Geometrical Evaluation on the Viscous Effect of Point-Absorber Wave-Energy Converters

Chen, Zhong Fei; Zhou, Binzhen; Zhang, Liang; Zhang, Wan Chao; Wang, Shu Qi; Zang, Jun

doi:10.1007/s13344-018-0046-5

Cited by 21 publications

(14 citation statements)

References 14 publications

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“…The WEC is a truncated vertical cylinder, whose flat bottom is generally regarded as the bottom shape most affected by drag damping effects in the heave direction [7,20,30]. The results of induced drag influence in this paper should therefore be considered as higher than more realistic designs.…”

Section: Discussionmentioning

confidence: 99%

“…Although significant drag force was obtained, the shear forces were very small overall. Also Chen et al [7] conclude from heave decay tests that the viscous effects are the largest for a flat bottom. They also highlight the difference in flow pattern surrounding the WEC for the different body shapes and put forward viscous correction factors, which are deduced from the deviation of the WEC decay motion from potential theory.…”

Section: Introductionmentioning

confidence: 99%

“…Using fully nonlinear Reynolds Averaged Navier-Stokes (RANS) simulations with the volume of fluid (VOF) method for the air-water interface has emerged as the most common method of choice in CFD for wave energy applications [3]. Many studies of point-absorbing WECs (PAWECs) have been presented over the last few years, e.g., [4][5][6][7][8][9][10], which has already spurred some reviews of the nonlinear numerical approaches to WEC design [3,[11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Palm

Eskilsson

Bergdahl

et al. 2018

JMSE

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This paper analyses the nonlinear forces on a moored point-absorbing wave energy converter (WEC) in resonance at prototype scale (1:1) and at model scale (1:16). Three simulation types were used: Reynolds Averaged Navier-Stokes (RANS), Euler and the linear radiation-diffraction method (linear). Results show that when the wave steepness is doubled, the response reduction is: (i) 3% due to the nonlinear mooring response and the Froude-Krylov force; (ii) 1-4% due to viscous forces; and (iii) 18-19% due to induced drag and non-linear added mass and radiation forces. The effect of the induced drag is shown to be largely scale-independent. It is caused by local pressure variations due to vortex generation below the body, which reduce the total pressure force on the hull. Euler simulations are shown to be scale-independent and the scale effects of the WEC are limited by the purely viscous contribution (1-4%) for the two waves studied. We recommend that experimental model scale test campaigns of WECs should be accompanied by RANS simulations, and the analysis complemented by scale-independent Euler simulations to quantify the scale-dependent part of the nonlinear effects.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Palm

Eskilsson

Bergdahl

et al. 2018

JMSE

View full text Add to dashboard Cite

show abstract

“…In contrast, the radiation forces (especially the damping term) were significantly affected by viscous effects. Chen et al (2018b) showed that the viscous effect of added mass was much smaller than that of radiation damping. The experimental results of Tom (2013) showed that the viscous effect did not change obviously with the wave frequency.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the viscous correction of the hydrodynamic coefficients of the floater at the natural frequency can meet the calculation requirements. The viscous hydrodynamic coefficients can be obtained from the experiment (Chen et al, 2018a;Lee et al, 2018) or CFD simulation (Chen et al, 2018b) of the free decay test.…”

Section: Introductionmentioning

confidence: 99%

Motion Response and Energy Conversion Performance of a Heaving Point Absorber Wave Energy Converter

Zhou

Sun

et al. 2020

Front. Energy Res.

Self Cite

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The heaving wave energy converter (WEC) is one typical type of point absorber WECs with high energy conversion efficiency but significantly affected by the viscous effect. It is widely known that the bottom shape of such WECs plays an important role in influencing the viscosity, so a detailed qualitative investigation is essential. Here a numerical study is performed for the influence of bottom shape on motion response and energy conversion performance of a heaving WEC. The numerical model is developed based on the potential flow theory with a viscous correction in the frequency domain. Cylindrical WECs with flat, cone, and hemispherical bottoms and the same displacement are considered. WECs with larger diameter-to-draft ratios (DDRs) are found to experience a relatively smaller viscous effect and achieve effective energy conversion in a broader frequency range. With the same DDR, the flat bottom has the most considerable viscous effect, following by the cone bottom with conical angles 90°and the hemispherical bottom. When the DDR is relatively small, the hemispherical bottom had the best energy conversion performance. Similarly, when the DDR is relatively large, the energy conversion performance of the floater with a hemispherical bottom and a cone bottom with 90°is better, while that with the flat bottom is the worst.

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Analysis of the Hydrodynamic Performance of an Oyster Wave Energy Converter Using Star-CCM+

Zheng

Zhang

Zhou

et al. 2019

J. Marine. Sci. Appl.

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Geometrical Evaluation on the Viscous Effect of Point-Absorber Wave-Energy Converters

Cited by 21 publications

References 14 publications

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Motion Response and Energy Conversion Performance of a Heaving Point Absorber Wave Energy Converter

Analysis of the Hydrodynamic Performance of an Oyster Wave Energy Converter Using Star-CCM+

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