The Granular Flow Module

The Granular Flow Module is used to model the bulk behavior or flow of granular materials. Granular flow simulations are used to model the behavior of macroscopic particles, such as sand, grains, powders, or pellets, when subjected to external forces like gravity, vibration, or shear. Unlike fluids or solids, granular materials can exhibit both solid-like and fluid-like behavior depending on their packing, confinement, and stress conditions. Granular flow is important in a variety of applications including pharmaceuticals, geotechnics, additive manufacturing, and food processing.

Most of the physics interfaces in COMSOL Multiphysics use the finite element method (FEM) to compute fields such as temperature, fluid velocity, electric potential, concentration, or displacement. In contrast, granular flow provides a Lagrangian description of a problem, in which the particles are treated as discrete entities that can interact with external fields, with boundaries in the surrounding geometry, and with each other. Granular flow is based on the discrete element method (DEM) which treats the particles (referred to as grains) as spheres (3D) or cylinders (2D) occupying space in the computational domain.

Grains are allowed to collide with each other and with the boundaries (walls). Contact force models are utilized to determine the resultant grain deformations and contact forces. Their trajectories are computed in the time domain by solving a set of equations based on the Newton’s laws of motion. Both translational and rotational degrees of freedom are accounted for and are updated every time step based on the forces and torques resulting from contact and external fields.

Heat transfer effects on the grains can also be included by tracking the temperature of each grain. A grain’s temperature can change due to an external heat source, convective heat transfer with the surroundings and conductive heat transfer due to grain-grain and grain-wall contacts.

The Granular Flow Module also offers a wide variety of release mechanisms to control how the grains are inserted into the geometry. Grains can be released directly into the domain or along the boundaries. By default, grains are released such that they do not overlap with other grains or walls. After the simulation is complete, many dedicated tools for visualizing grain motion and reporting grain statistics are available.

The Granular Flow Module supports simulations in two and three space dimensions.