Collective dynamics and model verification: Connecting kinetic modeling to data

Scattering of flocks for an attraction-repulsion model

Andrea Thatcher

Arizona State University


We perform scattering experiments for two self-propelled particle based flocks. The dynamics of the flocks is governed by a pairwise interaction potential exhibiting short-range repulsion and long-range attraction. The model is parameterized by two parameters: the strength of the interaction potential and the speed of a uniformly translating flock. We prepare two flocks in the uniformly translating state with large initial distance and direct them towards each other. For the limit of two particles, there are two fundamentally different dynamic outcomes: In the high speed case the two particles interact for a very short time and then their paths diverge. In the low speed case, the particles get caught in a damped periodic orbit and merge into a single flock. We show that for N particle flocks a similar transition between merging and diverging flocks occurs, but now seen at lower speeds are trapped solutions. Specifically, we show the trapped double and single milling solutions and the merging and diverging flocks, and we describe the bifurcation diagram in the parameter space.