Lattice Boltzmann simulations of deformation and efficiency of a chord-wise flexible wing in a free stream flow

Flapping of a chord-wise flexible wing in a steady free stream is studied by using a lattice Boltzmann flexible particle method (LBFPM) in a three-dimensional space at a chord based Reynolds number of 100. The flexibility and wing mass ratios are systematically varied, and their effects on aerodynamic forces and power efficiency are explored. It is demonstrated that large the deformation is controlled by the wing and fluid flow inertia (``added mass) and the wing flexibility. A dynamic balance between the inertia and the appropriate level of the flexibility allows the flexible motion in phase with the driving base and have a much larger rotational velocity or rotational momentum than a rigid wing, resulting in a better performance.