Wake Structure and Performance of Finite Aspect-Ratio Flapping Foils

Most wings and fins found in nature tend to be of low or moderate aspect-ratio. However, most experimental and numerical studies in this area of bio-hydrodynamics have focused on examining large or infinite aspect-ratio flapping foils. In the current study, an efficient, finite-difference based immersed boundary solver for computing flows with moving immersed boundaries has been developed to explore the wake structures and hydrodynamic performance of finite aspect-ratio flapping foils. The results of these numerical simulations indicate that the wake topology of these relatively low aspect-ratio foils is significantly different from that observed for infinite/large aspect-ratio foils. The simulations also allow us to investigate the effect of the foil aspect-ratio, Strouhal number, Reynolds number, and pitch-bias on the wake topology and foil performance.