There are two types of propellers:

This is a fixed pitch propeller propeller that his attack angle constant, the change in speed craft operations by changing the speed of rotation of the blades.

Variable pitch propeller propeller it can change the angle of attack of the blades, so you can change the speed of the vehicle by changing the angle of attack, which reduces engine wear (when necessary reverse is not necessary to operate the engine in the opposite direction, but only a change in angle of attack). Such propeller also installed in helicopters (main rotor), which also changes the angle while the rotor movement and due to a manual command. Also such propellers installed passenger aircraft and transport, when reversing stride use to stop a plane landing, immediately after touching track.

Aerodynamic - a surface that produces lift Wings. Height stabilizer. Adjust stabilizer. Propeller. Fuselage.

Aircraft with a long wingspan are often more effective, because they have less resistance and turbulence induced tips of their wings do not affect much on the wing. However, long wings torque shall mean Slmtos have greater persistence its longitudinal axis, so he can not turn and maneuver quickly. Therefore, fighter planes and jets Irovtika have a relatively short wingspan, aiming to improve maneuverability.

Since the wing produces lift force proportional to the area of ​​the wing, short-winged aircraft wing width required to be larger. The ratio of the length of the wings of the plane widths is very important in determining the flight characteristics. Aviation engineers call this entry "length-width ratio of the wing."

The relative flow speed / relative wind - air flow can be made when the plane is the ground and the wind is blowing strong enough Molo.am plane will rise into the air and fall (that moment, the air flow is no longer relatively) .zrm air plane movement can be made within the air mass. Which means that the terms of the elevation is within Goshawir aircraft movement and the creation of a relatively spirit by Tnoato.mhirot real air - the relative speed between the object moves in a block of air, and the bloc Hawir.cl following speeds are "true air speed", unless otherwise indicated.

Aerodynamic profiles terminology [edit source | edit]

 

Aerodynamic profile terminology

Here are some terms related to aerodynamic profiles [5]

Upper surface (upper surface) is usually given greater speed and lower pressure.

Lower surface (lower surface): usually given a smaller speed and greater pressure. Differential pressure between the surfaces contributes to the elevation.

Offensive language (pronounced leading edge): The point at the front of her profile maximum curvature (minimum radius of curvature).

Flow Language (trailing edge) as leading edge only for the back of the profile.

Aerodynamic chord (chord line): a straight line connecting the leading edge trailing edge. Usually marked string length c. The string length is typical length of the profile.

Hakimon line (camber line): a leading edge trailing edge which is equal on both surfaces profile. Shape depends on the thickness distribution along the string.

Thickness profile changes along the string. Thickness can be evaluated on the basis of two ways:

Perpendicular to the string. [6] called "British convention".

Perpendicular to the line Hakimon. [7] [8] called "American convention".

In addition, important parameters to describe the behavior of fluid motion profile are:

Center Haaoirodinmi: The distance along the string from the edge of the attack, in which the torque is not dependent on the coefficient of lift or angle of attack. At this point.

Central pressure: The distance along the string from the edge of the attack, in which the torque is reset.

Aerodynamics, aerodynamic profile is the shape of the cut of the wing (of the propeller, rotor or turbine). Even commentators attribute aerodynamic profile.

 

Typical aerodynamic profile

Aerodynamic profile shape is an important parameter affecting the performance of the aircraft lift force generation as the drag force as a result of air flow profile. Body aerodynamic profile which produces fluid moving aerodynamic force. This force is caused by the relative motion between the body and flows. Generally speaking, this force contributions contributed to pressure on body language (buoyancy force) in the perpendicular to it and the contribution due to shear viscosity (drag force). Aerodynamic profiles of sub-sonic tools usually characterized by a round attack language, the language of sharp flow asymmetry between the top surface and the bottom surface. Profile has a similar function in which water is flowing is called fin.

The lift on the profile is a direct result of his attack angle geometric shape. When tilted at a certain angle profile, and affects the flow leading to it, running in the opposite direction toward the force diversion of flows. This force is called the aerodynamic force. Most profiles need any tilt angle to create lift, but non-symmetrical profiles can do it even without the angle of attack. Diversion of flows near the profile causes biased flow lines. As a result, get a pressure gradient between the two sides of the profile (and differences in speeds, according to Bernoulli's equation). Using the principle of circulation, Kota G'kovsky theory, and the speed difference between the top and bottom of the profile, you can calculate the buoyancy.

