Adaptive harnessing damping in hydrokinetic energy conversion by two rough tandem-cylinders using flow-induced vibrations

Journal Article · 26 December 2019 · Renewable Energy

DOI: https://doi.org/10.1016/j.renene.2019.12.076 · OSTI ID:1799244

Sun, Hai  ^[1]; Bernitsas, Marinos M. ^[2]; Turkol, Mert ^[3]

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1. Harbin Engineering University (China); University of Michigan, Ann Arbor, MI (United States); OSTI
2. University of Michigan, Ann Arbor, MI (United States); Northville High School, Northville, MI (United States)
3. University of Michigan, Ann Arbor, MI (United States)

Alternating lift technology (ALT) harnesses hydrokinetic energy from currents and tides and is different from conventional steady lift technologies (turbines). ALT is still under development with an important research issue being the mitigation of wake effect on downstream cylinders in Flow Induced Oscillations (FIO) of multi-cylinder Current Energy Converters (CEC). Rather than adjust the configuration/parameters of the converter, a more direct and effective way is to actively adjust the harnessed power. In this paper, a hydrokinetic energy converter using FIO of two cylinders in tandem in one-degree-of-freedom oscillators, with nonlinear adaptive damping and linear spring stiffness, is tested experimentally. FIO include Vortex Induced Vibrations (VIV), galloping, and their coexistence. Introducing adaptive damping into the tandem cylinders overcomes the shielding effect, which previous research on two tandem cylinders has shown to reduce power output by the downstream cylinder. Shielding along with fixed damping result either in ceasing motion due to excessive damping, or in low harnessed energy due to insufficient damping. In this experimental study, damping-to-velocity rate, linear spring-stiffness, cylinder spacing, and flow-velocity are the parameters with Reynolds number 30,000 ≤ Re ≤ 120,000. Comparison to linear-oscillators in FIO shows that this nonlinear converter, with velocity-proportional damping coefficient, is more effective over the entire FIO range but especially in galloping, where both flow and cylinder speeds are higher. Experimental results for energy harvesting, efficiency and instantaneous energy of the converter are presented and discussed supported by amplitude and frequency response data. Here the results show that the nonlinear, adaptive, velocity-proportional damping coefficient is an effective way to increase the overall harnessed power and the power of downstream cylinder. The harnessed power in the VIV to galloping transition increases by up to 94%. The most significant improvement is in the galloping region, where the increase in harnessed power and efficiency is around 33%.

• Research Organization: University of Michigan, Ann Arbor, MI (United States); Vortex Hydro Energy, Inc., Ann Arbor, MI (United States)
• Sponsoring Organization: National Key Research and Development of China; National Natural Science Foundation of China; Natural Science Foundation of Heilongjiang Province; USDOE; USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: EE0006780
• OSTI ID: 1799244
• Journal Information: Renewable Energy, Journal Name: Renewable Energy Journal Issue: C Vol. 149; ISSN 0960-1481
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English