Three-dimensional simulation for fast forward flight of a calliope hummingbird

We present a computational study of flapping-wing aerodynamics of a calliope hummingbird (Selasphorus calliope) during fast forward flight. Three-dimensional wing kinematics were incorporated into the model by extracting time-dependent wing position from high-speed videos of the bird flying in a wind tunnel at 8.3 m s−1. The advance ratio, i.e. the ratio between flight speed and average wingtip speed, is around one. An immersed-boundary method was used to simulate flow around the wings and bird body. The result shows that both downstroke and upstroke in a wingbeat cycle produce significant thrust for the bird to overcome drag on the body, and such thrust production comes at price of negative lift induced during upstroke. This feature might be shared with bats, while being distinct from insects and other birds, including closely related swifts.

本研究针对星蜂鸟（Selasphorus calliope）在快速前飞过程中的扑翼空气动力学特性开展计算研究。研究通过从风洞内以8.3 m·s⁻¹风速飞行的该鸟类的高速摄像序列中提取随时间变化的翼位置，将三维翼运动学参数整合至模型中。前进比（advance ratio），即飞行速度与翼尖平均速度的比值，约为1。本研究采用浸入边界法（immersed-boundary method）对翼与鸟体周围的流场进行数值模拟。结果显示，振翅周期内的下挥冲程与上挥冲程均可为鸟类提供用于克服体阻力的显著推力，而此类推力的产生需以上挥冲程中诱导产生的负升力为代价。这一特征或与蝙蝠共有，但与昆虫及包括亲缘关系较近的雨燕在内的其他鸟类存在显著差异。