wing tip vortex

…to achieve maximum speed, an aircraft should fly at the angle of attack that minimizes the drag coefficient, and to burn less fuel and fly longer distances, an aircraft should fly at the angle of attack that maximizes the lift-to-drag ratio.
[Wings and aspect ratio]
At the tip of the wing, the air below turns around to the upper surface where the pressure is lower, forming a vortex (called a wing tip vortex or a trailing vortex) (Figure 3), and the airflow passing over the wing is guided by this wing tip vortex and flows slightly downward. The smaller the aspect ratio of the wing, the stronger the influence of the wing tip vortex is, and the more downward the airflow becomes, which is why a larger angle of attack is required to generate the same lift as mentioned above.

*Some of the terminology that mentions "wing tip vortex" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…飛行機は，最高速度を出すには抗力係数が最小となる迎え角で，また燃料消費を減らして長距離を飛ぶには揚抗比が最大となる迎え角で飛ぶのがよい。
［翼とアスペクト比］
　翼端では下面の空気が圧力の低い上面へと回り込むので渦(この渦を翼端渦wing tip vortex，または後引き渦trailing vortexという)ができ(図3)，この翼端渦に誘導されて翼を通過する気流はやや下を向く。アスペクト比の小さい翼ほど翼端渦の影響が強く気流が下向きになり，前記の同じ揚力を出すのに大きな迎え角が必要となるのはこのためである。…

※「wing tip vortex」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報