Power and Efficiency of Two and Three Tandem Cylinders in Flow-Induced Oscillations: Effect of Large Passive Turbulence Stimulation and Adaptive Damping

Abstract The Marine Renewable Laboratory at the University of Michigan has introduced passive turbulence control (PTC) and adaptive damping to enhance flow induced oscillations with an objective to increase the power-to-volume ratio of the VIVACE Converter. A combination of two sizes of PTC and four values of damping, with two and three oscillators are used to improve the power and efficiency of the system. It is found that adding a third cylinder to the system with a small PTC greatly increases the power-to-volume ratio without increasing the amplitude ratio. The trend of power for three cylinders with small PTC increases continuously with the flow speed, whereas the power trend for two cylinders in tandem with small PTC at high flow speed reaches a plateau. Generally, adding large PTC to the cylinders greatly improves the power to volume ratio at all flow speeds, but it also increases the amplitude ratio, hence, increasing the risk of oscillators experiencing high stress and potential damage to oscillators and their frames. Three-cylinder systems with small PTC and two-cylinder systems with large PTC are found to harvest largest amount of power under two scenarios: The three cylinders with small PTC work best for limited spaces at high water speeds, such as observed in canals. The two cylinders with large PTC harvest larger amounts of power but require larger space due to high amplitude ratio A*. This setup is expected to work best in open spaces such as deep rivers or in the ocean.