Why do planes fly, why do planes fly?

Because it's the same as a bird that has wings.

1. Flight Principle When the aircraft moves in the air, it relies on the wings to generate lift to lift the aircraft off the land. How does wing lift occur? This starts with the fundamentals of airflow.

In daily life, when there is wind, we will feel that there is air flowing through the body, which is particularly cool; When there is no wind, you will experience the same experience when riding a bicycle, which is the result of the relative airflow. When the river is surging and flows through a narrow place, the water flow speed is fast; When passing over a wide river, the flow of water slows down and the flow rate is slower. The same is true of air, when it flows through a pipe of different thicknesses, because the air flows continuously and steadily in the pipe, under the condition that the air density remains the same, how much flows in from the thick end of the pipe will flow out from the thin end per unit time.

Therefore, when the air passes through a thin duct, it must be accelerated to ensure that the flow rate is the same. From this, we derive the characteristics of the flowing air: the flow tube is thin and the flow rate is fast; The flow tube is rough and the flow rate is slow.

This is the principle of airflow continuity. It has been proven that a change in the speed of air flow can also cause a change in pressure. When the fluid flows steadily through a pipe, the pressure is low where the flow rate is fast.

There is a lot of pressure where the flow rate is slow. When the aircraft moves forward, the air flows to the leading edge of the wing, which is divided into upper and lower strands, and flows through the streamlines expressed on the wings, which are affected by the bulge, so that the streamlines converge and become denser, and the flow tubes (which regard the two adjacent streamlines as the walls of the tubes) become thinner; The streamline flowing through the lower surface is also affected by the convexity, but the convex degree of the lower surface is significantly smaller than that of the upper surface, so the streamline is looser than the upper surface, and the flow tube is thicker. Due to the thinner flow tube on the upper surface of the wing, the flow velocity is increased and the pressure is less, while the lower surface flow tube is thicker, the flow rate is slow, and the pressure is greater.

As a result, there is a pressure difference between the upper and lower surfaces of the wing. The sum of this pressure difference acting on each section of the wing is the lift of the wing (see figure). Its direction is perpendicular to the direction of the relative airflow; Its size is mainly affected by factors such as flight speed, angle of attack (the angle between the wing chord and the direction of the relative airflow), air density, wing slice shape, and wing area.

Of course, the fuselage, horizontal tail and other parts of the aircraft can also generate part of the lift, but the wing lift is the main source of lift for the aircraft. The reason why the aircraft can take off and land is mainly achieved by changing the magnitude of its lift. This is the secret of the fact that airplanes can lift off from land and fly in the air.

The side profile of the wing is a shape in which the upper edge is arched upwards and the lower edge is basically straight. Therefore, the air flow blowing through the upper and lower surfaces of the wing and from the front end of the wing to the rear end at the same time will pass through the upper edge faster than the lower edge (because the upper edge has a large arc and a longer arc length, which means that the distance is longer).

According to the Bernoulli equation of physics, the same fluid flowing through a certain surface has less pressure on the surface at a faster speed. Therefore, it is concluded that the atmospheric pressure on the upper surface of the wing is smaller than that on the lower surface, so that the lift force is generated, and the lift force reaches a certain level, and the aircraft can lift off the ground.

There's a formula that I don't know if you've ever seen: l cl*1 2* *v*v*s.

Its significance is that the lift of an aircraft is the product of the following five quantities:

1.Lift coefficient cl

That c represents the coefficient, l is the corner code, I don't have a character tool can't type), its value is related to many fine variables such as the windward angle of the aircraft, generally in a few tenths, the details are not very affectionate: (

2.Half.

It's the density of the atmosphere

The environment in which the aircraft is located, which can be high altitude or low altitude).

4.The square of the airplane's velocity relative to the surrounding atmosphere.

v*v (no corner code can not be typed, can only be expressed like this).

5.Wing area.

This formula is only suitable for relatively slow flights, just like the common flight of large and small passenger aircraft, other aircraft (as long as the wings) can be used when the speed does not exceed Mach 1, but the high speed flight of Mach 2 or 3 like a fighter is not good, if the speed is too large, the air on the surface of the wing will become viscous, to take into account the Reynolds number, there is another formula at that time, it is very complicated, I don't understand. ：）

Originally, humans wanted to be able to fly freely in the air like birds. Later, after repeated practice, the airplane was invented. And the plane can fly because of its wings and engines.

When the airplane is moving, the air above the wing is fast, and the air under the wing is slow, so that an upward lift is generated, and the plane will fly smoothly into the sky. In addition, the engine in the aircraft is connected to the propeller, and the propeller rotates to drive the airflow, and the aircraft can fly in the sky for a long time. (100,000 Why Nets for Elementary School Students) Why do airplanes fly?

Why do airplanes fly? Despite the cooperation of various departments, the main thing is that the aircraft has a pair of wings with a special profile shape. Wing profiles are also known as airfoils.

A typical airfoil is convex at the top and flat at the bottom, and is often referred to as streamlined. According to the continuity of the fluid and Bernoulli's theorem, the air flow through the upper surface is squeezed compared to the air far ahead, and the flow velocity accelerates and the pressure decreases, and even suction (negative pressure) is formed, and the flow velocity of the air flowing through the lower surface slows down. As a result, a pressure difference is formed between the upper and lower wing surfaces.

This pressure difference is aerodynamic. According to the law of force decomposition, it is broken down along the direction of flight into upward lift and backward resistance. The drag is overcome by the thrust provided by the engine.

The lift is just enough to overcome its own gravity and lift the aircraft into the air. That's why airplanes fly.

The wing of the aircraft is designed, when the aircraft is moving forward on the ground, the wings will have a downward pressure on the air, according to the interaction of forces, the air will give the aircraft an upward lift, when this lift reaches a certain level, the aircraft will be held up.

There is an aerodynamic principle here, the propeller of the aircraft will produce an updraft, and the wings can fly using this air flow, and the principle is roughly the same as that of steel ** floating on the water.

He can't fly, what kind of plane is he called?