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Ocean Engineering

# The VIVACE Converter: Model Tests at High Damping and Reynolds Number Around $105$

[+] Author and Article Information
Michael M. Bernitsas, Y. Ben-Simon, Kamaldev Raghavan, E. M. Garcia

Department of Naval Architecture and Marine Engineering, University of Michigan, 2600 Draper Road, Ann Arbor, MI 48109-2145

J. Offshore Mech. Arct. Eng 131(1), 011102 (Dec 11, 2008) (12 pages) doi:10.1115/1.2979796 History: Received July 03, 2006; Revised December 26, 2007; Published December 11, 2008

## Abstract

The vortex induced vibrations for aquatic clean energy (VIVACE) converter is a new concept to generate clean and renewable energy from fluid flows such as those abundant in oceans, rivers, or other water resources. The underlying concepts for design, scaling, and operation of VIVACE were introduced in Bernitsas, 2008, “VIVACE (Vortex Induced Vibration Aquatic Clean Energy): A New Concept in Generation of Clean and Renewable Energy From Fluid Flow  ,” ASME J. Offshore Mech. Arct. Eng., 130(4), p. 041101. In its simplest form, a VIVACE modulo consists of a single rigid cylinder mounted on elastic supports and connected to a power takeoff (PTO) system. The cylinder is placed in a steady unidirectional current and excited in vortex induced vibration (VIV). In this paper, the VIVACE modulo was tested in the Low Turbulence Free-Surface Water Channel of the University of Michigan to demonstrate the concept, generate electricity, measure the power out, and calculate basic benchmarking measures such as energy density. The tests performed were tailored to the particulars of the VIVACE modulo, which dictate that the cylinder operate in VIV under high damping and as high a Reynolds number as possible. At the same time, a broad range of synchronization is required to make VIVACE effective in energy generation in a realistic environment. Due to these requirements, VIV tests have not been performed before in the subspace applicable to the operation of the VIVACE modulo. In the process of extracting fluid kinetic energy and converting it to electricity in the laboratory, for a given set of cylinder-springs-transmission-generator, only the damping used for harnessing electricity was optimized. Even at this early stage of development, for the tested VIVACE modulo, the maximum peak power achieved was $Ppeak=0.308×12ρDLL$. The corresponding integrated power in that particular test was $PVIVACE=0.22×12ρU3DL$ with theoretical upper limit based on measurements of $PUL–VIVACE=0.3663$. Such power was achieved at velocity $U=0.840m∕s=1.63Kn$.

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## Figures

Figure 1

Simple schematic of a VIVACE modulo with coordinate system

Figure 2

VIVACE Model III in the low turbulence free-surface water channel

Figure 3

Experimental results on the effect of free-surface on the amplitude of oscillation

Figure 4

Separately excited generator used for the mathematical model

Figure 5

VIVACE with a two-gear transmission system

Figure 6

Schematic of a two-shaft transmission system

Figure 7

Typical recorded time histories of free decay oscillation in water for VIVACE Model III with gear disconnected

Figure 8

Free decay damping test results in water: comparison between VIVACE Model III with gear disconnected and Sumer’s compiled data (36)

Figure 9

Free decay damping test in water for VIVACE Model III with disconnected transmission

Figure 10

Free decay damping test in water for VIVACE Model III with connected transmission but disconnected generator

Figure 11

Free decay damping test in water for VIVACE Model III with connected transmission, generator, and RL=55Ω.

Figure 12

Time histories of measured cylinder displacement, potential, and power; and calculated cylinder velocity

Figure 13

Comparison of measured harnessed power to the power calculated using Eq. 47

Figure 14

Normalized amplitude versus water velocity for different RL

Figure 15

Generated power versus water velocity for different RL

Figure 16

Peak efficiency versus water velocity for different RL

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