Session: 05-09: Fluid Structure Interaction

Paper Number: 131341

131341 - Computational Study of In-Phase and Anti-Phase Interactions of Fish in a Phalanx School 

Fish have been observed swimming alongside each other with their snouts aligned on the same frontal plane, and adjusting their kinematics relative to their neighbors, when encountering high incoming flow speeds. The hydrodynamic performance of a fish swimming inside such a phalanx (parallel, or soldier) formation and its dependence on undulating phase variation within the school are the objects of this study. A three-fish phalanx school is used to examine the performances of both interior and edge fish. The three-dimensional (3D) fish models that make up the school are composed of a bodies and caudal fins with trout-like morphology. The undulating kinematics of each trout-like model was prescribed using a traveling-wave equation whose amplitude varied along the body length based on a quadratic equation. The flow around these undulating bodies was simulated using a direct-numerical simulation (DNS) solver using an immersed-boundary method (IBM). The temporal phase of the undulation of the middle fish was adjusted to examine two modes of interactions: in-phase and anti-phase. In-phase interaction occurred when all three fish performed synchronized undulation, and anti-phase interaction occurred when the middle fish undulated completely out of phase of its two neighbors. These modes of interactions had strong influences to the performances of the schooling fish and the mechanisms of these modes of interaction were examined. Larger schools have been seen formed by units of single-row schools, and therefore knowledge of the swimmer performance in the 3-fish phalanx can help understand hydrodynamics inside larger schools.

Presenting Author: Jiacheng Guo University of Virginia