This drag force occurs in airplanes due to wings or a lift body redirecting air to cause lift, and in cars with airfoil wings that redirect air to cause downforce. Samuel Langley noticed that flatter, higher aspect ratio plates had higher lift and lower drag and were introduced in 1902. Without the invention of the aerodynamic quality of the aircraft, modern aircraft design would be impossible.
Lifting and moving
The total aerodynamic force acting on a body is usually considered to consist of two components: lift and displacement. By definition, the force component parallel to the counter flow is called displacement, while the component perpendicular to the counter flow is called lift.
These basics of aerodynamics are of great importance for the analysis of the aerodynamic quality of the wing. Lift is produced by changing the direction of flow around the wing. Changedirection results in a change in speed (even if there is no change in speed, as seen in uniform circular motion), which is acceleration. Therefore, to change the direction of flow, a force is required to be applied to the fluid. This is clearly visible on any aircraft, just look at the schematic representation of the aerodynamic quality of the An-2.
But not everything is so simple. Continuing the theme of aerodynamic quality of a wing, it is worth noting that creating air lift below it is at a higher pressure than the air pressure above it. On a finite span wing, this pressure difference causes air to flow from the root of the lower surface wing to the base of its upper surface. This flying airflow combines with flowing air to cause a change in speed and direction that twists the airflow and creates vortices along the trailing edge of the wing. The vortices created are unstable, they quickly combine to create wing vortices. The resulting vortices change the speed and direction of the airflow behind the trailing edge, deflecting it downward and thereby causing a flap behind the wing. From this point of view, for example, the MS-21 aircraft has a high level of lift-to-drag ratio.
Air flow control
The vortexes in turn change the airflow around the wing, reducing the wing's ability to generate lift, so it requires a higher angle of attack for the same lift, which tilts the total aerodynamic force backwards and increases the drag component of that force. Angular deviation is negligibleaffects lift. However, there is an increase in drag equal to the product of the lift and the angle due to which it deviates. Since deflection is itself a function of the lift, the additional drag is proportional to the angle of climb, which can be clearly seen in the A320's aerodynamics.
Historical examples
A rectangular planetary wing creates more vortex vibrations than a conical or elliptical wing, which is why many modern wings are tapered to improve lift-to-drag ratio. However, the elliptical airframe is more efficient as the induced wash (and hence the effective angle of attack) is constant across the entire span of the wings. Due to manufacturing complications, few aircraft have this planform, the most famous examples being the World War II Spitfire and the Thunderbolt. Tapered wings with straight leading and trailing edges can approach an elliptical lift distribution. As a general rule, straight, untapered wings produce 5% and tapered wings produce 1-2% more induced drag than an elliptical wing. Therefore, they have better aerodynamic quality.
Proportionality
A high aspect ratio wing will produce less induced drag than a low aspect ratio wing because there is less air disturbance at the tip of a longer, thinner wing. Therefore, the inducedresistance can be inversely proportional to proportionality, no matter how paradoxical it may sound. The lift distribution can also be changed by washing out, twisting the wing around to reduce the drop towards the wings, and by changing the airfoil near the wings. This allows you to get more lift closer to the wing root and less to the wing, which leads to a decrease in the strength of the wing vortices and, accordingly, to an improvement in the aerodynamic quality of the aircraft.
In the history of aircraft design
On some early aircraft the fins were mounted on the tips of the tails. Later aircraft have a different wing shape to reduce the intensity of the vortices and achieve maximum lift-to-drag ratio.
Rooftop vane fuel tanks can also provide some benefit by preventing chaotic air flow around the wing. Now they are used in many aircraft. The aerodynamic quality of the DC-10 was deservedly considered revolutionary in this respect. However, the modern aviation market has long been replenished with much more advanced models.
Drag-to-drag formula: explained in simple terms
To calculate the total resistance it is necessary to take into account the so-called parasitic resistance. Since induced drag is inversely proportional to the square of airspeed (at a given lift), while parasitic drag is directly proportional to it, the overall drag curve shows the minimum speed. Airplane,flying at such speed, operates with optimal aerodynamic qualities. According to the above equations, the speed of minimum resistance occurs at a speed at which the induced resistance is equal to the parasitic resistance. This is the speed at which the optimum slip angle is reached for idle aircraft. In order not to be unfounded, consider the formula on the example of an aircraft:
The continuation of the formula is also quite curious (pictured below). Flying higher, where the air is thinner, will increase the speed at which the minimum drag occurs, and thus it allows faster travel on the same amount of fuel.
If an aircraft flies at its maximum allowable speed, then the altitude at which the air density will provide it with the best aerodynamic quality. Optimal altitude at maximum speed and optimal speed at maximum altitude may change during flight.
Stamina
Speed for maximum endurance (i.e. time in the air) is the speed for minimum fuel consumption and less speed for maximum range. Fuel consumption is calculated as the product of the required power and the specific fuel consumption per engine (fuel consumption per unit of power). The required power is equal to the drag time.
