A large number of various magazines that collect and analyze information related to the achievements and problems of aviation often focus readers on the material aspects of the work and structure of modernized devices such as airplanes, rockets, helicopters and other aircraft. Often, all phenomena that occur with the internal and external structure of the vehicle during the flight are also analyzed. Usually the contrail reflects this. Many people watch beautiful planes that leave a flat line in flight.
The concept of this phenomenon
The contrail is formed in the tropopause. Its appearance is influenced by water vapor, which undergo enhanced condensation. They are present in the combustion products, since hydrocarbons are evenly consumed during combustion.fuel. After exiting and sufficient cooling, a bright contrail from an aircraft or other aircraft in the air becomes noticeable.
There are special airshows that are advisable to hold only in sunny weather. These events are organized at airfields that have the status of the largest in the world. At this time, a large number of spectators enthusiastically watch the movement of many aircraft, making interesting maneuvers in the air. The main distinguishing feature of such events is the leaving of a bright trail from each vehicle. It is often done so that each plane has its own tail color, which helps to get the most vivid and memorable effect.
Unlike airplanes, rockets constantly leave behind massive, even often formidable traces that look not only large-scale, but also have a rich color. They are issued from combat aircraft. This procedure can be observed not only when going to special events, but also being on the street or turning on the TV on the channel of interest. This way you can see the contrail.
Tip vortex of the wing
It should be remembered that an airplane in flight leaves behind a limited and fairly wide area of the atmosphere, which becomes perturbed, its composition changes for a long time. This phenomenon is often referred to as a tangled trail. It usually appears under the action of jet engines, since during operation they constantly interact withenvironment. The end vortices of the aircraft wings also take part in this process.
If we compare the significantly negative impact on the environment, then the primacy is always given to the tip vortices of the wings. There are many conventions for tangled tracks, but most often they are drawn on special schemes in the likeness of a sheet with unusual edges, the ends of which are completely twisted, that is, you can compare them with vortices.
The twisting process: scientific reasoning
The twisting process can be easily explained scientifically. There is a clear difference in pressure between both sides of the wings of the aircraft, that is, on their upper and lower surfaces. The air is gradually redistributed from the lower surface, as it experiences the most increased pressure, to the upper one in order to remain in the area with the lowest pressure.
This redistribution occurs through the tip of each wing, which creates powerful and very noticeable vortices. The force of the pressure difference is important, since the lifting force depends on it. It is this value that has a strong influence on the wing. The stronger this effect, the more powerful and relief the vortices are formed.
Various brands of aircraft with wing tip vortex
The speed of air currents sometimes changes, but it can be roughly determined that if the diameter of the vortex wake is about 8-15 m, we should talk about a value of 150 km / h. The end vortex canbe formed in different ways. This process depends on the brand, configuration of the aircraft. The powerful Mirage 2000 and F-16C fighters deserve attention if they move into a high angle of attack flight position.
The process of emergence of the tip vortex
The end vortex is visualized thanks to a special tracer generator responsible for the proper representation of the smoke trail. The action of this element is due to a change in the state of the atmosphere, which lasts for quite a long time. Then the peripheral speed gradually subsides, that is, the visual object is lost and disappears.
Under the influence of time, the circumferential speed of the vortex decays, due to which the visual image changes shape until it completely dissolves. The perceived intensity of the whirlwind can last up to about two minutes after the aircraft has passed a particular location. Such a vortex has the ability to significantly affect the flight mode of an aircraft that has entered the atmosphere disturbed by the action of the engine of the previous vehicle.
Long-term observation of the tip vortex
When the vortices are interacting with each other, they slowly descend and diverge, that is, a perceptible change in the atmosphere disappears. The contrail of an aircraft is an excellent object for observing its transformations. After about 30 - 40 seconds, it begins to change shape, as it is strongly influenced by a whirlwind, which gradually develops. When they intersectinversion, and vortex layers, bizarre shapes are created that can be calculated in advance, since various patterns act on the process of their formation.
