Abstract The paper presents a wave basin experiment of a direct-driven point-absorber wave energy converter moving in six degrees of freedom. The goal of the work is to study the dynamics and energy absorption of the wave energy converter, and to verify under which conditions numerical models restricted to heave can capture the behaviour of a point-absorber moving in six degrees of freedom. Several regular and irregular long-crested waves and different damping values of the power take-off system have been tested. We collected data in terms of power output, device motion in six degrees of freedom and wave elevation at different points of the wave basin. A single-body numerical model in the frequency domain and a two-body model in the time domain are used in the study. Motion instabilities due to parametric resonance observed during the experiments are discussed and analysis of the buoy motion in terms of the Mathieu instability is also presented. Our results show that the simplified models can reproduce the body dynamics of the studied converter as long as the transverse non-linear instabilities are not excited, which typically is the case in irregular waves. The performance of the more complex time domain model is able to reproduce both the buoy and PTO dynamics, while the simpler frequency domain model can only reproduce the PTO dynamics for specific cases. Finally, we show that the two-body dynamics of the studied wave energy converter affects the power absorption significantly, and that common assumptions in the numerical models, such as stiff mooring line or that the float moves only in heave, may lead to incorrect predictions for certain sea states.

中文翻译：

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通过简化的数值模型捕捉点吸收器 WEC 的实验行为

摘要 本文介绍了一种直驱式点吸收式波浪能转换器在六自由度上运动的波盆实验。这项工作的目标是研究波浪能转换器的动力学和能量吸收，并验证在哪些条件下仅限于升沉的数值模型可以捕捉在六个自由度上移动的点吸收器的行为。已经测试了几种规则和不规则的长波峰以及取力器系统的不同阻尼值。我们收集了功率输出、六个自由度的设备运动和波浪盆地不同点的波浪高度方面的数据。研究中使用频域中的单体数值模型和时域中的双体模型。讨论了由于在实验中观察到的参数共振引起的运动不稳定性，还介绍了根据 Mathieu 不稳定性对浮标运动的分析。我们的结果表明，只要横向非线性不稳定性不被激发，简化模型就可以再现所研究转换器的体动力学，这通常是不规则波的情况。更复杂的时域模型的性能能够再现浮标和取力器动力学，而更简单的频域模型只能再现特定情况下的取力器动力学。最后，我们表明所研究的波浪能转换器的双体动力学显着影响功率吸收，并且数值模型中的常见假设，例如刚性系泊绳或浮子仅在升沉时移动，