飞行器的升力、阻力及升力与环量定理的起源
DERIVATION OF LIFT, DRAG AND THE KUTTA--JOUKOWSKI THEOREM FOR AIRCRAFTS 1)
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摘要: 本文介绍了空气动力学中几个基本概念与定律的起源。其中,升力与阻力分别是空气对物体作用力的两个方向上的分量,它们均是由空气与物体的相对运动而产生的,并与该运动速度的平方成正比。库塔儒可夫斯基升力环量定理给出了翼型升力与翼型绕流之间的关系,开启了20世纪早期各国对翼型性能的研究。同时,鉴于理想流体圆柱绕流无阻力的理论结果与实验观察存在的矛盾开始激发人们对黏性流体运动的研究兴趣,并由此诞生了纳维斯托克斯方程组。而后普朗特提出边界层概念,巧妙解决了局部流动与整体流动的关系问题。针对大展弦比直机翼,普朗特又提出了基于升力线假设的升力线模型,并根据翼型气动数据得到三维机翼的气动性能。Abstract: Several fundamental concepts and laws in aerodynamics are introduced and summarized in the article. Lift and drag are the two components of the air's force on the object respectively. They are caused by the relative motion of the object and the air, and proportional to the square of the speed of the motion. The Kutta-Joukowski theorem gives the relationship between the airfoil lift and the airfoil flow, and sparked the study of airfoil performance in the early 20th century. Furthermore, the contradiction between the calculation conclution of the inviscid flow around a cylinder and the experimental observations inspired the study of the viscous flow motion, therefore the Navier--Stokes equation was born. Then Prandt proposed the concept of boundary layer and skillfully solved the relationship between local flow and overall flow. For the wings with large aspect ratio, Prandt proposed a lift surface model based on the lift line assumption, which can obtain the aerodynamic performance of the wing based on the performance of the airfoil.