氣動性能對候鳥飛行陣型影響之探討

本研究採用理論空氣動力學來探討候鳥於不同飛行陣型下的效率。候鳥如加拿大雁在遷徙時通常會採取特定的陣型來減少牠門的飛行阻力。本研究將探討幾種不同的飛行陣型來驗證候鳥遷徙時的最佳化陣型。我們使用Prandtl古典升力線理論、Helmholtz渦流理論以及Kutta-Joukowski理論來預測作用在每隻候鳥上的下沖氣流與誘導阻力。所有的計算皆採用自行編寫的Fortran程式完成。本研究探討幾種不同飛行陣型如V形、圓形、方形、直線以及水平線。實驗結果顯示V形陣型最前端的鳥(領頭鳥)承受較單隻飛行時較大的阻力。而在V形陣型後部的鳥承受較單隻飛行時較小的阻力。其它陣型並無與V陣型相同的特性，因此通常不被候鳥所採用。

關鍵字

升力線理論；誘導阻力；下沖氣流；飛行陣型

並列摘要

The performances of different flight formations of migratory birds are investigated by theoretical aerodynamics. Migratory birds such as the Canada geese usually arrange in a special array to reduce their flight drag during migration. In this research several different flight arrays are investigated to verify the optimized arrangement of migratory birds. We use Prandtl classical lifting line theory, Helmholtz vortex line theory, and Kutta-Joukowski theory to estimate the downwash and the induced drag acted on each bird. All the calculations are performed by an in-house Fortran program. Several different flight formations such as the V-shape, circle, square, vertical line, and horizontal line are investigated. The results have shown that the apex (or the leading) bird of the V-shaped formation suffers more induced drag than a single bird. The birds at the tail locations of the V-shaped formation suffer less induced drag than a single bird. Other formations do not have the same properties as the V-shaped formation, and are usually not adopted by the migratory birds.