Performance Estimation of a Flapping Foil Under Unsteady Upstream Flow Conditions

For a system of two flapping foils in tandem formation, the follower can achieve a surplus if its location and trajectory are adapted to the wake of the leader. The most common approach to evaluating the performance of the back foil for a range of conditions is to carry out a large number of numerical simulations, which can lead to accurate solutions but, on the other hand, can be computationally expensive. Although there is a large existing literature about the topic, the physics of the operation are not completely understood, especially when the foils are subjected to highly-unstable flow conditions or unusual kinematics, such as non-sinusoidal motions. In this study, the authors aim to estimate the thrust and efficiency performance of a foil subjected to an in-line tandem arrangement using a range of theoretical and Machine Learning approximations. This could lead to a quick evaluation method that would provide deep information about the physical characteristics that are responsible for the performance augmentation, helping with the understanding of atypical cases, which would lead to a great increase in the range of applications of tandem flapping foil arrangements.