Hydrokinetic Energy Harnessing Using Two Tandem Cylinders in Flow-Induced Oscillations: Effect of Adaptive Damping and Large Turbulence Stimulation

Abstract Large Passive Turbulence Control (PTC) and nonlinear adaptive damping are used together to improve the efficiency and power of the VIVACE converter. Small PTC and large PTC are applied to two cylinders in tandem. Linear damping is used on the upstream cylinder while adaptive damping is used on the downstream cylinder. In testing in the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan, the flow-induced oscillation (FIO) of the leading cylinder starts at a flow speed of 0.36 m/s. FIO initiates as linear resonance leading to vortex-induced vibration (VIV). Then, VIV and galloping coexist until the flow speed of 0.9 m/s before reaching fully developed galloping with no transition gap in FIO. The mechanical power of each cylinder is calculated based on experimental measurements. The combined mechanical power of the two cylinders increases quadratically with the flow speed. This redesigned PTC, along with adaptive damping, modifies the efficiency curve to be maximum over the range of reduced velocity 5 < U* < 8, regardless of stiffness and damping. This extended speed range of improved efficiency allows the converter to work well in real environments where the water flow may have nonuniform and time-varying speed.