Hydroelastic analysis of flapping-foil thrusters using a partitioned BEM-FEM

Understanding the mechanics of aquatic locomotion has been an active field of research for decades and continues to inspire technological solutions ranging from small-scale propulsion systems for autonomous underwater vehicles (AUVs) to larger-scale energy saving devices (ESDs) for ships. The bio-inspired thrust-producing kinematics are shared among most flapping-foil systems, however joint experimental and numerical research suggests that incorporating additional biomimetic features, such as hydrodynamic shape and elasticity, in new designs can enhance the efficiency. Focusing on the latter, the response of passively deforming wings is implicitly non-linear, since deformations affect the hydrodynamic load excitation and vice-versa. Therefore, fluid-structure interaction simulations are essential for accurate predictions of the wings’ response. In the present work, a cost-effective computational tool is proposed for the hydroelastic analysis of flexible flapping-foil thrusters, which consists of a 3-D unsteady boundary element method (BEM) weakly coupled with a finite element solver (FEM) based on plate elements. The verification of the present method is accomplished by means of comparison against experimental data from the literature. The prediction capabilities and the limitations of the weakly coupled BEM-FEM are discussed. Finally, the proposed numerical tools serve as the building blocks for the fully coupled BEM-FEM scheme that is currently under development.