Non-local rheology in granular media: a perspective on the 2015 EPJE Paper by Bouzid et al

The study "Non-local rheology in dense granular flows: Revisiting the concept of fluidity," published in 2015 in The European Physical Journal E (vol. 38) by Mehdi Bouzid and collaborators, stands as an important contribution to the rheology of granular materials. In their work, the authors critically discuss the differences between proposed non-local models and provide clear pathways to discriminate between them. This perspective paper revisits the state of the art at the time of the Bouzid et al's publication, highlighting its role in inspiring subsequent research. We then explore recent advancements since 2015, which, while significant, have not yet fully resolve the questions originally raised by Bouzid et al.