The number of stripes and the height of the contrail is controlled by the number and location of engines in the system. At the same time, the contrail not only floats in the air, but also constantly changes, creating interesting contours. Most often, twisting of this layer is observed under the influence of the end vortex. All transformations of the layer reflect the various aerodynamic processes that are always formed during the flight.
Separated-vortex flows
Sometimes pilots are forced to perform various attacks, which are carried out with a large angle of inclination of more than 20 degrees. In this case, the nature of the flow around the contours of the aircraft changes significantly for a while. Separation areas begin to appear, which are mainly fixed near the upper surface of the wing and fuselage. In them, the pressure is greatly reduced, so the concentration and increase of atmospheric moisture immediately begins. Thanks to this aspect, it is possible to observe the flight of an aircraft without the use of tracers.
Conditions for the appearance of a separation-vortex effect
If the angle of attack is too large, a significant cloud halo will form around the aircraft. When the plane flies, this cloud automatically turns into a vortex contrail from the plane. Typically, bombers develop separation areas near the wings, whichthe appearance of a vortex rope is clearly observed. This is what a contrail looks like, the photos of which are always fascinating.
Hot traces of missiles
Sometimes, when launching rockets, one has to deal with such cases when there is a stall flow in the area of the gas-air path located in the rocket power plant. The gas jet leaving the rocket engine has a high temperature, so sometimes it enters the air intake of the carrier aircraft, which happens when the device is set to certain modes.
The airflow becomes too uneven in temperature as it is exposed to elevated temperature gases, causing the air entering the engine to become altered. An engine surge is formed, that is, a stall occurs in the system. To reveal this process, the main combustion chambers are observed, since the air flow is subjected to longitudinal oscillations, passing through the engine tract, and then marked by the release of a flame from these elements. This is how a contrail from a rocket appears.
Features of the contrail during testing
Often missile launches are carried out in the concept of testing. An exception is the on-board equipment, which serves for the purpose of recording and storing information. Often, the photographic aircraft is released along with the carrier, while the process of filming is carried out, which allows you to capture the whole phenomenon on camera. You can often find such a contrail from a rocketBuk.
Rocket launches are often carried out at relatively low speeds in order to better capture the whole process. In this case, engine surge is often formed, since hot gases enter the rocket engine in jets, which disables its air intake. Flame ejection is immediately noted, which is typical when a surge occurs. This is how the FSX contrail is expressed.
This incident causes the engine to stop. These features after the study helped to create a number of different systems, the tasks of which include timely diagnosis of surge, taking measures to eliminate it, as well as transferring the engine to the optimal operating mode with constant maintenance of its optimal state. In this case, missile weapons expand the scope, while at each engine operation mode, these aircraft are able to show the most stable state.
Fireball in the air
The tests of the MiG-29 aircraft were carried out, which consisted in refueling. During one of the flights, the release of fuel liquid into the atmosphere was recorded, which was preceded by depressurization of the fuel pipeline. With the help of an aircraft-photographer, this unusual situation was recorded. At the same time, a certain part of the fuel got into the engine, which almost immediately led to its shutdown due to surge.
Besides the ejection of the flame, which always happens when the engine surges, there was an ignition of the fuel that went through the air channel. After that, the flame engulfed all the fuel and went beyond the limits of the internalconstruction, but almost instantly was demolished by the oncoming air flow. Because of this situation, an unusual phenomenon appeared, which was called a fireball. This Buk contrail is also capable of transmitting.
A bright afterburner trail
Modern fighter aircraft have an engine that is equipped with adjustable nozzles, classified as supersonic. When the afterburner mode is activated, the pressure at the nozzle exit is much higher than that of the surrounding air masses. If you analyze the space at a considerable distance from the nozzle, the pressure gradually equalizes. This aspect during the movement of the aircraft leads to increased production of gas, which leads to the formation of a bright contrail from the aircraft, which appears when the aircraft is moving.
