Granular Matter Webinar Series

The Editors of Granular Matter are proud to present a series of webinars organized by the journal.

Next Webinar Coming Soon

If you have any questions, contact Jack Manzi at


Glass half full: Embracing the unexpected in granular systems

Speaker: Prof. Christine Hrenya, University of Colorado at Boulder

Originally Presented on: 22 October 2020

Recording: View a recording of the webinar here.

Granular and multiphase systems containing solid particles display a host of behaviors unlike those of their single-phase counterparts.  The unexpected behaviors are often at odds with current hypotheses, which ultimately leads to a greater physical understanding.  In this talk, results from our investigations into liquid-coated particles, clustering instabilities, and cohesive-particle flows will be presented.  Each topic will be discussed in chronological order, revealing the unexpected results we encountered, the hypotheses we developed to explain said behaviors, and the testing of these hypotheses until a a physical understanding emerged that we were confident in.  This presentation echoes considerably the material covered in the 2020 van 't Hoff lecture (September 2020, TU Delft Process Technology Institute), with modifications to target the Granular Matter webinar audience.

How to Convert a Nano-powder into a Nano-crystalline Solid

Speaker: Prof. Dietrich E. Wolf, University of Duisburg-Essen

Originally Presented on: 22 September 2020

Recording: View a recording of the webinar here.

Largely unnoticed by theoretical physics, the last 20 years have seen a revolution in nano-particle processing. One example is that powders - although very porous, when freshly produced - can be converted into a dense solid, which still keeps a microstructure at the nanoscale. The processes are new developments related to what traditionally was called "Spark Plasma Sintering", but has nothing to do with sparks and plasmas. Computer simulations predict intermediate steps of these processes and reveal the underlying mechanisms. I will give a review of recent simulations, with a focus on so-called flash-sintering.

Repulsion and rotation: Penetrating granular matter near a wall

Speaker: Ernesto Altshuler, Group of Complex Systems and Statistical Physics, Physics Faculty, University of Havana

Originally Presented on: 28 August 2020

Recording: View a recording of the webinar here.

How a solid object penetrates granular matter near boundaries has been rarely studied. In this seminar I will describe detailed experiments showing how a cylindrical object penetrates into a granular bed near a vertical wall. We find two kinds of motion: the intruder separates from the wall as it sinks, and rotates around its symmetry axis. The repulsion is thought to be caused by the asymmetrical loading of force chains, which are stronger between the object and the wall. The rotation is associated to the tangential friction between the grains and the intruder --a fact that has been neglected in previous research. We introduce simple phenomenological models to explain both motions, and DEM simulations to further explore the parameter space. Moreover, we experimentally show the analogy between the penetration of two intruders released side-by-side far from boundaries, and one intruder released near a vertical wall, which suggests the idea that the method of images might be useful in the field of granular matter.

Ref: V. L Díaz-Melián, A. Serrano-Munoz, M. Espinosa, L. Alonso-Llanes, G. Viera-López and E. Altshuler, Phys. Rev. Lett. 125, 078002 (2020)