Effective friction of granular flows made of non-spherical particles Ellák Somfai, Dániel B. Nagy, Philippe Claudin, Adeline Favier, Dávid Kálmán and Tamás Börzsönyi EPJ Web Conf., 140 (2017) 03062 Published online: 30 June 2017 DOI: 10.1051/epjconf/201714003062