Perspective on the paper: GDR MiDi. On dense granular flows

The study "On dense granular flows" by GDR MiDi, published in 2004 in The European Physical Journal E 14, 341-365, stands as a seminal collective work that significantly advanced the understanding of dense granular materials. Remarkably, the names of the contributing authors are not listed; only the name of the consortium is given-a brave statement for joint efforts like this!. The GDR Midi (Groupement de Recherche sur les Milieux Divisés) was a CNRS-led consortium of French laboratories. Its mission was to bring together diverse scientific communities-including solid mechanics, fluid mechanics, physics, and geophysics-around the study of granular media, in order to promote collaboration through frequent, informal meetings held typically four times per year (see group photograph of a meeting in Carry Le Rouet in 2005). This approach enabled the identification of key scientific challenges as the need to compare and consolidate data across different configurations, between experiments and simulations, and across different research groups, ultimately inspiring the work that led to the collective GDR Midi paper.