Effects of variable damping on hydrokinetic energy conversion of a cylinder using wake-induced vibration

The Wake-Induced Vibration (WIV) energy converter can be used to harvest hydrokinetic energy from ocean currents. A variable damping scheme is proposed based on the idea that damping dynamically adjusts with the vibration velocity. Large damping is adopted to improve the energy conversion performance when the vibration velocity is high. Similarly, small damping is adopted to reduce the resistance of the cylinder when the vibration velocity is low. Meanwhile, since the nonlinear damping is too sensitive at higher vibration velocity, the segmental nonlinear damping model is also proposed. The research shows that (1) the variable damping model is more effective than the constant damping model to enhance the WIV response; (2) four interference regions are found according to the vortex interaction between upstream and downstream cylinders: Reattachment, Co-shedding, Wake interference, Isolated region; (3) In the Co-shedding region and Wake Interference region, the energy conversion performance of the linear variable damping is the highest. (4) the energy conversion performance of the nonlinear variable damping model is greater than that of other models in the Reattachment and Isolated Region.