Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
J R Soc Interface. 2013 May 8;10(84):20130099. doi: 10.1098/rsif.2013.0099. Print 2013 Jul 6.
Flight in animals is the result of aerodynamic forces generated as flight muscles drive the wings through air. Aerial performance is therefore limited by the efficiency with which momentum is imparted to the air, a property that can be measured using modern techniques. We measured the induced flow fields around six hawkmoth species flying tethered in a wind tunnel to assess span efficiency, ei, and from these measurements, determined the morphological and kinematic characters that predict efficient flight. The species were selected to represent a range in wingspan from 40 to 110 mm (2.75 times) and in mass from 0.2 to 1.5 g (7.5 times) but they were similar in their overall shape and their ecology. From high spatio-temporal resolution quantitative wake images, we extracted time-resolved downwash distributions behind the hawkmoths, calculating instantaneous values of ei throughout the wingbeat cycle as well as multi-wingbeat averages. Span efficiency correlated positively with normalized lift and negatively with advance ratio. Average span efficiencies for the moths ranged from 0.31 to 0.60 showing that the standard generic value of 0.83 used in previous studies of animal flight is not a suitable approximation of aerodynamic performance in insects.
动物飞行是飞行肌肉驱动翅膀穿过空气产生的空气动力的结果。因此，飞行性能受到将动量传递给空气的效率的限制，这一特性可以用现代技术来测量。我们测量了六种在风洞中被系绳飞行的天蛾的诱导流场，以评估展向效率 ei，并从这些测量中确定了预测高效飞行的形态和运动学特征。选择这些物种来代表翼展范围从 40 到 110 毫米（2.75 倍）和质量范围从 0.2 到 1.5 克（7.5 倍），但它们在整体形状和生态方面相似。从高时空分辨率定量尾迹图像中，我们提取了天蛾后面的时间分辨下洗分布，计算了整个翅膀拍打周期以及多翅膀拍打周期的瞬时 ei 值。展向效率与归一化升力呈正相关，与前进比呈负相关。这些天蛾的平均展向效率范围从 0.31 到 0.60，表明以前对动物飞行的研究中使用的标准通用值 0.83 不是昆虫空气动力学性能的合适近似值。
