A review on fluid dynamics of flapping foils

The fluid dynamics of flapping foils are reviewed in this article. A very wide range of researches are conducted for the two-dimensional flapping foil which has a relatively simple geometry. However, for a three-dimensional foil, the aspect ratio and shape take effects and completely distinct fluid dynamics are revealed compared with the two-dimensional one. This review gives a summary on the experimental techniques and numerical methods used in the researches on the fluid dynamics of flapping foils. The effects of some key parameters including Reynolds number, reduced frequency, flapping amplitude and three-dimensional effect on the fluid dynamics of flapping foils are reviewed. The researches focusing on the wake structures, aero/hydrodynamic characteristics and energy harvesting efficiency are discussed. Finally, some conclusions are drawn and potential future research directions are recommended.