Hydrokinetic Power Conversion Using Vortex-Induced Oscillation with Cubic Restoring Force

Mengyu Li, Christopher Bernitsas, Guo Jing and Sun Hai
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Mengyu Li: College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001, China
Christopher Bernitsas: Marine Renewable Energy Laboratory, Department of Naval Architecture & Marine Engineering, University of Michigan, 2600 Draper Road, Ann Arbor, MI 48109-2145, USA
Guo Jing: Mathematical Sciences Department, Worcester Polytechnic Institute, Worcester, MA 01609, USA
Sun Hai: College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001, China

Energies, 2020, vol. 13, issue 12, 1-18

Abstract: A cubic-spring restoring function with high-deformation stiffening is introduced to passively improve the harnessed marine hydrokinetic power by using flow-induced oscillations/vibrations (FIO/V) of a cylinder. In these FIO/V experiments, a smooth, rigid, single-cylinder on elastic end-supports is tested at Reynolds numbers ranging from 24,000 < Re < 120,000. The parameters of the tested current energy converter (CEC) are cubic stiffness and linear damping. Using the second generation of digital virtual spring-damping (Vck) controller developed by the Marine Renewable Energy Laboratory (MRELab), the cubic modeling of the oscillator stiffness is tested. Experimental results show the influence of the parameter variation on the amplitude, frequency, energy conversion, energy efficiency, and power of the converter. All experiments are conducted in the low turbulence-free surface water (LTFSW) channel of the MRELab of the University of Michigan. The main conclusions are: (1) The nonlinearity in the cubic oscillator is an effective way to extend the vortex-induced vibration (VIV) upper branch, which results in higher harnessing power and efficiency compared to the linear stiffness cylinder converter. (2) Compared to the linear converter, the overall power increase is substantial. The nonlinear power optimum, occurring at the end of the VIV upper branch, is 63% higher than its linear counterpart. (3) The cubic stiffness converter with low harnessing damping achieves consistently good performance in all the VIV regions because of the hardening restoring force, especially at higher flow velocity.

Keywords: hydrokinetic energy; alternating lift technologies; cubic spring-stiffness; vortex-induced vibrations (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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