Course Outline

• Introduction (1.5 - 2 hours)
• Industrial and natural flows
• Classic experiments and flows (shutes, tumblers, funnels, conveyors)
• Classification of powders (what is a powder/granular material?)
• Fundamental forces/interactions (particle-scale interactions, adhesion, capillarity, friction)
• Collective behavior (mixing, segregation, jamming)
• Stress propagation in powders (1.5 - 2 hours)
• Scaling analyses (density, gravity, friction, cohesion)
• Constitutive equations of freely flowing powders
• Cohesive granular rheology
• Role of polydispersity from ideal from non-spherical particles
• Wall friction
• Simulations of powders/granular media
• LAMMPS/DEM tutorial (1.5 - 2 hours)
• Scaling, microstructure, force chains, and other micro-to-macro scale calculations from simulations (1.5 - 2 hours)

Course Description

Everything flows – and so does powder! Powder rheology offers adequate tools for imitating the manifold powder handling processes out there - from silo discharge where different normal stresses act on the individual particles resulting in their stress-dependent flow behavior, over to dispersion processes where particle clusters need to be separated homogeneously by a fluid and all the way to the powder coating process during which powders are fluidized to overcome their bulk solid character for better transport properties. This short course comprises a theoretical part as well as a hands-on session.

The theory part covers an introduction to particle technology and what governs powder flow and all the different tests both static and dynamic in nature which can be done on a modern air-bearing rheometer which includes tests such as: fluidization, shear testing, wall friction , permeability tests, fluidized bed viscosity, pressure drop, envelope density, etc. Special attention will be given to shear testing and its underlying Mohr Coloumb theory – typically rather new for people coming from rheology. All test methods and their interpretation are explained along with material-specific examples: battery powders, laundry detergent, pharmaceutical samples. Different case studies will be discussed which will show the power of combining testing to solve real life processing challenges.

Additionally a hands-session will give you a chance to experience how to handle powders and perform measurements with them. Participants will perform their first shear and cohesion strength measurement and discuss the results with the teacher.