Leonardo's universal friction coefficient is found to be universal after all!

It turns out that friction coefficient 0.25 suggested as universal by Leonardo da Vinci more than 500 years ago has some universaility, as minimum friction coefficient for any granular material: it makes me proud as italian ;) I guess it would be interesting to show this experimental result also theoretically or numerically, any interest? [HTML] Da Vinci's friction for granular mediaA Miron, R Tadmor, V Multanen, S Pinkert - Scientific Reports, 2025The concept of friction was integrated into the broader field of tribology in the 20th
century. Here, we revive the older friction coefficient concept and show that it is the
defining parameter for a family of granular materials. We show, for the first time, that … Regards Mike