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Granular Flows: Fluidization and Anisotropy

Promotor: Prof.dr. M.L. van Hecke

G.H. Wortel
19 november 2014
Thesis in Leiden Repository

This work discusses the flow of granular materials (e.g. sand). Even though a single particle is a simple object, the collective behavior of billions of particles can be very complex. In a surprisingly large amount of cases, it is not exactly known how a granular material behaves, and this while these kinds of materials are omnipresent in everyday life, industry, and nature Similar to materials such as water, which can occur as ice, liquid water and vapor, sand can also exist in different phases of matter. If you for instance walk on the beach, sand behaves like a solid, but if you pour it out of your shoes afterwards, it flows like a liquid. This thesis is dedicated to experiments where we investigate what happens when you try to “liquefy” sand by weakly vibrating it. We use an experimental setup which enables us to study how much stress is required to make sand flow, depending on the desired flow rate and the amount of vibrations. These experiments reveal several physical principles that turn out to be important towards understanding the unique behavior of these kinds of materials.