Livio Gibelli

Research Fellow, University of Warwick

I am currently working as a research fellow in the University of Warwick School of Engineering (Coventry, UK). I received my PhD in applied mathematics from the Politecnico di Milano and, prior to my current position, I have been an assistant professor at the Politecnico di Milano and a research fellow at the University of British Columbia and Politecnico di Torino.

My main research interests include the mesoscopic approach to the behavioural social crowd dynamics, the kinetic theory modelling of non-equilibrium multiphase systems, the continuum description of slightly rarefied gas flows, and the numerical methods for solving kinetic equations.

AIMS Conference (5-9 July 2018, Taipei, Taiwan)

On July 5/9, I took part to the 12th AIMS Conference on Dynamical Systems, Differential Equations and Applications in Taipei.
This conference aims at fostering and enhancing interactions among mathematicians and scientist in general. It has featured 135 special sessions with a broad range of topics. Keynote lectures were given by famous mathematicians (A. Buffa, V. Calvez, S. Peng, J. Ball, just to cite a few).

AIMS Conference schedule at a glance

I was in particular interested to two special sessions devoted to kinetic theory: "Models and Numerical Methods in Kinetic Theory" (where I was invited to give a talk) and "Kinetic and Related Equations: Collisions, Mean Field, Organized Motion".
Although kinetic equations have been traditionally applied to rarefied gas dynamics and plasma physics, these special sessions have confirmed an emerging trend in kinetic theory, namely the use of its theoretical framework to study topics in fields which are apparently far from fluid dynamics like the emergence of organized collective behaviour in vehicular traffic, crowds, swarms, social systems and biology. This wide range of new applications and the benefits that these studies can potentially bring to the society has significantly revived the interest in kinetic theory.
A detailed description of sessions along with the abstracts of presented talk can be found at the conference's website (http://aimsciences.org/conferences/2018/).

Overall, I was pleased to partecipate to the conference. The only negative aspect was that typhoon Maria stroke Taipei the day I had to flight back home. As a consequence, my flight was delayed and I was forced to spend almost two days segregated in hotel!

2nd meeting of the "Multiscale and Non-continuum flows" - Special Interest Group (SIG)

On September 27th, the second Special Interest Group (SIG) meeting was hosted at the University of Warwick.

This series of meetings aims at bringing together theoreticians with experimental groups who share interest in the area of multiscale and non-continuum flows.
Beside the pleasure of seeing again many members of the Micro & Nano Flows group, the meeting was a good opportunity to meet other researchers across the United Kingdom.

After a welcome and 2-minute introductions by all the participants, four main lectures were given.
Dr. Kislon Voitchovsky (Durham University) discussed the liquid behaviour at nanoscale interfaces both from the numerical and, even more interestingly, experimental standpoints.
Dr. James Sprittles (University of Warwick) showed how non-equilibrium effects of the vapor flows can (unexpectedly) play a major role on the dynamics of the collisions between microdrops and  on their impact/spreading on solid surfaces.
Dr. Sergey Karabasov and Dr. Ivan Korotkin  (Queen Mary University of London) presented an interesting hybrid model which smoothly combines molecular dynamics with the Landau-Lifshitz fluctuating hydrodynamics.

I did appreciate the stimulating and constructive environment the meeting has created, as well as the main message of encouraging researchers to reflect on the impact that their studies may have beyond the academic community and to engage with industrial partners in collaborative research.

The chain fountain phenomenon

A chain fountain is the name given to the counterintuitive phenomenon where a long bead chain
appears to defy gravity by first leaping out of its container before falling to the ground.

This became known as the Mould effect, after a British science presenter, Steve Mould, who made the experiment famous with a video that went viral on YouTube.
Apparently, he discovered the chain fountain phenomenon while looking for a way to explain at the molecular level the capability of viscoelastic fluid to pour itself, the so-called open siphon effect.

In this funny TED talk, Steve Mould recounts his discovery and investigation into this entertaining and counterintuitive phenomenon.


The physics behind the chain fountain is non-trivial.

At first sight one could be tempted to explain the phenomenon by observing that the falling chain has downward momentum, causing an upward momentum in beads leaving the container. This, in turn, makes them leap before gravity can slowly reverse their momentum. However, if inertia causes the flowing fountain, the chain would be stationary at the top of the curve, while this is not the case.

It has been later proposed that the fountain is not driven by inertia, momentum, or gravity but rather by an anomalous push force exerted by the container on the link of the chain about to come into motion.
(http://rspa.royalsocietypublishing.org/content/470/2163/20130689).
The authors of the paper also posted a video on the Royal Society Youtube channel where the educational value of the demonstration and the analysis is highlighted.

Since it was first brought to widespread attention by Mould, many explanations of the chain fountain have been put forward and several papers have been published, even recently (http://aapt.scitation.org/doi/abs/10.1119/1.4980071, https://journals.aps.org/pre/abstract/10.1103/PhysRevE.89.053201, https://arxiv.org/abs/1612.09319).
However, a complete description of the mechanisms at play appears to be still lacking.

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