Abstract Two hydrofoils with a tandem spatial configuration can share the same flow window. The wake vortex interaction and blockage effect have noticeable impacts on the response of two hydrofoils for a semi-passive system. In this study, the responses of two oscillating hydrofoils with a tandem arrangement are examined using a numerical approach. The results indicate that the downstream hydrofoil has an inferior energy harvesting performance because it operates in the upstream hydrofoil wake. Several special cases were observed. As a result of a negative interaction in the wake vortices, (i) two hydrofoils were shown to have different heaving equilibrium positions and thus no longer share the flow window; and (ii) the downstream hydrofoil was demonstrated to have a larger heaving amplitude but a lower energy harvesting performance. At a very high oscillation frequency, the downstream hydrofoil tends to incur an irregular response owing to the intense vortex formation and shedding, as well as a constant interaction of the wake vortices. The downstream hydrofoil achieves an unexpectedly better energy harvesting performance due to a favorable interaction of the wake vortices. However, the entire system can’t achieve high efficiency due to the poor energy harvesting performance of the upstream hydrofoil. When two semi-passive oscillating hydrofoils have a tandem configuration, negative wake vortex interactions should be avoided instead of seeking a favorable interaction.

中文翻译：

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具有串联配置的两个半被动振荡水翼的行为

摘要 具有串联空间配置的两个水翼可以共享同一个流动窗口。尾涡相互作用和阻塞效应对半被动系统的两个水翼的响应有显着影响。在这项研究中，使用数值方法检查了两个串联排列的振荡水翼的响应。结果表明，下游水翼在上游水翼尾流中运行，因此能量收集性能较差。观察到几个特殊情况。由于尾流中的负相互作用，(i) 两个水翼显示出具有不同的垂荡平衡位置，因此不再共享流动窗口；(ii) 下游水翼被证明具有较大的起伏幅度但较低的能量收集性能。在非常高的振荡频率下，由于强烈的涡流形成和脱落，以及尾涡的持续相互作用，下游水翼往往会产生不规则的响应。由于尾涡的有利相互作用，下游水翼实现了出乎意料的更好的能量收集性能。然而，由于上游水翼的能量收集性能较差，整个系统无法实现高效率。当两个半被动振荡水翼具有串联配置时，应避免负尾涡相互作用，而不是寻求有利的相互作用。由于尾涡的有利相互作用，下游水翼实现了出乎意料的更好的能量收集性能。然而，由于上游水翼的能量收集性能较差，整个系统无法实现高效率。当两个半被动振荡水翼具有串联配置时，应避免负尾涡相互作用，而不是寻求有利的相互作用。由于尾涡的有利相互作用，下游水翼实现了出乎意料的更好的能量收集性能。然而，由于上游水翼的能量收集性能较差，整个系统无法实现高效率。当两个半被动振荡水翼具有串联配置时，应避免负尾涡相互作用，而不是寻求有利的相互作用。