Performance of Semi-Active Flapping Hydrofoil with Arc Trajectory

The semi-active flapping foil driven by the swing arm is a simple structure to realize propulsion of foil. motion trajectory this mechanism circular arc, and its hydrodynamic characteristics are not clear. This paper systematically investigates working performance with arc track. Compared traditional structure, special design parameters mainly include length stiffness torsion spring. In paper, three-dimensional fluid-structure coupling method used solving fluid dynamics equation structural equation, different geometric analyzed. From results, increasing beneficial improving peak efficiency foil, also thrust coefficient corresponding point. Under certain length, reducing spring conducive system, but it adverse coefficient. Further analysis shows that maximum angle attack key factor affecting propulsion. For described in usually concentrated near αmax=0.2 rad. However, for kind propulsion, influencing factors relatively complex, including swinging arm, stiffness, advance remains range far from starting state.