Abstract The hydrodynamic characteristics of a novel twin-protuberance hydrofoil design mimicking the two prominent tubercles present on a humpback whale flipper are investigated. The foil has NACA 634-021 section with a span/chord ratio of 2, having twin leading-edge protuberances- each of amplitude 10% of the chord length. A characteristic feature of this foil is its capability to restrict the separation zone between the chordwise vortices shed from the two humps at high angles of attack (>20 deg). A detailed comparison study based on experiments and CFD investigations using a transition model is presented for the twin-protuberance hydrofoil with a NACA 634-021 base foil and a foil with one protuberance of similar configuration. The general observation is a reduced pre-stall lift coefficient and maximum lift for the modified foils along with a higher post-stall lift coefficient compared to the base foil. The influence of Reynolds number and protuberance amplitude and spacing on the hydrodynamic performance is also investigated. The results indicate that such modifications can be used effectively for flow control at high angles of attack and suitably optimized for specific marine applications.

中文翻译：

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仿生双突起水翼设计

摘要 研究了模仿座头鲸鳍状肢上存在的两个突出结节的新型双突起水翼设计的流体动力学特性。翼片具有 NACA 634-021 截面，跨度/弦比为 2，具有两个前缘突起 - 每个幅度为弦长的 10%。这种箔的一个特征是它能够限制从两个驼峰以大迎角（> 20 度）脱落的弦向涡流之间的分离区。针对具有 NACA 634-021 基箔的双突起水翼和具有类似配置的一个突起的水翼，基于实验和 CFD 研究使用过渡模型进行了详细的比较研究。一般观察到，与基础翼相比，改进后的翼降低了失速前升力系数和最大升力，以及更高的失速后升力系数。还研究了雷诺数和突起幅度和间距对水动力性能的影响。结果表明，这种修改可以有效地用于大迎角下的流量控制，并针对特定的海洋应用进行适当优化。