What is the force on the aircraft during flight?

First of all, as you said, when a low-velocity, non-compressible ideal fluid flows around the airfoil, both the upper and lower surfaces of the airfoil generate pressure. However, in general, when conducting aerodynamic studies, whether it is experimental or theoretical research, the pressure coefficient cp is used instead of the actual pressure value. Pressure coefficient cp=( p -p ) ( p is the measured pressure, p is the flow pressure from a distance, flow pressure from a distance, the pressure p will never be negative, but cp can be positive or negative.)

In other words, p is chosen as the basis for the calculation. If p >p then cp>0;As p p , so cp>0. On the pressure distribution diagram, the upper surface arrows of the airfoil are departing from the airfoil, while the lower surface arrows are pointing towards the airfoil.

So, it is not correct to interpret cp<0 as suction because it is a dimensionless coefficient. <>

Force: total aerodynamics, gravity, thrust; Moment: aerodynamic moment, thrust eccentric moment.

Take missiles as an example, the plane should be about the same, I haven't studied it, I dare not say absolutely. In level flight, the lift can be balanced by gravity, where the lift is generated by the wing surface, and to generate the lift, it is generally necessary to have an angle of attack.

That is, the relative velocity of the missile.

There is a declination angle (i.e., the head of the head), which creates lift (here we will only focus on the wings). In the same way, if you want to have a ballistic upward, you also need to have a positive angle of attack. For normal missiles (the wing surface is in front and the rudder surface is in the rear), a negative rudder inclination angle is required to produce a positive angle of attack, and the principle of this is that the torque needs to be balanced.

Turning, for aircraft, generally use BTT, that is, roll turning, because the rudder surface is too small relative to the wing surface, if you rely directly on the rudder to provide lateral force, the turn will be next year. BTT refers to rolling first and then turning, that is, using the mechanism of different lift of the wing surface after rolling. <>

Aircraft Zhilv is subjected to a variety of loads during flight, including:

Gravitational load: The force exerted by the aircraft's own weight on the fuselage, the so-called gravitational force.

Lift Load: Due to the lift generated by the wings, the aircraft generates an upward force perpendicular to the direction of the fuselage.

Thrust load: The force exerted on the fuselage by the thrust generated by the engine.

Resistance load: Because the aircraft moves in the air, it will produce Hu Mengjing drag, which makes the aircraft produce a force opposite to the direction of motion.

Inertial load: Due to the acceleration generated by the aircraft during flight, some inertial forces occur inside the aircraft, such as acceleration during take-off and landing.

Wind load: An external load that occurs due to the fact that the aircraft is affected by air currents during flight.

These loads have an impact on the structure and performance of the aircraft, and designers need to consider these factors to ensure the safety and performance of the aircraft.

1. Differential pressure resistance. When the relative airflow flows through the wing, the airflow at the leading edge of the wing is blocked, the flow velocity slows down, and the pressure increases; The airflow at the trailing edge of the wing separates, forming a vortex zone and the pressure decreases. In this way, a pressure difference between the front and rear of the wing creates resistance. This resistance is called differential pressure resistance.

2. Friction resistance. Frictional resistance, or surface resistance, is a type of resistance that occurs when the fluid around an object flows along the surface contour of the object in the opposite direction of the object's motion when moving forward. Frictional resistance has a great relationship with airplanes, racing cars, speedboats and other objects that are streamlined and in motion (often accounting for more than 70% of the total resistance), and also has a certain impact on the speed of swimming.

3. Induce resistance. In addition to frictional resistance and differential pressure resistance, there is also an additional drag force generated on the wing due to the generation of lift. This additional drag induced due to the generation of lift is called induced drag.

It can be said that induced resistance is a kind of "return and dismantling" to pay for the generation of lift.

4. Interference resistance. Practice has shown that the sum of the drag generated by the various parts of the aircraft, such as the wings, the fume and the tail, when placed alone in the airflow, is not equal to the drag generated by the whole, but is often less than the drag generated when they are put together as a whole. The so-called "interference drag" is an additional drag between the various parts of the aircraft due to the air flow interfering with each other.

In the process of aircraft lifting, the drag force is the gravity of the whole aircraft, the elastic force of the air on the aircraft, that is, the air resistance, and the friction between the aircraft and the air;

In the process of smooth flight of the aircraft, the drag force is air resistance and friction;

In the final approach stage, the drag force is air resistance, friction and lift (passenger aircraft generally approach at a positive elevation angle).

They are: gravity, lift, drag, thrust. An airplane is a giant machine that flies in the sky and weighs between a few tons and hundreds of tons, from which gravity is generated.

In order to overcome its weight, it is necessary to provide a force that is collinear opposite to gravity to bring the aircraft to relative equilibrium in the vertical direction, which is the lift force.

There will be various resistances in the air, which can be divided into friction resistance, differential pressure resistance, induced resistance and interference resistance according to the causes of resistance.

The coarse force of the force exerted by the air flow on the inner and outer surfaces of the engine is the driving force generated by the engine. The gas gives the engine a reaction force in the direction of flight, which is thrust.

Drag is the component of the aerodynamic net force of an aircraft in a plane of longitudinal symmetry, parallel to the direction of flight. To maintain continuous flight, the aircraft's power plant must generate sufficient thrust to overcome drag.