Effects of deformation on lift and power efficiency in a hovering motion of a chord-wise flexible wing

To understand the effects of flexibility on aerodynamic force, the lattice Boltzmann flexible particle method (LBFPM) is employed to simulate deformation and its relationship with inertial and elastic forces in a flapping motion of a chord-wise flexible wing in a three-dimensional space at a hovering Reynolds number of Re=136. The rigidity EI and effective inertia Π0 are systematically varied, and lift, drag, deformation and power efficiency are computed and compared. It is found that both the rotational and translational inertia contribute to the deflection limited by flexural rigidity and result in a large angular and translation velocities, which generate a large intensity of vorticity and benefit lift and power efficiency. It is revealed that a “mirrored S” or “S” shaped deflection due to the rotational inertia plays a more positive role than the deflection caused by the translational inertia.