Effect of hydrodynamic wakes in dynamical models of large-scale fish schools

A novel hydrodynamic model of the wake of a swimming fish is developed and incorporated into a dynamical model of a fish school to explore the effect of hydrodynamics on the emergent behavior in schooling fish. The model incorporates well-established rules for attraction, alignment, and visual detection via a force-momentum balance in the surge, sway, and yaw directions, thereby allowing us to include the effects of body size, shape, and inertia into the dynamics of fish swimming in a plane. The key novelty of the model lies in the modeling of the hydrodynamics, which includes not only the potential flow induced by the body of the fish but also the vortex wakes generated by the fish. These hydrodynamic features, as well as the surge, sway, and yaw force coefficients, are parameterized via three-dimensional high-fidelity direct numerical simulations of a carangiform swimmer, thereby enabling a higher degree of realism in these models. The model is used to examine the effect of wake characteristics on the topology and movement of fish schools. The simulations indicate that these wake vortices lead to improved organization within the schools, especially in situations where the social forces are relatively weak.