Mechanism of alula-induced oblique flow in sustaining high lift on wings

WANG Wenchang; QIN Suyang; MOU Yicheng; XIANG Yang; LIU Hong

doi:10.7638/kqdlxxb-2024.0093

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Mechanism of alula-induced oblique flow in sustaining high lift on wings

更新时间：2026-05-28

- Mechanism of alula-induced oblique flow in sustaining high lift on wings
- Vol. 43, Issue 2, Pages: 27-39(2025)
- 作者机构：
  
  上海交通大学航空航天学院吴镇远空气动力学研究中心,上海,200240
- 作者简介：
- 基金信息：
- DOI：10.7638/kqdlxxb-2024.0093
  CLC： V211.7
- Published：2025
- 稿件说明：
移动端阅览
王文昶, 秦苏洋, 牟奕赪, 等. 小翼羽诱导斜向流动维持机翼高升力机制[J]. 空气动力学学报, 2025, 43(2): 27−39.

WANG Wenchang, QIN Suyang, MOU Yicheng, et al. Mechanism of alula-induced oblique flow in sustaining high lift on wings[J]. 2025, 43(2): 27-39.
王文昶, 秦苏洋, 牟奕赪, 等. 小翼羽诱导斜向流动维持机翼高升力机制[J]. 空气动力学学报, 2025, 43(2): 27−39. DOI： 10.7638/kqdlxxb-2024.0093

WANG Wenchang, QIN Suyang, MOU Yicheng, et al. Mechanism of alula-induced oblique flow in sustaining high lift on wings[J]. 2025, 43(2): 27-39. DOI： 10.7638/kqdlxxb-2024.0093.

摘要

小翼羽作为鸟类抑制流动分离和维持高升力的主要结构，其气动控制效果已被广泛验证，但目前仍缺乏小翼羽对大展弦比高升力机翼气动性能的影响规律及作用机制的相关研究。通过风洞实验结合气动力测量和体式粒子图像测速技术，探究小翼羽对机翼升力特性及上表面流场结构的影响。结果表明：小翼羽可在较宽的攻角范围内维持机翼高升力，但会使最大升力减小；高升力的维持主要源于小翼羽对分离流的控制作用，小翼羽诱导产生的斜向流动不仅可以为机翼上表面低速气流注入能量，还可与翼尖涡混合，增强其下洗作用；在部分截面，机翼上表面的气流在前缘受增强的翼尖涡影响，在靠近尾缘处受斜向流动影响，最终形成“二次加速”的流场结构；通过改变小翼羽的展向位置，发现机翼中段的小翼羽诱导的斜向流动强度最高，具备最佳的分离流控制效果。本文研究对无人机、微型飞行器等低雷诺数飞行器的增升设计具有指导意义。

Abstract

As a primary bird structure for suppressing flow separation and maintaining high lift

alula has been widely recognized for its control effects. However

the influence of alula on aerodynamic performance and the underlying mechanisms for high-lift wings with large aspect ratios remain underexplored. This study investigates the impact of alula on the lift characteristics and upper-surface flow field structures of wings using aerodynamic force measurements and stereo particle image velocimetry in a wind tunnel. The results show that alula can maintain high lift over a broad range of angles of attack although it reduces the maximum lift coefficient. The maintenance of high lift is primarily attributed to the control of separated flows by the alula. The oblique flow induced by the alula injects energy into the low-speed flow on the wing's upper surface and interacts with the wingtip vortex to enhance its downwash effect. At certain cross-sections

the flow on the wing's upper surface is influenced by the enhanced wingtip vortex near the leading edge and by the oblique flow near the trailing edge

ultimately forming a "reacceleration" flow structure. By altering the spanwise position of the alula

it is found that the alula at the mid-span of the wing induces the strongest oblique flow and achieves the best separation flow control effect. This study provides guidance for the lift-enhancement design of low Reynolds number aircraft

such as unmanned aerial vehicles and micro air vehicles.

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references

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