Influence of wake interference on flapping dynamics of an inverted flexible foil

Due to a mutual interaction with a uniform flow, a flexible foil with its trailing edge clamped, also known as the inverted foil, exhibits a wide range of complex self-induced flapping regimes, such as large amplitude flapping (LAF), deformed, and flipped flapping. When placed in tandem with a bluff body in the upstream region, the foil’s proximity and wake flow patterns could impact the flapping dynamics. To study the coupled wake-body interaction and the self-induced response of an inverted flexible foil when placed in the wake of a circular cylinder, we carry out high-fidelity numerical experiments for varying gap distances. Our goal is to investigate the mechanism leading to the foil's self-sustained flapping response in the wake flow. In this study, we particularly attempt to answer the following questions: (i) How does proximity and wake interference influence the foil's flapping response at various separation distances, (ii) what is the intrinsic relationship between the wake vortices and different flapping modes, (iii) what is the optimal range of bending stiffness to sustain LAF response in wake flow compared to uniform flow, and (iv) how does the mass ratio and Reynolds number influence the LAF response in this arrangement?