Aerodynamics is a field of knowledge that studies the movement of air flows and their effects on solid bodies. It is a subsection of hydro- and gas dynamics. Research in this area dates back to ancient times, to the time of the invention of arrows and planning spears, which made it possible to send a projectile farther and more accurately at a target. However, the potential of aerodynamics was fully revealed with the invention of heavier-than-air vehicles capable of flying or gliding over considerable distances.
Since ancient times
The discovery of the laws of aerodynamics in the 20th century contributed to a fantastic leap in many areas of science and technology, especially in the transport sector. Based on its achievements, modern aircraft have been created, which made it possible to make virtually any corner of the planet Earth accessible to the public.
The first mention of an attempt to conquer the sky is found in the Greek myth of Icarus and Daedalus. Father and son built bird-like wings. This indicates that thousands of years ago people thought about the possibility of getting off the ground.
Another surgeinterest in the construction of aircraft arose during the Renaissance. Passionate researcher Leonardo da Vinci devoted a lot of time to this problem. His notes are known, which explain the principles of operation of the simplest helicopter.
New era
The global breakthrough in science (and aeronautics in particular) was made by Isaac Newton. After all, the basis of aerodynamics is a comprehensive science of mechanics, the founder of which was an English scientist. Newton was the first to consider the air medium as a conglomerate of particles, which, running into an obstacle, either stick to it or are elastically reflected. In 1726, he presented the theory of air resistance to the public.
Subsequently, it turned out that the environment really consists of the smallest particles - molecules. They learned how to calculate the reflectivity of air quite accurately, and the “sticking” effect was considered an untenable assumption.
Surprisingly, this theory found practical application centuries later. In the 60s, at the dawn of the space age, Soviet designers faced the problem of calculating the aerodynamic drag of descent vehicles of a "blunt" spherical shape, which develop hypersonic speeds upon landing. Due to the lack of powerful computers, it was problematic to calculate this indicator. Unexpectedly, it turned out that it is possible to accurately calculate the drag value and even the pressure distribution over the frontal part using Newton's simple formula regarding the effect of "sticking" of particles to a flying object.
Development of aerodynamics
FounderHydrodynamicist Daniel Bernoulli described in 1738 the fundamental relationship between pressure, density and velocity for incompressible flow, known today as Bernoulli's principle, which is also applicable to calculations of aerodynamic lift. In 1799 Sir George Cayley became the first person to identify the four aerodynamic forces of flight (weight, lift, drag and thrust) and the relationships between them.
In 1871, Francis Herbert Wenham created the first wind tunnel to accurately measure aerodynamic forces. Invaluable scientific theories developed by Jean Le Rond d'Alembert, Gustav Kirchhoff, Lord Rayleigh. In 1889, Charles Renard, a French aeronautical engineer, became the first person to scientifically calculate the power required for sustained flight.
From theory to practice
In the 19th century, inventors looked at the wing from a scientific point of view. And thanks to the study of the mechanism of bird flight, aerodynamics in action was studied, which was later applied to artificial aircraft.
Otto Lilienthal excelled especially in the research of wing mechanics. The German aircraft designer created and tested 11 types of gliders, including a biplane. He also made the first flight on an apparatus heavier than air. For a relatively short life (46 years), he made about 2000 flights, constantly improving the design, which was more like a hang glider than an airplane. He died during the next flight on August 10, 1896, becoming a pioneeraeronautics, and the first victim of a plane crash. By the way, the German inventor personally handed over one of the gliders to Nikolai Yegorovich Zhukovsky, a pioneer in the study of aircraft aerodynamics.
Zhukovsky didn't just experiment with aircraft designs. Unlike many enthusiasts of that time, he primarily considered the behavior of air currents from a scientific point of view. In 1904 he founded the world's first aerodynamic institute at Cachino near Moscow. Since 1918, he headed TsAGI (Central Aerohydrodynamic Institute).
First planes
Aerodynamics is the science that allowed man to conquer the sky. Without studying it, it would be impossible to build aircraft that stably move in air currents. The first aircraft in the usual sense to us was made and lifted into the air on December 7, 1903 by the Wright brothers. However, this event was preceded by careful theoretical work. The Americans devoted a lot of time to debugging the design of the airframe in a wind tunnel of their own design.
During the first flights, Frederick W. Lanchester, Martin Wilhelm Kutta and Nikolai Zhukovsky put forward theories that explained the circulation of air currents that create lift. Kutta and Zhukovsky continued to develop a two-dimensional theory of the wing. Ludwig Prandtl is credited with developing the mathematical theory of subtle aerodynamic and lift forces, as well as working with boundary layers.
Problems and Solutions
The importance of aircraft aerodynamics increased as their speeds increased. Designers began to run into problems with compressing air at or near the speed of sound. Differences in flow under these conditions have led to aircraft handling problems, increased drag due to shock waves, and the threat of structural failure due to aeroelastic flutter. The ratio of flow velocity to the speed of sound was called the Mach number after Ernst Mach, who was one of the first to investigate the properties of supersonic flow.
William John McQuorn Rankine and Pierre Henri Gougoniot independently developed the theory of air flow properties before and after a shock wave, while Jacob Akeret did the initial work on calculating the lift and drag of supersonic airfoils. Theodor von Karman and Hugh Latimer Dryden coined the term "transonic" to describe speeds at the Mach 1 border (965-1236 km/h), when resistance is rapidly increasing. The first sound barrier was broken in 1947 on a Bell X-1 aircraft.
Key Features
According to the laws of aerodynamics, to ensure flight in the earth's atmosphere of any device, it is important to know:
- Aerodynamic drag (X-axis) exerted by air currents on an object. Based on this parameter, the power of the power plant is selected.
- Lift force (Y-axis), providing climb and allowing the device to fly horizontally to the surface of the earth.
- Moments of aerodynamic forces along three coordinate axes acting on a flying object. most importantis the moment of the lateral force along the Z-axis (Mz) directed across the aircraft (conditionally along the wing line). It determines the degree of longitudinal stability (whether the device will "dive" or lift its nose up when flying).
Classification
Aerodynamic performance is classified by airflow conditions and properties, including speed, compressibility and viscosity. External aerodynamics is the study of flow around solid objects of various shapes. Examples are assessing the lift and vibrations of an aircraft, as well as the shock waves that form in front of a missile's nose.
Internal aerodynamics is the study of airflow moving through openings (passages) in solid objects. For example, it covers the study of flows through a jet engine.
Aerodynamic performance can also be classified according to flow speed:
- Subsonic is called a speed less than the speed of sound.
- Transonic (transonic) - if there are speeds both below and above the speed of sound.
- Supersonic - when the flow speed is greater than the speed of sound.
- Hypersonic - the flow speed is much greater than the speed of sound. Usually this definition means speeds with Mach numbers above 5.
Helicopter aerodynamics
If the principle of aircraft flight is based on the lifting force during translational motion exerted on the wing, then the helicopter, as it were, creates lift by itself due to the rotation of the blades in the axial blowing mode (that is, without translational speed). Thanks toWith this feature, the helicopter is able to hover in the air in place and perform energetic maneuvers around the axis.
Other applications
Naturally, aerodynamics is applicable not only to aircraft. Air resistance is experienced by all objects moving in space in a gas and liquid medium. It is known that aquatic inhabitants - fish and mammals - have streamlined shapes. On their example, you can trace the aerodynamics in action. Focusing on the animal world, people also make water transport pointed or teardrop-shaped. This applies to ships, boats, submarines.
Vehicles experience significant air resistance: it increases as speed increases. To achieve better aerodynamics, cars are given a streamlined shape. This is especially true for sports cars.
