Fig. 2: Pressure and shear stress close to the exit.

For the exit width b = 3.00D_m: a Plot of time-averaged contact and social pressure P_c (red circles) and P_s (blue squares), respectively, as a function of the desired velocity v⁰. As a reference, the total pressure contribution divided by two is plotted (black stars), showing a monotonic linear increase with v⁰. b Plot of time-averaged the deviatoric part of the contact and social stress τ_c (red circles) and τ_s (blue squares), respectively, as a function of the desired velocity v⁰. The total deviatoric part of the stress is shown as a reference (black stars). Inset: the fraction of shear stress from the social interaction, τ_s/τ_t (blue squares), or from the contact, τ_c/τ_t (red circles). In both a and b, including the inset, orange and green lines have been included to distinguish the faster-is-faster (FIF) from faster-is-slower (FIS) behavior. Error bars depict the standard deviation values.