A strongly coupled 3D BEM-FEM fluid–structure interaction model for the analysis of flexible biomimetic thrusters

Biomimetic propulsors that emulate the kinematics of famous thunniform swimmers, such as the Bluefin tuna and the humpback whale, offer an eco-friendly alternative to conventional propellers for autonomous underwater vehicles. Their advantages include low-frequency operation, advanced maneuverability, and high efficiency during long-distance cruising. Related research suggests that elasticity, advanced control, and properly tuned material parameters are key for emulating nature in thruster applications. The present work proposes a strongly coupled fluid–structure interaction model that addresses the hydroelastic response prediction problem, supporting the design of flexible flapping-foil thrusters. The developed 3D FSI model consists of an unsteady boundary element method for the lifting-surface problem and a finite element method, based on Discrete Kirchhoff Triangles for thin plates with stiffness variation, for the structural problem. The response of elastic wings is implicitly non-linear since deformations affect the hydrodynamic load excitation and vice-versa. Therefore, strong coupling is crucial for accurately capturing the underlying physics. Comparisons against experimental data support the validity of the developed FSI numerical scheme, suggesting that it can facilitate the design of concept thrusters with enhanced performance using optimization and elastic parameter tuning. • Hydroelastic performance of flexible biomimetic thrusters. • Flapping wings with variable flexural rigidity. • GPU-accelerated fluid–structure interaction solver. • Efficiency enhancement via passive deformation and optimality.