An experimental study in a wind tunnel is presented to explore the wake of a floating wind turbine subjected to harmonic side-to-side and fore–aft motions under laminar inflow conditions. The wake recovery is analysed as a function of the frequency of motion $f_p$ , expressed by the rotor-based Strouhal number, $St = f_p D / U_{\infty }$ ( $D$ is the rotor diameter, $U_{\infty }$ the inflow wind speed). Our findings indicate that both directions of motion accelerate the transition to the far-wake compared with the fixed turbine. The experimental outcomes confirm the computational fluid dynamics results of Li et al. (J. Fluid Mech., vol. 934, 2022, p. A29) showing that sideways motions lead to faster wake recovery, especially for $St \in [0.2, 0.6]$ . Additionally, we find that fore–aft motions also lead to better recovery for $St \in [0.3, 0.9]$ . The recovery is closely linked to nonlinear spatiotemporal dynamics found in the shear layer region of the wake. For both directions of motion and $St \in [0.2, 0.55]$ , the noisy wake dynamics lock in to the frequency of the motion. In this synchronised-like state, sideways motions result in large coherent structures of meandering, and fore–aft movements induce coherent pulsing of the wake. For fore–aft motion and $St \in [0.55, 0.9]$ , the wake shows a more complex quasiperiodic dynamic, namely, a self-generated meandering mode emerges, which interacts nonlinearly with the excitation frequency $St$ , as evidenced by the occurrence of mixing components. The coherent structures grow nonlinearly, enhance wake mixing and accelerate the transition to the far-wake, which, once reached, exhibits universal behaviour.

中文翻译：

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浮动海上风力涡轮机后非线性动力学导致的增强恢复

一项风洞实验研究旨在探索层流流入条件下浮动风力涡轮机受到谐波左右和前后运动的尾流。尾流恢复被分析为运动频率的函数 $f_p$ ，由基于转子的斯特劳哈尔数表示， $St = f_p D / U_{\infty }$ （ $D$ 是转子直径， $U_{\infty}$ 流入风速）。我们的研究结果表明，与固定涡轮机相比，两个运动方向都加速了向远尾流的过渡。实验结果证实了Li的计算流体动力学结果等人。（J.流体机械。，卷。 934，2022 年，第 934 页。 A29）表明侧向运动会导致更快的尾流恢复，特别是对于 $St \in [0.2, 0.6]$ 。此外，我们发现前后运动也能带来更好的恢复 $St \in [0.3, 0.9]$ 。该恢复与尾流剪切层区域中发现的非线性时空动力学密切相关。对于两个运动方向和 $St \in [0.2, 0.55]$ ，噪声尾流动力​​学锁定运动频率。在这种类似同步的状态下，侧向运动会产生大的蜿蜒连贯结构，前后运动会引起尾流的连贯脉冲。对于前后运动和 $St \in [0.55, 0.9]$ ，尾流表现出更复杂的准周期动态，即出现自生曲流模式，它与激励频率非线性相互作用 $圣$ ，正如混合成分的出现所证明的那样。相干结构非线性增长，增强尾流混合并加速向远尾流的过渡，一旦达到远尾流，就会表现出普遍的行为。