Effect of the vortical structures on the hydrodynamic performance of a pitching hydrofoil

IF 2.5 3区工程技术

Journal of Hydrodynamics Pub Date : 2024-06-14 DOI:10.1007/s42241-024-0030-x

Rui Yuan, Hui-yun Hao, Qin Wu, Yun-qing Liu, Biao Huang

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Abstract

The objective is to study the vortical structural behaviors of a transient pitching hydrofoil and their effects on the hydrodynamic performance. The pitching motion of the hydrofoil is set to pitch up with an almost constant rate from 5° to 15° and then back to 5°, with the Reynolds number 4.4×10⁵ and the frequency 2 Hz. The results show that the main coherent structures around the pitching hydrofoil include small-scale laminar separation bubble (LSB), large-scale second vortex (SV) and trailing edge vortex (TEV) which are all vortical. The relationship between the vortical structure and the lift is investigated with the finite-domain impulse theory. It indicates that the major part of the lift is contributed by the LSB, whereas the shedding and the formation of the SV and TEV cause the fluctuation of the lift. The proper orthogonal decomposition (POD) method is applied to capture the most energetic modes, revealing that the LSB mode occupies a large amount of energy in the flow field. The dynamic mode decomposition (DMD) method accurately extracts the dominant frequency and modal characteristics, with the first mode corresponding to the mean flow, the second mode corresponding to the LSB structure and the third and fourth modes corresponding to the vortex shedding.

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涡流结构对俯仰水翼流体力学性能的影响

目的是研究瞬态俯仰水翼的涡旋结构行为及其对水动力性能的影响。在雷诺数为 4.4×105 和频率为 2 Hz 的条件下，水翼的俯仰运动被设定为以几乎恒定的速率从 5° 俯仰到 15°，然后再回到 5°。结果表明，俯仰水翼周围的主要相干结构包括小尺度层流分离气泡（LSB）、大尺度第二漩涡（SV）和后缘漩涡（TEV），它们都是涡旋结构。利用有限域冲量理论研究了涡旋结构与升力之间的关系。结果表明，升力的主要部分由 LSB 贡献，而 SV 和 TEV 的脱落和形成则导致了升力的波动。应用适当的正交分解（POD）方法捕捉能量最大的模式，发现 LSB 模式在流场中占据了大量能量。动态模态分解（DMD）方法准确地提取了主导频率和模态特征，其中第一模态与平均流相对应，第二模态与 LSB 结构相对应，第三和第四模态与涡流脱落相对应。

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来源期刊

Journal of Hydrodynamics MECHANICS-

自引率

12.00%

发文量

2374

审稿时长

4.6 months

期刊介绍： Journal of Hydrodynamics is devoted to the publication of original theoretical, computational and experimental contributions to the all aspects of hydrodynamics. It covers advances in the naval architecture and ocean engineering, marine and ocean engineering, environmental engineering, water conservancy and hydropower engineering, energy exploration, chemical engineering, biological and biomedical engineering etc.