Active particles with desired orientation fowing through a bottleneck

Abstract

We report extensive numerical simulations of the fow of anisotropic self-propelled particles through a constriction. In particular, we explore the role of the particles’ desired orientation with respect to the moving direction on the system fowability. We observe that when particles propel along the direction of their long axis (longitudinal orientation) the fow-rate notably reduces compared with the case of propulsion along the short axis (transversal orientation). And this is so even when the efective section (measured as the number of particles that are necessary to span the whole outlet) is larger for the case of longitudinal propulsion. This counterintuitive result is explained in terms of the formation of clogging structures at the outlet, which are revealed to have higher stability when the particles align along the long axis. This generic result might be applied to many diferent systems fowing through bottlenecks such as microbial populations or diferent kind of cells. Indeed, it has already a straightforward connection with recent results of pedestrian (which self-propel transversally oriented) and mice or sheep (which self-propel longitudinally oriented).