Investigating the Dynamics of Airfoil Propulsion to Study the Collective Motion in Aquatic and Avian Animals*

The present study investigates the self-propulsion fluid dynamics of oscillating airfoils to understand the unique collective motions observed in aquatic and avian animals. Here, the computational fluid dynamics simulations are performed on heaving NACA0017 airfoil in both single and tandem arrangements. The heaving airfoils' ability to generate propulsive forces is evaluated at different heaving frequencies. In addition, in-house experiments are conducted on the airfoils with aspect ratios of 3 and 4.5 to validate the numerical observations. The simulation results of tandem airfoils indicate the formation of the stable equilibrium gap between the airfoils at the induced velocity wavelength downstream of the trailing airfoil. Furthermore, this equilibrium gap is closely linked to the frequency and amplitude of heaving kinematics. Our results indicate that the use of multiple airfoils can effectively enhance velocity while simultaneously reducing energy consumption. These findings provide insight into the basic principles that control coordinated group motions in nature and open up opportunities for additional investigation into self-organization in these complex biological systems. The flow structure and aerodynamic forces will be thoroughly discussed in the presentation.