Numerical study of wake induced vibration(WIV) and energy harvesting characteristics under different stable conditions

In order to better capture energy from natural water flow, we designed a novel captive energy model using wake induced vibration (WIV) combined with multi-stable theory. The model consists of an upstream stationary square cylinder and a downstream vibrating circular cylinder. The multi-stable characteristics are achieved by controlling the horizontal distance (l) and vertical distance (d) between the tip magnet of the vibrating cylinder and the stationary magnets. We simulate the capture energy characteristics of the harvester for different stable conditions at 0.1 m/s-0.8 m/s (i.e., 1990 ≤ Reynolds number ≤ 15,923) using the computational fluid dynamics (CFD) method. The simulation results show that when fixing l = 0.020, d = 0.016 and d = 0.017 are bi-stable systems, and at the same time, it will be trapped in a potential well at a flow velocity of 0.1 m/s, resulting in a lower amplitude and vibration frequency. When d is fixed at 0.017 m, l = 0.021 and l = 0.022 are tri-stable systems with a wider flow velocity interval corresponding to its high amplitude. Different magnet positions affect the phase between the lift coefficients and displacements of the bluff body. At flow velocities from 0.1 m/s to 0.4 m/s, the energy harvesting effect of the with-magnet system is better than that of the non-magnet system.