angle of rest and restitution coefficient), and the rolling resistance coefficient was calibrated via Rocky DEM software (ESSS), modeling the particles in two different ways: as spheres and polyhedra.

“We tested angles of rest, restitution coefficients and complete particle characterization by image analysis. We simulated the experimental angle-of-rest system to calibrate the ‘rolling coefficient’ by comparing real particles to spheres and polyhedra, which allowed us to reach the best approximations for the latter,”said Ivana Cotabarren.

To obtain the rolling resistance coefficient of corn particles, Rocky DEM numerically implemented the angle of rest. . The configuration and the experimental procedure were replicated as closely to reality as possible. The parameter value was modified iteratively until the angle of rest obtained in the simulation coincided with the experimental value. Figure 1 shows the simulated system in the program.

Figure 1: Image of the simulated system in Rocky DEM
Figure 1: Image of the simulated system in Rocky DEM.

Results from Rocky DEM in the calibration of corn kernel parameters

According to Professor Cotabarren, the results indicate that Rocky DEM’s ability to simulate irregular particles leads to better results than the ones obtained by other Discrete Elements Method (DEM) software , in which representation is based only on spherical particles.

In fact, it was only possible to reach the experimentally measured angle of rest values by considering the polyhedral representation of corn kernels.

Among the main implications observed in the study, the simulation time variation needed for polyhedral and spherical particles stands out. Depending on the rolling resistance coefficient, the simulation time tends to increase. For polyhedral particles, it was 20 times longer than that required for the spherical ones, although it was not possible to reproduce the experimental values ​​of the rest angle with the latter. The table below shows the simulation times required for polyhedral particles.

Table: Simulation times and simulated times for polyhedral particles.Table: Simulation times and simulated times for polyhedral particles.

Researchers observed that, in prior simulations with the polyhedral particles, the simulated experience time needed to be extended, since the particles continued to move for several seconds after the fall, changing the shape of the corn pile and, consequently, the angle of rest. This is related to the rolling resistance coefficient presented by the particles.

In Figures 2 and 3, notice the stack formed in the polyhedral-particle simulation with a rolling resistance coefficient of 0.25 at different instants. The shape of the stack changes noticeably after a few seconds. That is why the simulated time was increased in a way that the particles would’ve stopped moving at the end of the simulation.

Figure 2: Stack of particles at 7.5s (a) and 10s (b).

Figure 2: Stack of particles at 7.5s (a) and 10s (b).

Figure 3: Stack of particles at 12.5s (a) and 17.5s (b).
Figure 3: Stack of particles at 12.5s (a) and 17.5s (b).

Other important results of the study:

  • Particulate solids are complex systems to model, which is why it’s often necessary to resort to simplifications;
  • Corn kernels have an irregular shape that should be appropriately represented in the DEM software simulation;
  • It was only possible to calculate the rolling resistance coefficient when the corn kernels were represented as polyhedral particles;
  • The results with polyhedral particles were more accurate than those obtained with spherical particles, since the form used in the simulation is closer to the actual shape of the grains.

How does Rocky DEM work?

Rocky DEM quickly and accurately simulates the flow behavior of bulk materials with complex particle shapes and size distributions. By providing a unique platform for all types of processing industries, Rocky DEM allows scientists to computationally analyze their processes by mapping the material and geometric dynamic interaction of variables.

Rocky models the system as accurately as possible using Discrete Element Modeling (DEM). DEM is essentially a first major physical method that treats each particle of a granular layer individually. Each particle is represented by a specific shape and size that interacts with other particles and with the geometry of the equipment.

This ESSS software can accurately describe the contact behavior of each individual particle by using the various literature models available. All the forces acting on a particle are added, and particle acceleration is calculated. By numerically matching this with time, the velocity and position of the particles can be obtained. This process allows the user to visualize and predict the temporal and spatial evolution of the granular system.

In addition, Rocky provides the latest post-processing tools to help visualize and quantify a wide range of different metrics, including velocity, pressure and strain fields, dust consumption rates, material breakage, contour wear, and temperature variation. Engineers get a deep insight into processes.


Rocky DEM

Rocky DEM is a powerful, 3D discrete element modeling (DEM) program that quickly and accurately simulates particle behavior within a conveyor chute, mill, or other materials handling system. Rocky analyzes media flow patterns and energy absorption rates, particle breakage, and energy spectra analysis. The software optimizes life expectancy of conveyor belts and components, minimizes material spillage in a design, and reduces the need for dust control and suppression, among numerous other applications. This software is a revolutionary way to handle a problem through computer simulation.

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