 

Aircraft wings

 

Unlike animal wings, the wings of the aircraft are not moving, and therefore need to provide lift only because of their shape. For a moving plane, wings reports a certain amount of air, which means that they exert a force on the air. Due to the law of action and reaction, air force wings running back. The deferred amount of air the wings down and up depending on the shape and angle in which they are placed. Lift occurs when the power is running air under the wing up will be a big force used by air over the wing down. Pressure above the wing lift force acting upon it will be less pressure under it.

Modern aircraft, the wings are made - such as the fuselage itself - aluminum and magnesium alloys, two metals toughness and ease. Hollow wings contain the majority of the fuel used in aircraft engines; The program is an extensive network of pipes leading to the wing fuel to the engine. Many aircraft wings are used to carry the engines themselves, and sometimes fuel tanks and munitions.

Aircraft wings are shaped in different ways, depending on the required performance and the speed of the plane. Delta wings, for example, are in the form of a straight-angle triangle, like the Lavi aircraft and Israeli Kfir and Mirage 3 and the French Concorde, delta wings are particularly effective for flights at supersonic speed high. Some aircraft, like the F-14, F-111 and the US Navy and the Russian Sukhoi Su-17, a variable geometry wings cost, that can be a Pharisee situation almost vertical fuselage and huddled situation stick fuselage. Clustered situation is for high speeds and low speeds interpretation. Variable geometry wings combine cost advantage of delta wings and traditional wings, but the mechanism by which they move is heavy, expensive, complicated and time faults; Has been discontinued production of aircraft with variable geometry wings with in the 80s, and is now replacing them new technologies.

 

Irodinmika

Aerodynamics is a branch flow mechanics deals with the calculation of the forces and moments acting on the body because of the airflow around it. Such calculation conditional understanding the flow field around the body. Flow field characteristics given by the velocity, pressure, density and temperature of the air around the body at any point and at any time. You can find these qualities theoretically or by experiment. Experimentally measure the flow properties, usually in wind tunnel, although there is also the possibility to make measurements more realistic conditions. The results are shown by graphs or empirical formulas of some or all of the new flow field. Of course Slmdida wind tunnel has its limitations and sometimes it is difficult to conclude what would be such measurement flow properties when they are required real terms. In theory it is necessary to formulate equations describing the conservation laws of mass, momentum and energy for the flow field in question. Solving equations can be done analytically (exact mathematical solution of the equations), with simplicity and approximations, or by numerical calculations (CFD).

 

Aerodynamic system

Since most of the systems under study are not closed but permeability, define two sizes imaginary "Volume Control" and Perimeter Control "for open systems:

Control volume (Volume Control) - a space whose location and boundaries of arbitrary shape can vary in time.

Surface Control (Control Surface) - area of ​​the control volume.

An example of this is part of a pipe in which there is a flow. We can set the volume control as the largest cylinder contained within the tube and then we can say that through an area not undergoing mass shell.

Aerodynamic forces on a plane

A key goal of aerodynamics is to predict the aerodynamic forces acting on the plane.

The four fundamental forces acting on a motorized plane are: lift, weight, thrust and drag.

Aerodynamic forces acting on the plane

(Painted wing profile)

The weight is the force generated due by the gravitational pull and the drive is power generated by the engine. They lift and drag forces generated by the relative motion of the body in the air. Aerodynamic lift is defined as a force acting perpendicular to the relative flow of air and aerodynamic drag is defined as a force acting parallel to the relative flow. The lift is defined as positive when it is facing up while the drag is defined as positive when run backwards.

Angle of attack

 

Black arrows in this diagram represent the direction of the wind. Alpha angle is the angle of attack

Angle of attack (angle of attack-AOA), in aviation is the angle between a particular aerodynamic surface (wings, tail, Kennard, etc.) and the relative wind direction. In other words, the angle of attack is measured between the string and the direction of progress.

There is a bio-separation angle of attack of the wing angle of attack of the aircraft, as it relates to the angle of the wing between wing average profile overwhelming flow velocity, angle of attack of the aircraft refers to the angle between the longitudinal axis of the jet flow flooding. Given the structure of the plane is known, it is possible to get out of the corner General induced angle of attack various flaps.

The term is particularly relevant for the progress of space containing gas or liquid. The greater the angle of attack, the greater the reaction force of the gas or liquid applied to the surface. Since power is equivalent to the angle between the direction of progress attack, and in the case of aircraft increased buoyancy The greater the angle of attack of the wing or propeller or rotor blade, but only up to a point called "stall angle", beyond which a buoyancy to capacity.

Highest angle of attack to date, which remains stable over a plane more than 10 seconds is 89.8 °, established by a series of family aircraft Su-37 / Su-35 Russian.

