We work on the prediction and flow dynamics of flapping foil propulsion. This research topic is inspired by the locomotion of aquatic creatures employing flapping fins and appendages. We developed a numerical model based on BEM to predict the performance of flapping foils incorporating the alternating shedding of leading-edge vortices (LEV), which is a main element of difficulty in previous analysis of flapping foils with large motions. The developed method is compared with experiments, and the inclusion of LEV significantly improves the prediction, obtaining excellent agreement with measurements over a broad range of flapping motions. We further solved for the optimization of flapping motion to achieve maximum efficiency under specified thrust. An important finding here is that add odd higher harmonic component to the flapping motion increases the propulsion efficiency significantly. The study is important for the design of flapping foils as the next-generation propulsion system for water vehicles.

Publication:

Pan, Y., Dong, X., Zhu, Q. and Yue, D.K.P. 2012, Boundary-element method for the prediction of performance of flapping foils with leading-edge separation, Journal of Fluid Mechanics, 698, 446-467. (PDF)