Physics reveals that solid bodies have the property of getting stuck when they are forced to pass through a narrowing, producing an arc that blocks the exit. A common example is the stampede of people in mass events or the unloading of industrial silos. Bruno Guerrero (Venezuela, 33 years old) has studied clogging phenomena in his doctoral thesis thesis and has studied in depth how vibration affects the stability of the arches that obstruct the exit of a silo.

The work developed by Guerrero and collaborators is the first experimental research to analyse the dynamics of long-term traffic jams and has worked with a prototype industrial silo. "Our silo is a two-dimensional transparent container that resembles an hourglass, filled with spheres and anchored to an electromagnetic stirrer that is able to provide a controlled vibration. A camera financial aid records the region where the clogging occurs and, through image processing, identifies the arc manager of the blockage over time," says researcher.

The main conclusion of this research is that, when jamming occurs, the arches follow intermittent dynamics and gradually deform into different configurations. "Regardless of the vibration intensity applied, the perturbation tends to destabilise the arches, even for those that resist vibration. And while the initial shape of the arch affects its stability, it is the successive deformations that ultimately dictate its outcome written request ".

Another result finding of this study is that arches that do not break - despite vibration - do not have any dynamic or structural characteristics that differentiate them from those in which vibration facilitates unblocking. On the other hand, "long-lasting arches show clear signs of ageing: the effects of report persist and relaxation slows down over time".

Bruno Guerrero considers that the programs of study of clogging in granular media can be extrapolated to more complex situations such as the obstructions that occur in colloids (for example, the training of microthrombi in myocardial capillaries) or in active subject (bacterial colonies, herds of animals, vehicular traffic or autonomous robots) when passing through narrow channels.

Bruno Guerrero continues his research on the phenomenon of unblocking, in particular the transition to clogging, and its dependence on the discharge hole and the characteristics of the vibration applied.

Bibliographical references

- B.V. Guerrero, B. Chakraborty, I. Zuriguel, A. Garcimartín; (2019) Nonergodicity in silo unclogging: Broken and unbroken arches Phys. Rev. E 100, 032901. DOI: 10.1103/PhysRevE.100.032901

- B.V. Guerrero, L.A. Pugnaloni, C. Lozano, I. Zuriguel, A. Garcimartín; (2018) Slow relaxation dynamics of clogs in a vibrated granular silo, Phys. Rev. E 97, 042904. DOI: 10.1103/PhysRevE.97.042904