Applications

The main use appears beacon attack angles Christian forces overwhelming flow body. In general we can say that the greater angle of attack, the force acting on the body will be greater, but at major attack, the flow is cut off from the body in a process called "stall" the body loses the forces acting on it. Power costs a profile provided by

 

Aerodynamic profile

Aerodynamics, aerodynamic profile is the shape of the cut of the wing (of the propeller, rotor or turbine). Even commentators attribute aerodynamic profile.

 

Typical aerodynamic profile

Aerodynamic profile shape is an important parameter affecting the performance of the aircraft lift force generation as the drag force as a result of air flow profile. Body aerodynamic profile which produces fluid moving aerodynamic force. This force is caused by the relative motion between the body and flows. Generally speaking, this force contributions contributed to pressure on body language (buoyancy force) in the perpendicular to it and the contribution due to shear viscosity (drag force). Aerodynamic profiles of sub-sonic tools usually characterized by a round attack language, the language of sharp flow asymmetry between the top surface and the bottom surface. Profile has a similar function in which water is flowing is called fin.

The lift on the profile is a direct result of his attack angle geometric shape. When tilted at a certain angle profile, and affects the flow leading to it, running in the opposite direction toward the force diversion of flows. This force is called the aerodynamic force. Most profiles need any tilt angle to create lift, but non-symmetrical profiles can do it even without the angle of attack. Diversion of flows near the profile causes biased flow lines. As a result, get a pressure gradient between the two sides of the profile (and differences in speeds, according to Bernoulli's equation). Using the principle of circulation, Kota G'kovsky theory, and the speed difference between the top and bottom of the profile, you can calculate the buoyancy.

Propeller

 

A five-ship propeller blades

Propeller (propeller foreign language, is also called in the context of helicopter rotor) is a mechanical component that converts rotary motion to propel drive vehicles such as aircraft, ship, or submarine, through a medium flows, such as fluid (eg, water) or gases (eg, air) by turning two curved blades, or more, around a central axis, similar to the way round screw in a solid material. Aircraft propeller blades act like wings rotate and create power in the manner described combination of Bernoulli's equation and Newton's third law, when they create a difference in air pressure on the front surface opposed to the back surface of the blades and by moving the fluid (air, in the case of a plane) where they meet, to the back of the propeller.

There are two types of propellers:

This is a fixed pitch propeller propeller that his attack angle constant, the change in speed craft operations by changing the speed of rotation of the blades.

Variable pitch propeller propeller it can change the angle of attack of the blades, so you can change the speed of the vehicle by changing the angle of attack, which reduces engine wear (when necessary reverse is not necessary to operate the engine in the opposite direction, but only a change in angle of attack). Such propeller also installed in helicopters (main rotor), which also changes the angle while the rotor movement and due to a manual command. Also such propellers installed passenger aircraft and transport, when reversing stride use to stop a plane landing, immediately after touching track.

External links

 

Flow lines around the profile NACA 0012 at a moderate attack

The wings, horizontal and vertical stabilizers of aircraft available with aerodynamic profiles cuts. Aerodynamic profiles are also used helicopter propellers, fans and turbines. Sails are aerodynamic profiles, as well as underwater surfaces of keel boats as an order similar function. Many animals and even some plants use the principles of aerodynamic profiles. Examples are birds, fish and sea urchins. Profile aerodynamic lift force can produce the vehicles, helping to pushing.

Every body has given flow angle of attack, such as braces, a building or a bridge, create aerodynamic force called lift, direction perpendicular to the flow. Planning aerodynamic profiles typically aim is to increase the lift as possible and Maidf over from the other hand to reduce drag.

 

Lift and drag coefficients for typical profile

On the left you can see a graph illustrating the variability of lift and drag coefficients wind tunnel experiment. The graph represents a non-symmetrical profile and therefore depletion is also produced zero attack angle. At first, with increasing angle of attack, the lift coefficient exceeds approximately linear (almost constant slope), but at about 18 degrees there is a stall and lift coefficient falls rapidly. The fall of the upper promotes detachment occurs because the upper surface boundary layer. Effective, changing the thickness of the boundary layer changes the shape of the profile and reduces the effectiveness of the asymmetry of the profile by reducing circulation around it and consequently also the lift. Growth thickness of the boundary layer causes also add drag, and can be seen in the vicinity of a stall there is a rapid growth coefficient of drag.

Aerodynamic profile design is a significant consideration in the field of aerodynamics. There are different types of profiles in various areas of airports. Non-symmetric profiles capable of producing power lift without angle of attack, while the symmetrical profiles are more typical inverted flight aerobatics aircraft. Profile symmetric tip the scales and wings domain for increasing angles of attack allowed without stall. Thus, many attack angles can be realized without separation of the upper surface boundary layer.

