We investigate the avalanches of spherical and non-spherical granular particles inside half-filled rotating drums. The time series of the center of gravity of the particle assemblies are obtained via image analysis and their single-sided amplitude (SSA) spectra are analyzed. The spectra features of this new indicator turn out to be characteristic for the avalanches, in terms of the existence of peaks in the low-frequency range and the decay rate of high frequency components. The SSA spectrum has a peak for the packings of non-spherical particles but not for the spherical particles. The high frequency part is characterized by a power law decay { $1/f^a \ (a>0)$ }. A $1/f$-decay is found only for the spherical particles. For the packings of cornered particles, the exponents significantly deviate from $a=1$. As $1/f$ spectra are often associated with self-organized criticality and therefore a scale invariance of the dynamics, we may conclude that there is no scale-invariant structure for granular avalanches. Considering the small number of particles and the regularity of convex particle shapes being used, the spectral features revealed in this study could be utilized for validating particle simulations.

Experimental study of particle shape dependence of avalanches inside a rotating drum

As a follow-up of an earlier work on the numerically exact Coulomb friction in two-dimensional simulations, we present here the relations and implementation for three-dimensional discrete element particles.

Implementation of numerically exact Coulomb friction for discrete element simulations in three dimensions

Poster Session

poster

[EPJ Web of Conferences, Volume 249 (2021)](https://www.epj-conferences.org/articles/epjconf/abs/2021/03/contents/contents.html)

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Powders & Grains 2021

Powders & Grains 2021 will be held in Buenos Aires (Argentina, VIRTUAL) July 5, 13, 21, 29 and Aug 6, 2021. The aim of the conference is to give an up-to-date picture of the broad research field of granular media, powders and grains. Contributions from experts around the world will focus on research topics that cover a wide range of open problems in the field.

**Session Chairs:**
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<br>Guilhem Mollon and Manuel Carlevaro

Dominik Krengel

2

6

Presentations

Experimental study of particle shape dependence of avalanches inside a rotating drum

Implementation of numerically exact Coulomb friction for discrete element simulations in three dimensions

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