Hedrick Tyson L, Usherwood James R, Biewener Andrew A
Concord Field Station, Museum of Comparative Zoology, Harvard University, 100 Old Causeway Road, Bedford, MA 01730, USA.
J Exp Biol. 2004 Apr;207(Pt 10):1689-702. doi: 10.1242/jeb.00933.
We used a combination of high-speed 3-D kinematics and three-axis accelerometer recordings obtained from cockatiels flying in a low-turbulence wind tunnel to characterize the instantaneous accelerations and, by extension, the net aerodynamic forces produced throughout the wingbeat cycle across a broad range of flight speeds (1-13 m s(-1)). Our goals were to investigate the variation in instantaneous aerodynamic force production during the wingbeat cycle of birds flying across a range of steady speeds, testing two predictions regarding aerodynamic force generation in upstroke and the commonly held assumption that all of the kinetic energy imparted to the wings of a bird in flapping flight is recovered as useful aerodynamic work. We found that cockatiels produce only a limited amount of lift during upstroke (14% of downstroke lift) at slower flight speeds (1-3 m s(-1)). Upstroke lift at intermediate flight speeds (7-11 m s(-1)) was moderate, averaging 39% of downstroke lift. Instantaneous aerodynamic forces were greatest near mid-downstroke. At the end of each half-stroke, during wing turnaround, aerodynamic forces were minimal, but inertial forces created by wing motion were large. However, we found that the inertial power requirements of downstroke (minimum of 0.29+/-0.10 W at 7 m s(-1) and maximum of 0.56+/-0.13 W at 1 m s(-1)) were consistent with the assumption that nearly all wing kinetic energy in downstroke was applied to the production of aerodynamic forces and therefore should not be added separately to the overall power cost of flight. The inertial power requirements of upstroke (minimum of 0.16+/-0.04 W at 7 m s(-1) and maximum of 0.35+/-0.11 W at 1 m s(-1)) cannot be recovered in a similar manner, but their magnitude was such that the power requirements for the upstroke musculature (minimum of 54+/-13 W kg(-1) at 7 m s(-1) and maximum of 122+/-35 W at 1 m s(-1)) fall within the established range for cockatiel flight muscle (<185 W kg(-1)).
我们采用高速三维运动学和三轴加速度计记录相结合的方法，这些记录来自在低湍流风洞中飞行的鸡尾鹦鹉，以表征瞬时加速度，并由此推断在广泛飞行速度范围（1 - 13米/秒）内整个振翅周期产生的净空气动力。我们的目标是研究在一系列稳定速度下飞行的鸟类振翅周期内瞬时空气动力产生的变化，检验关于向上扑翼过程中空气动力产生的两个预测，以及一个普遍持有的假设，即在扑翼飞行中赋予鸟类翅膀的所有动能都能作为有用的空气动力功被回收。我们发现，在较慢飞行速度（1 - 3米/秒）时，鸡尾鹦鹉向上扑翼时产生的升力有限（仅为向下扑翼升力的14%）。中等飞行速度（7 - 11米/秒）时向上扑翼的升力适中，平均为向下扑翼升力的39%。瞬时空气动力在向下扑翼接近中点时最大。在每个半程冲程结束时，翅膀转向过程中，空气动力最小，但翅膀运动产生的惯性力很大。然而，我们发现向下扑翼的惯性功率需求（在7米/秒时最小为0.29±0.10瓦，在1米/秒时最大为0.56±0.13瓦）与以下假设一致，即向下扑翼时几乎所有翅膀动能都用于产生空气动力，因此不应单独加到飞行的总功率成本中。向上扑翼的惯性功率需求（在7米/秒时最小为0.16±0.04瓦，在1米/秒时最大为0.35±0.11瓦）无法以类似方式回收，但其大小使得向上扑翼肌肉组织的功率需求（在7米/秒时最小为54±13瓦/千克，在1米/秒时最大为122±35瓦）落在鸡尾鹦鹉飞行肌肉既定的范围内（<185瓦/千克）。