Profiles of aircraft sonic language characterized by a sharp attack, and generally nasty than the profiles of aircraft sub-sonic. The sharp leading edge angles causes high sensitivity attack. By increasing the thickness of the profile in the leading edge can cause the flow of sound to move to the subsonic. Profiles used for flights to voice usually have low curvature to allow faster flight without a significant increase in Gerar. Modern aircraft wings, is a discernible shift along the wing aerodynamic profile, which is suitable for all wing area corresponding profile in characteristic flow.

Most aircraft wings are installed on the shelves. From the trailing edge of the profile can be used in the balance, but in contrast to the balance, the shelf can partially enter the wing when not in use.

Nimer wing designed for flow line has a maximum thickness of maximum curvature in the middle of the wing. You can with Naoya-Stokes equations show that the linear field, the negative pressure gradient along the flow Consider downloading speed. Therefore, the maximum curvature in the middle, keeping the laminar flow wing in many more will be possible for higher cruise speeds. However, the presence of external factors such as rain or interfere on the wing, it does not work because the flow Laminaria no longer maintained.

NACA profiles are aerodynamic profiles developed by the National Advisory Committee for Aeronautics of the United States. NACA has defined a number of equations that produce wing profiles by setting 4 digits:

Book # 1: The maximum percentage curve length string.

Book # 2: The distance of tens of percent maximum curve (the length of the string) from the edge of the attack.

Literature # 3.4: Percent maximum thickness profile string length.

With four digits of NACA profiles can be defined geometric shape of the profile in question and to draw on the aerodynamic characteristics. Today, there are programs designed wing profiles according to design requirements, such as PROFOIL, XFOIL, AeroFOIL. [4]

Aerodynamic profiles terminology

 

Aerodynamic profile terminology

Here are some terms related to aerodynamic profiles:

Upper surface (upper surface) is usually given greater speed and lower pressure.

Lower surface (lower surface): usually given a smaller speed and greater pressure. Differential pressure between the surfaces contributes to the elevation.

Offensive language (pronounced leading edge): The point at the front of her profile maximum curvature (minimum radius of curvature).

Flow Language (trailing edge) as leading edge only for the back of the profile.

Aerodynamic chord (chord line): a straight line connecting the leading edge trailing edge. Usually marked string length c. The string length is typical length of the profile.

Hakimon line (camber line): a leading edge trailing edge which is equal on both surfaces profile. Shape depends on the thickness distribution along the string.

Thickness profile changes along the string. Thickness can be evaluated on the basis of two ways:

Perpendicular to the string. [6] called "British convention".

Perpendicular to the line Hakimon. [7] [8] called "American convention".

In addition, important parameters to describe the behavior of fluid motion profile are:

Center Haaoirodinmi: The distance along the string from the edge of the attack, in which the torque is not dependent on the coefficient of lift or angle of attack. At this point \ frac {\ partial (C_ {M '})} {\ partial (C_L)}=0.

Central pressure: The distance along the string from the edge of the attack, in which the torque is reset.

Thin wing theory [edit source | edit]

Thin wing theory was developed by the German-English mathematician Max Mnk and was held by the British Hawirodinmai Herman Glaurt and others [9], in the 20s of the 20th century. This is a simple descriptive connecting the elevation angle of attack incompressible flows and non-viscosity. The theory makes the approximation of the flow around a two-dimensional flow profile around the slim profile.

While issuing theory is great reason was treated provided the basis for important features of two-dimensional flow profiles:

Symmetric profile, aerodynamic center and center are within a quarter of pressure from the other edge of the attack.

Curved profile, aerodynamic center is within a quarter from the other edge of the attack.

The slope of the graph lift coefficient against the angle of attack is 2 \ pi \! Radian. It expanded to Munich when the angle of attack is defined in relation to the string.

Thin wing theory does not account for the phenomenon of stalling. [10]

As a result of the 3 to get the lift coefficient for a curved profile infinite wingspan is:

 

Navajo thin wing profile. According to the theory of Kota-G'kovsky:

L ^ \ prime=- \ rho_ \ infty V_ \ infty \ Gamma, \,

That is, contained per unit length equal to the product of the fluid density, flow velocity and circulation, which is defined by:

\ Gamma=\ oint_ {C} V \ cdot d \ mathbf {s}=\ oint_ {C} V \ cos \ theta \; ds \,=\ int_ {C} \ gamma (x) d {x}

 

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