Granular Flow Module

Define Grain Properties and Species

With the Granular Flow Module, it is possible to specify grain size, density, and stiffness and coefficients of restitution and friction, as well as introduce rolling resistance or adhesive forces for fine powders. Grain shape is treated as spherical in 3D and cylindrical in 2D, with translational and rotational degrees of freedom resolved at each time step. Multiple grain types can be defined in the same model, either as distinct species or drawn from size distributions, making it possible to capture segregation and mixing effects in polydisperse systems. Thermal properties such as specific heat capacity and conductivity can also be specified when including heat transfer.

Collision and Contact Models

The module provides detailed control over how grains interact, with the option to choose between linear elastic, Hertz–Mindlin–Deresiewicz (Hertz–MD), or Hertz–MD with adhesion models. Noncontact forces such as van der Waals interactions can be added to capture long-range cohesion. Rotational resistance can be modeled using constant or velocity-dependent torque options. For both grain–grain and grain–wall collisions, it is possible to customize restitution, friction, and damping coefficients. This flexibility enables customized contact behavior for different material types, from free-flowing pellets to cohesive powders.

Mixing, Segregation, and Packing Analysis

The Granular Flow Module can be used to model how particles segregate by size, mix in rotating drums or ribbon mixers, and are packed into beds or containers represented by CAD geometries. Built-in evaluation features provide quantitative measures such as the coordination number. In addition, customization options offer evaluation of packing fraction, porosity, and species concentration variance, enabling both microscale and macroscale analyses of bulk behavior. These measurements can be used to assess mixing efficiency, predict segregation patterns, and characterize the structural properties of packed beds. By combining detailed particle dynamics with statistical results evaluation, the module provides valuable metrics for process optimization.

Evaluate and Visualize Results

Results can be visualized as grain positions, trajectories, or full particle paths, with options to color grains by velocity, force, release time, temperature, or particle species.

Built-in evaluation tools, complemented by user-defined methods, enable the computation and visualization of quantities such as mass flow rate, wall pressure, packing density, porosity, and collision frequency. They also support statistical analyses, including histograms and averages of derived measures like coordination number and concentration variance. Animations highlight discharge, spreading, mixing, and segregation dynamics, while contour and field plots shed light on macro-level properties such as porosity and stress distribution.

These features make it possible to interpret particle-scale motion and bulk behavior in both qualitative and quantitative terms.

Particle Release and Inlet Features

Grains can be introduced from surfaces or volumes, with full control over their initial positions, velocities, and release rates. In addition to monodisperse cases, grains can be sampled from defined distributions of material properties and sizes or their initial conditions. Both continuous inflows and batch releases can be simulated, and multiple release features can be combined to represent different material streams. Random number generators ensure variability in position, velocity, or size, with options for reproducibility using fixed seeds. These options make it possible to replicate realistic feeding conditions in silos, hoppers, mixers, and conveyors.

Wall and Boundary Interactions

When particles collide with walls or leave a domain, their behavior can be customized: They can be allowed to pass through walls or completely removed via outlet conditions. Separate restitution and friction coefficients can be set for walls, and moving boundaries such as rotating drums, ribbon mixers, or vibrating sieves can also be modeled. Wall contact properties can even be defined per grain–wall pair, enabling simulations of heterogeneous systems with different wall materials or surface treatments.

Heat Transfer Between Grains and Walls

In addition to mechanical interactions, the module supports heat transfer modeling between grains and surrounding walls or external fields. Grain temperature is computed as an additional variable, assuming uniform temperature within each grain. Heat exchange includes conduction across contacts, convection with surrounding media, and external heat sources. Validity can be assessed using the Biot number, ensuring the assumption of uniform grain temperature holds for small, conductive particles. These capabilities enable studies of temperature-dependent processes such as powder spreading in additive manufacturing or thermal treatment of bulk solids.

Export and Import of Data

The Granular Flow Module offers a range of options for importing and exporting data to aid both model setup and results analysis. Grains can be initialized from tabular data files that define particle positions and velocities, with options for scaling, translation, and rotation. Initial distributions can also be imported from structured grids or automatically placed within CAD-defined domains for realistic packing or feeding conditions.

After a simulation has been run, results datasets provide access to full particle histories, including positions, velocities, radii, and derived quantities such as porosity, packing fraction, or collision statistics. Processed results like mass flow rates and wall pressures, as well as visualizations such as trajectories, colored fields, and histograms, can be exported as images, animations, or raw numerical data for further use in third-party tools.