Particle dynamics simulations are used for modelling systems that process materials consisting of numerous particles. In such cases, the number of particles can be remarkably large, but the composition and behavior of the mass can still be far from a fluid-like continuum flow. In such a situation, it is recommended to use, for example, a DEM (Discrete Element Method) approach instead of or in addition to FEM, MBD or CFD calculations. DEM analysis makes it possible to study a wide range of industrial processes related to the handling of solids.
Particle dynamics simulations can be used for studying particle disintegration, wearing of themselves and their wearing effects on structures. It is possible to simulate particles of arbitrary shape, but on the other hand, a simplification of large particle quantities into representative particle packages can be implemented too. The particle dynamics model can be coupled to a strength calculation model (FEM), in which case the static and dynamic loads caused by particles on the mechanical structures can be solved. The particle dynamics model can also be coupled to a flow simulation model (CFD or LBM), in which case the effect of particles on the behavior of a liquid or gas can be considered. The material containing particles does not have to be fully dry in the DEM model, since with the help of cohesive forces or the SPH model (soft particle hydrodynamics) it is possible to model material with some liquid content.
The granular mass can be mixed for processing purposes or modified and dispersed more evenly by drumming. In such processes, DEM modeling can provide answers to the following questions:
In some processes, the purpose is to sort and separate different particles from each other according to their sizes, types and densities. DEM modeling can be utilized in a simulative evaluation of the following:
Similar analyses can also be performed by using CFD simulations, but DEM or DEM-CFD coupling enables consideration of different particle geometries better and in a more efficient way.
Crushing and sorting hard material is an essential process in the mining industry and civil engineering. DEM modeling has been developed to include modeling of the breakage of particles of different shapes. It is possible to:
Granular material produces a different kind of load on structures than a liquid, since the load is redistributed as particles are mutually interacted and interrelated. In a particle bed, for example, vaulting and channeling can occur. Even though silos and vessels are typically assessed by means of FEM analysis, DEM modeling can reveal in more detail the true existing loads caused by a particle bed. DEM analysis can be used as a tool for obtaining:
Conveyors can experience accidents, and abnormal events can occur on line systems. Dynamic loads on structures are also linked to the particle mass being transported, which accumulates in different ways.
Fluidized beds can be utilized in combustion and chemical process technology. By coupling DEM assessments to CFD models, more accurate information about particle-level phenomena can be obtained than with a CFD simulation with granular material alone.
In industrial reactors, solids are often mixed with liquids, and the shape of the particles can vary significantly from the ideal and change as the process progresses. It is often necessary to use simulation to monitor the movement of particles in the reactor. Simultaneously the risk of drift accumulation or possible void volumes can be recognized. DEM modeling makes it possible to define more realistic particles in the CFD model. Possible applications are the following:
Sometimes the viscosity of the fluid being processed is so far from that typical for liquids that it begins to resemble a soft granular solid. In such a case, DEM simulations can be applied to consider the cohesive forces between the particles. This makes it easier to get a DEM model to reflect reality better than a CFD model defined using a corresponding demanding viscosity model. By applying cohesive forces in DEM simulation model, it is possible to:
The video simulates phenomena related to the transport of a sticky substance, including adhesion and clumping.
This analysis can also be used to determine material parameters (pile angles, wall friction, cohesion) for use in other simulations.
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Veli Pellikka
tel. +358 40 764 5763
veli.pellikka@stressfield.fimarkuk.fi
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