Minimum shear wind strength required for dynamic soaring of albatrosses
Minimum shear wind strength required for dynamic soaring of albatrosses
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DOI：
10.1111/j.1474-919x.2004.00295.x
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发表时间：
2005-01-01
期刊：
影响因子：
2.1
通讯作者：
Sachs, G
中科院分区：
文献类型：
--
作者：
Sachs, G
能量从海面上方的切变风中的运动空气传递到鸟类被认为是动态翱翔的能量来源，目的是确定信天翁动态翱翔所需的最小切变风强度。重点是能量中性轨迹，这意味着来自移动空气的能量增益刚好足以补偿由于动态飙升周期的阻力而导致的能量损失。一个数学优化方法用于计算最小的剪切风能量中性轨迹，使用一个现实的飞行力学模型的信天翁翱翔。从而确定了动力滑翔所需的最小剪风强度。在信天翁出没的地区，最小切变风强度的大小经常存在或被超过，这一结果适用于两种控制情况，一种是自由选择的升力系数特性，另一种是恒定的升力系数特性。考虑了剪切流向鸟体传递能量的机理，结果表明，在上部曲线中有明显的能量增益，而在下部曲线中有明显的能量损失。因此，上面的曲线可以作为动力滑翔的特征飞行阶段，以实现能量增益。
The transfer of energy from the moving air in the shear wind above the sea surface to a bird is considered as an energy source for dynamic soaring, with the goal to determine the minimum shear wind strength required for the dynamic soaring of albatrosses. Focus is on energy-neutral trajectories, implying that the energy gain from the moving air is just sufficient to compensate for the energy loss due to drag for a dynamic soaring cycle. A mathematical optimization method is used for computing minimum shear wind energy-neutral trajectories, using a realistic flight mechanics model for the soaring of albatrosses. Thus, the minimum shear wind strength required for dynamic soaring is determined. The minimum shear wind strength is of a magnitude that often exists or is exceeded in areas in which albatrosses are found. This result holds for two control cases dealt with, one of which shows a freely selectable and the other a constant lift coefficient characteristic. The mechanism of energy transfer from the shear flow to the bird is considered, and it is shown that there is a significant energy gain in the upper curve and a loss in the lower curve. As a result, the upper curve can be qualified as the characteristic flight phase of dynamic soaring to achieve an energy gain.