Granular Particle Modelling with SimScale Particle Analyses
What are Granular Particle Analyses?
A simple definition of a granular material is a conglomeration of distinct macroscopic solid particles such as sand, nuts, coal, rice, coffee, grain, or corn.
Having a multitude of industrial applications, granular analysis is important because it is rooted in classical analysis methods, however, granular materials are considered as a new material form, different from solids, liquids, and gases. The motion of the particle follows Newton’s equations, where repulsive forces between particles are non-zero only when there is a contact between particles. 
The granular material must be large enough to avoid thermal motion fluctuations. Conventionally, the lower size limit of the granular material is about 1 µm. Powders are a special class of granular material due to their small particle size. This makes them more cohesive and more easily suspended in a gas.
Particle modeling considers the static and dynamic behavior of different types of granular materials. Depending on the industrial process that is to be analyzed, one can simulate the transport of a discrete phase within an incompressible fluid flow or the simple moving and separating process like in a screw conveyor or in a mill. Particle simulation can help engineers to design the particle equipment profile as well as accelerate and drive the particle process efficiently.
A Wide Range of Applications
Generally, two modeling methods for particle flow can be applied: the Discrete Element Method (DEM) for industrial bulk solids systems and the Discrete Phase Model (DPM) for the transport of a discrete phase within an incompressible fluid flow simulation.
Both DEM and DFM are used in a wide range of industries, including mining, metals processing, pharmaceuticals, construction and agricultural machinery, food and consumer goods, and chemical processing to simulate and analyze the performance of bulk particle handling and processing equipment – from powders and granules to ore, grains, tablets, fibres and more.
Process modeling of industrial bulk solids systems presents a challenging opportunity with regards to understanding the underlying physics, scaling lab-scale models, obtaining detailed large-scale data and balancing computational simplicity with the required rigor to accurately predict the actual behavior.
Moreover, due to market globalization and related efficiency reasons, the design and development process of bulk material handling equipment is often characterized by a fast construction phase, where the major risk is an improper design. Furthermore, the process of designing special production equipment like large conveyor plants cannot be standardized.
The usage of Discrete Element Simulation in the field of bulk solids handling equipment provides possibilities for the optimization of the design and the operating conditions as well as a view of the wear characteristics. 
In the vast majority of natural or industrial processes concerning granular materials, a secondary fluid phase — such as air — is present and its effects like fluidization (aeration of particles by gas injection) play an important role. 
Why Particle Analyses with SimScale?
The main benefit offered by particle simulation for engineers is related to improving the understanding the system and enabling virtual prototypes of bulk solids handling and processing equipment. Virtual prototypes can help optimize material usage and troubleshoot difficult particle processes.
You can find several particle analyses in SimScale Public Projects that can be used as free templates for any community member.
Mill profile particle analysis
One of the most recent simulations uploaded in Public Projects is a “Particle analysis of a mill profile”.
The objective of this project was to find a better profile for the mill, in order to produce specific acceleration characteristics for the particles. The CAD model contains the geometry of the mixing mill (solid part) and the volume where the particles are inserted by the filling algorithm. A mesh is not needed for this analysis type. The outer shape of the mill geometry is extracted automatically and used as boundary for the particles.
The filling is done at the beginning of the computation. In this case, the half of a cylinder geometry is used. At the beginning of the simulation, the particles fall to the ground because of the gravitational load. The mill does not move at that time (t<0.5s). After the particles come to a rest, the acceleration process is started. The mill is accelerated constantly so that the angular velocity (rad) is proportional to the time. The angular velocity can be adjusted either via a formula or a table value. For industrial applications, it is important that the particles inside the mill slide from the top to the bottom part during the mill rotational movement and do not fly around causing damage or fracture. This particle simulation can help the engineers to design the mill profile as well as accelerate and drive the mill efficiently.
Impact of blade shapes for mixing mills
The main purpose of this analysis was to study the impact of the blade shapes for different mixing mills. 
- Three different designs were uploaded and a discrete particle analysis set up.
- The transient particle analysis was carried out on 16 core machines which took around 6 hours each.
- A video animation of the three different mill types is shown in this YouTube video.
Particle flow analysis of a cyclone separator
Another very interesting project from SimScale shows how to simulate a particle fluid flow through a cyclone separator .
- The mesh was prepared locally and directly uploaded to the platform. The simulation was set up using the discrete phase model applying a k-Eqn LES turbulence model.
- The particles within the flow were modeled applying a four-way coupling method with 1000 kg/m^3 particle density.
- The simulation was carried out on a 32 core machine and took around 10 hours. An animation of the results is shown in this YouTube video.
Want to learn more about simulation with SimScale? Download this booklet.
 – Duran, J., „Sands, Powders, and Grains: An Introduction to the Physics of Granular Materials”, Springer-Verlag New York, 1999.
 Katterfeld, A., Gröger, T. – „Verified Discrete Element Simulations of Bulk Solids Handling Equipment”, Spring Meeting & 2nd Global Congress on Process Safety, 2006
 Kloss, Ch., Goniva, Ch., Aichinger, G., Pirker, S. – „Comprehensive DEM-DPM-CFD Simulation – Model Synthesis, Experimental Validation and Scalability”, Seventh International Conference on CFD in the Minerals and Process Industries CSIRO, Melbourne, Australia, 2009.
 Fisher, A. – “Mill profile particle analysis”, SimScale Projects, 2015
 Fisher, A – “Particle Mixing Mill”, SimScale Projects, 2015
 Szoeke, R. – “Screw conveyor”, SimScale Projects, 2015
 Holami, G. –“Particle flow analysis of a cyclone separator”, SimScale Projects, 2015