航空模型機翼升力原理及阻力設置
發(fā)布時間:2021-07-24 來源:http://jjdoor.com.cn/
一、機翼升力原理
1、 Wing lift principle
如果兩手各拿一張薄紙,使它們之間的距離大約4~6厘米。然后用嘴向這兩張紙中間吹氣,你會看到,這兩張紙不但沒有分開,反而相互靠近了,而且用吹出的氣體速度越大,兩張紙就越靠近。從這個現(xiàn)象可以看出,當兩紙中間有空氣流過時,壓強變小了,紙外壓強比紙內(nèi)大,內(nèi)外的壓強差就把兩紙往中間壓去。中間空氣流動的速度越快,紙內(nèi)外的壓強差也就越大。
If you hold a thin piece of paper in each hand, make the distance between them about 4 ~ 6cm. Then blow air between the two sheets of paper with your mouth. You will see that the two sheets of paper are not separated, but close to each other. Moreover, the greater the speed of the most blown gas, the closer the two sheets of paper are. It can be seen from this phenomenon that when air flows between the two papers, the pressure becomes smaller, the pressure outside the paper is greater than that inside the paper, and the pressure difference between the inside and outside presses the two papers to the middle. The faster the middle air flows, the greater the pressure difference inside and outside the paper.
飛機機翼地翼剖面又叫做翼型,一般翼型的前端圓鈍、后端尖銳,上表面拱起、下表面較平,呈魚側形。前端點叫做前緣,后端點叫做后緣,兩點之間的連線叫做翼弦。當氣流迎面流過機翼時,流線分布情況如圖2。原來是一股氣流,由于機翼地插入,被分成上下兩股。通過機翼后,在后緣又重合成一股。由于機翼上表面拱起,是上方的那股氣流的通道變窄。根據(jù)氣流的連續(xù)性原理和伯努利定理可以得知,機翼上方的壓強比機翼下方的壓強小,也就是說,機翼下表面受到向上的壓力比機翼上表面受到向下的壓力要大,這個壓力差就是機翼產(chǎn)生的升力。
The ground wing section of an aircraft wing is also called an airfoil. Generally, the front end of the airfoil is round and blunt, the rear end is sharp, the upper surface is arched, and the lower surface is flat, showing a fish side shape. The front point is called the leading edge, the rear point is called the trailing edge, and the line between the two points is called the chord. When the air flows head-on through the wing, the streamline distribution is shown in Figure 2. It turned out to be a stream of air, which was divided into upper and lower streams due to the insertion of the wing. After passing through the wing, it reconstitutes a strand at the trailing edge. Because the upper surface of the wing is arched, the channel of the air flow above is narrowed. According to the continuity principle of air flow and Bernoulli's theorem, the pressure above the wing is smaller than that below the wing, that is, the upward pressure on the lower surface of the wing is greater than the downward pressure on the upper surface of the wing. This pressure difference is the lift generated by the wing.
二、飛機機的翼阻力
2、 Wing resistance of aircraft
只要物體同空氣有相對運動,必然有空氣阻力作用在物體上。作用在模型飛機上的阻力主要有摩擦阻力、壓差阻力和誘導阻力。
As long as the object moves relative to the air, there must be air resistance acting on the object. The resistance acting on the model aircraft mainly includes friction resistance, differential pressure resistance and induced resistance.
摩擦阻力:當空氣流過機翼表面的時候,由于空氣的粘性作用,在空氣和機翼表面之間會產(chǎn)生摩擦阻力。如果機翼表面的邊界層是層流邊界層,空氣粘性所引起的摩擦阻力比較小,如果機翼表面的邊界層是紊流邊界層,空氣粘性所引起的摩擦阻力就比較大。
Friction resistance: when air flows through the wing surface, due to the viscous effect of air, friction resistance will be generated between the air and the wing surface. If the boundary layer on the wing surface is a laminar boundary layer, the friction resistance caused by air viscosity is relatively small. If the boundary layer on the wing surface is a turbulent boundary layer, the friction resistance caused by air viscosity is relatively large.
為了減少摩擦阻力,可以減少模型飛機同空氣的接觸面積,也可以把模型飛機表面做光滑些。但不是越光滑越好,因為表面太光滑,容易保持層流邊界層,而層流邊界層的氣流容易分離,會使壓差阻力大大增加。
In order to reduce the friction resistance, the contact area between the model aircraft and the air can be reduced, and the surface of the model aircraft can also be made smoother. However, the smoother the better, because the surface is too smooth, it is easy to maintain the laminar boundary layer, and the air flow in the laminar boundary layer is easy to separate, which will greatly increase the differential pressure resistance.
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