History
The development of modern aerodynamics began only in the XVIIcenturies, but aerodynamic forces have been used by humans for thousands of years in sailboats and windmills, and images and stories of flight appear in all historical documents and works of art, such as the ancient Greek legend of Icarus and Daedalus. The fundamental concepts of continuum, resistance, and pressure gradients appear in the work of Aristotle and Archimedes.
In 1726, Sir Isaac Newton became the first person to develop the theory of air resistance, making it one of the first arguments about aerodynamic qualities. The Dutch-Swiss mathematician Daniel Bernoulli wrote a treatise in 1738 called Hydrodynamica in which he described the fundamental relationship between pressure, density and flow velocity for incompressible flow, known today as Bernoulli's principle, which provides one method for calculating aerodynamic lift. In 1757, Leonhard Euler published the more general Euler equations, which can be applied to both compressible and incompressible flows. The Euler equations were extended to include the effects of viscosity in the first half of the 1800s, giving rise to the Navier-Stokes equations. Aerodynamic performance/aerodynamic quality of the polar was discovered around the same time.
Based on these events, as well as research done in their own wind tunnel, the Wright brothers flew the first plane on December 17, 1903.
Types of aerodynamics
Aerodynamic problems are classified by flow conditions or flow properties, including characteristics such as velocity, compressibility and viscosity. They are most often divided into two types:
- External aerodynamics is the study of flow around solid objects of various shapes. Examples of external aerodynamics are the assessment of lift and drag on an aircraft, or shock waves that form in front of a missile's nose.
- Internal aerodynamics is the study of flow through passages in solid objects. For example, internal aerodynamics covers the study of airflow through a jet engine or through an air conditioning chimney.
Aerodynamic problems can also be classified according to flow speeds below or near the speed of sound.
The problem is called:
- subsonic, if all velocities in the problem are less than the speed of sound;
- transonic if there are speeds both below and above the speed of sound (usually when the characteristic speed is approximately equal to the speed of sound);
- supersonic, when the characteristic flow velocity is greater than the speed of sound;
- hypersonic, when the flow velocity is much greater than the speed of sound.
Aerodynamicists disagree on the exact definition of hypersonic flow.
The effect of viscosity on flow dictates a third classification. Some problems may only have very small viscous effects, in which case the viscosity may be considered negligible. Approximations to these problems are called inviscidcurrents. Flows for which viscosity cannot be neglected are called viscous flows.
Compressibility
An incompressible flow is a flow in which the density is constant both in time and space. Although all real fluids are compressible, flow is often approximated as incompressible if the effect of a change in density causes only small changes in the calculated results. This is more likely when the flow rate is well below the speed of sound. The effects of compressibility are more significant at speeds close to or higher than the speed of sound. The Mach number is used to evaluate the possibility of incompressibility, otherwise compressibility effects must be included.
According to the theory of aerodynamics, the flow is considered compressible if the density changes along the streamline. This means that, in contrast to an incompressible flow, changes in density are taken into account. In general, this is the case when the Mach number of part or all of the flow exceeds 0.3. The Mach value of 0.3 is rather arbitrary, but it is used because a gas flow below this value exhibits less than 5% density changes. Also, the maximum density change of 5% occurs at the stagnation point (the point on the object where the flow velocity is zero), while the density around the rest of the object will be much lower. Transonic, supersonic and hypersonic flows are all compressible.
Conclusion
Aerodynamics is one of the most important sciences in the world today. She provides usbuilding quality planes, ships, cars and comic shuttles. It plays a huge role in the development of modern types of weapons - ballistic missiles, boosters, torpedoes and drones. All this would not have been possible if it were not for modern advanced concepts of aerodynamic quality.
Thus, ideas about the subject of the article changed from beautiful, but naive fantasies about Icarus, to functional and really working aircraft that arose at the beginning of the last century. Today we cannot imagine our lives without cars, ships and aircraft, and these vehicles continue to improve with new breakthroughs in aerodynamics.
The aerodynamic qualities of gliders were a real breakthrough in their time. At first, all discoveries in this area were made by means of abstract, sometimes divorced from reality, theoretical calculations, which were carried out by French and German mathematicians in their laboratories. Later, all their formulas were used for other, more fantastic (by the standards of the 18th century) purposes, such as calculating the ideal shape and speed of future aircraft. In the 19th century, these devices began to be built in large quantities, starting with gliders and airships, the Europeans gradually switched to the construction of aircraft. The latter were first used exclusively for military purposes. The aces of the First World War showed how important the issue of dominance in the air is for any country, and the engineers of the interwar period discovered that such aircraft are effective not only for the military, but also for civilians.goals. Over time, civil aviation has firmly entered our lives, and today not a single state can do without it.
