Abstract
Near trapping is a kind of strong hydrodynamic interaction phenomenon in a regular array under specific incident wave conditions, which causes the excitation force on the structures in the array to change suddenly. In this paper, based on linear potential flow theory, the effects of near trapping on the hydrodynamic interaction and wave-power extraction characteristics of linear periodic arrays composed of the oscillating float type wave energy converters are studied by using the higher-order boundary element method in a frequency domain. The parameters considered include the separation spacing, number of devices, and incident wave direction. It is found that the near trapping significantly reduces the overall wave-power extraction, especially for the cases with a large number of devices, and changes the trend of the power distribution. The occurrence of the near trapping phenomenon depends on the ratio of the separation spacing to the wavelength and the incident wave direction. The results highlight the effective layout of linear arrays under the influence of near trapping, which not only ensures the total production power, but also reduces the power difference among wave energy converters.
Highlights
The arrays of wave energy converters (WECs) are a necessary trend of wave energy utilization for commercial viability
Beyond the separation spacings inducing the near trapping, the interaction factor of the upstream absorber decreases with the spacing, while those of the middle and downstream absorbers increase in the spacing range from 0.5 L to 3.5 L and from 3.5 L to 6.0 L
For all the arrays studied, at the near trapping conditions, i.e., dimensionless spacing (D/L) = 0.5n (β = 0◦) and D/L = n (β = 90◦), the mean interaction factor significantly decreases to the trough, which further indicates that the near trapping phenomenon can reduce the total power of the array
Summary
The arrays of wave energy converters (WECs) are a necessary trend of wave energy utilization for commercial viability. Mcguinness and Thomas [3] considered the hydrodynamic optimization of the linear and circular arrays, and concluded that the incident wave direction has a great influence on the overall performance. Both Andres et al [4] and Göteman et al [5] analyzed the effect of number of WECs and the spacing between WECs under the various wave conditions. Stratigaki et al [6] set up the experiment array composed of up to 25 identical WECs, and studied the important influence of array effect on the power absorption and the wave field by considering the quantity, spacing, and incident wave conditions.
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