2
Aerodynamics
2.1 Development of Aerodynamics
Aerodynamics is the study of the law of air motion and force when there is
relative motion between the object and air, that is, when the object moves
in the air or the object does not move, but air moves around the object.
Traditional aerodynamics refers to the aerodynamics of aircraft, especially the
aerodynamics of ordinary aircraft. The component force acting on a moving
aircraft perpendicular to the direction of flight is known as the lift for the
aircraft, which makes the aircraft “hold” in the air. The component force
acting on an aircraft parallel to the direction of flight plays a resistance role
in the flight of an aircraft.
In the study of aerodynamics, the motion of an aircraft passing through
the air is often equivalent to the motion of an aircraft bypassing the aircraft
without moving air according to the principle of relative flight. The principle
of relative flight refers to the situation when an aircraft moves along a straight
line at a constant speed in static air. The relative motion law states that the
mutual forces between the aircraft and the air are equivalent to the situation
when the aircraft is fixed but the air flows over the aircraft with the same
speed in the opposite direction, as shown in Fig. 2.1.
The principle of relative flight, which is the basic principle of aerodynamics
experiment, provides convenience for aerodynamics research. In the experimental study, the aircraft model can be fixed, and the straight and uniform
airflow around the model can be manufactured manually, so as to observe the
flow phenomenon, measure the aerodynamic forces on the model, conduct
the experimental aerodynamic study, and make the airflow easier to achieve
© Science Press 2021
P. Liu, A General Theory of Fluid Mechanics,
https://doi.org/10.1007/978-981-33-6660-2_2
79
Aerodynamics
2.1 Development of Aerodynamics
Aerodynamics is the study of the law of air motion and force when there is
relative motion between the object and air, that is, when the object moves
in the air or the object does not move, but air moves around the object.
Traditional aerodynamics refers to the aerodynamics of aircraft, especially the
aerodynamics of ordinary aircraft. The component force acting on a moving
aircraft perpendicular to the direction of flight is known as the lift for the
aircraft, which makes the aircraft “hold” in the air. The component force
acting on an aircraft parallel to the direction of flight plays a resistance role
in the flight of an aircraft.
In the study of aerodynamics, the motion of an aircraft passing through
the air is often equivalent to the motion of an aircraft bypassing the aircraft
without moving air according to the principle of relative flight. The principle
of relative flight refers to the situation when an aircraft moves along a straight
line at a constant speed in static air. The relative motion law states that the
mutual forces between the aircraft and the air are equivalent to the situation
when the aircraft is fixed but the air flows over the aircraft with the same
speed in the opposite direction, as shown in Fig. 2.1.
The principle of relative flight, which is the basic principle of aerodynamics
experiment, provides convenience for aerodynamics research. In the experimental study, the aircraft model can be fixed, and the straight and uniform
airflow around the model can be manufactured manually, so as to observe the
flow phenomenon, measure the aerodynamic forces on the model, conduct
the experimental aerodynamic study, and make the airflow easier to achieve
© Science Press 2021
P. Liu, A General Theory of Fluid Mechanics,
https://doi.org/10.1007/978-981-33-6660-2_2
79