Energy Harvesting in the Wake of An Inverted C-Shaped Bluff Body

This paper proposes a novel wake-induced vibration (WIV)-based energy harvesting system consisting of two bluff bodies. An inverted C-shaped bluff body is stationary installed at the upstream position to generate an interference wake street, and a cylinder bluff body equipped with a transducer is elastically suspended at the downstream position to harness WIV energy. The hydrodynamics and energy harvesting (EH) performance of the proposed system are investigated via experimental studies. The reduced velocity (U*) ranging from 2 to 14 (the corresponding Reynolds number ranging from 15100 to 106200) is considered in the present study. It is found that the wake generated by the inverted C-shaped bluff body significantly affects the EH performance. Enlarging the opening angle (α) of the C-shaped bluff body increases the vibration amplitude of the downstream cylinder, thereby increasing the harvested power. When the spacing (L) between two bluff bodies is two times the cylinder diameter (D), the wake-induced vibration (WIV) mode is observed, while the combined WIV and wake galloping (WG) mode occurs when α is 150°, and L equals 3D or 4D. The average drag coefficient becomes negative when L is 2D, 3D, or 4D. By carefully configuring a C-shaped bluff body, the wake generated by it can bring an augmenting effect on the vibration of the downstream EH cylinder. For example, the RMS power output of the proposed EH system reaches a maximum of 0.31 W at U* = 8 and L = 4D, which is 300% greater than that of its traditional counterpart. Furthermore, after a number of case studies, it is identified that the proposed EH system can achieve the best performance when α is 150° and L = 2D.