This paper proposes an electromagnetic bi-stable energy harvester (EBEH) with tunable stiffness for scavenging the hydrokinetic energy from flow-induced vibration (FIV) scenarios. A mathematical model of the magneto-mechanical–electrical coupling system is established considering vortex-induced forces, wake oscillator effect, negative linear stiffness and hybrid excitations. The bi-stable system with adjustable barrier height is employed to enhance state-of-the-art energy scavenging performance of vortex-induced vibration (VIV). Preliminary verification with regard to VIV within a lock-in wind speed range has been implemented by means of CFD simulation. The nonlinear energy transfer capacity and energy conversion performance of the FIV based EBEH are evaluated under solitary vortex-induced vibration (VIV) and hybrid excitations. Simulation results show that EBEH with larger negative linear stiffness has higher energy conversion efficiency and target energy transfer capacity in a wide range of inlet velocities. The large amplitude and low frequency vibration of the VIV of the cylinder is mainly caused by the lift pulsation, meanwhile the small amplitude and high frequency galloping are caused by the perpendicular component pulsation of the drag force. The fluctuations of the lift/drag coefficient at different inflow velocities are directly related to the VIV or galloping amplitude of the cylindrical bluff body. Specifically, the frequency f_D is approximately twice the frequency f_L in a wide inflow velocity range; The amplitude of fluctuating lift exceeds 2.0 in a wide range of inflow velocity from 1.0 m/s to 20 m/s. The nonlinear energy transfer efficiency of the FIV based EBEH with smaller barrier height is greater than 60% when the inflow velocity ranges from 20 m/s to 30 m/s. The nonlinear energy transfer capability of EBEH with appropriate negative stiffness outperforms its counterpart of cubic stiffness more than ten times. The maximum mean harvested power achieved from EBEH can be increased over 900% than that of the cubic stiffness case. Regardless of negative stiffness alteration, the optimal external load that maximizes the EBEH output power is around 50 Ω. Additionally, when the vortex-induced vibration cannot be woken, intervention of base excitation causes considerable chaotic motion consisting of aperiodic intra-well and inter-well snap-throughs at low inflow velocities. Nevertheless, nonlinear energy transfer efficiency of bi-stable energy harvester is slightly crippled with the increase of the base excitation intensity.

本文提出了一种具有可调刚度的电磁双稳态能量收集器 (EBEH)，用于从流致振动 (FIV) 场景中收集流体动能。考虑涡激力、尾流振荡器效应、负线性刚度和混合激励，建立了磁-机-电耦合系统的数学模型。采用具有可调势垒高度的双稳态系统来增强涡激振动 (VIV) 的最先进的能量清除性能。通过CFD模拟对锁定风速范围内的VIV进行了初步验证。在孤立涡激振动 (VIV) 和混合激励下评估了基于 FIV 的 EBEH 的非线性能量传输能力和能量转换性能。仿真结果表明，具有较大负线性刚度的EBEH在较宽的入口速度范围内具有较高的能量转换效率和目标能量传递能力。汽缸涡激振动的大振幅、低频振动主要是由升力脉动引起的，而小振幅、高频的飞驰则是由阻力的垂直分量脉动引起的。不同流入速度下的升力/阻力系数的波动与圆柱钝体的 VIV 或驰振幅值直接相关。具体来说，频率 汽缸涡激振动的大振幅、低频振动主要是由升力脉动引起的，而小振幅、高频的飞驰则是由阻力的垂直分量脉动引起的。不同流入速度下的升力/阻力系数的波动与圆柱钝体的 VIV 或驰振幅值直接相关。具体来说，频率 汽缸涡激振动的大振幅、低频振动主要是由升力脉动引起的，而小振幅、高频的飞驰则是由阻力的垂直分量脉动引起的。不同流入速度下的升力/阻力系数的波动与圆柱钝体的 VIV 或驰振幅值直接相关。具体来说，频率f _D大约是频率f _L的两倍在较宽的流入速度范围内；在 1.0 m/s 到 20 m/s 的宽流入速度范围内，波动升力的幅度超过 2.0。当流入速度范围为 20 m/s 至 30 m/s 时，具有较小势垒高度的基于 FIV 的 EBEH 的非线性能量传输效率大于 60%。具有适当负刚度的 EBEH 的非线性能量传输能力优于其对应的立方刚度十倍以上。从 EBEH 获得的最大平均收集功率可以比立方刚度情况增加 900% 以上。无论负刚度变化如何，使 EBEH 输出功率最大化的最佳外部负载约为 50 Ω。此外，当涡激振动无法唤醒时，基础激励的干预导致相当大的混沌运动，包括在低流入速度下的非周期性井内和井间跳变。然而，双稳态能量采集器的非线性能量传输效率随着基极激发强度的增加而略有下降。