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Camber (aerodynamics)
In aeronautics and aeronautical engineering, camber is the asymmetry between the two acting surfaces of an airfoil, with the top surface of a wing (or correspondingly the front surface of a propeller blade) commonly being more convex (positive camber). An airfoil that is not cambered is called a ''symmetric airfoil''. The benefits of cambering were discovered and first utilized by George Cayley in the early 19th century. Overview Camber is usually designed into an airfoil to maximize its lift coefficient. This minimizes the stalling speed of aircraft using the airfoil. An aircraft with cambered wings will have a lower stalling speed than an aircraft with a similar wing loading and symmetric airfoil wings. An aircraft designer may also reduce the angle of attack of the outboard section of the wings. This ensures that, as the aircraft approaches the stall, the wing root stalls before the tip, giving the aircraft resistance to spinning and maintaining aileron effectiveness c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerodynamic Camber
Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dynamics and its subfield of gas dynamics. The term ''aerodynamics'' is often used synonymously with gas dynamics, the difference being that "gas dynamics" applies to the study of the motion of all gases, and is not limited to air. The formal study of aerodynamics began in the modern sense in the eighteenth century, although observations of fundamental concepts such as aerodynamic drag were recorded much earlier. Most of the early efforts in aerodynamics were directed toward achieving heavier-than-air flight, which was first demonstrated by Otto Lilienthal in 1891. Since then, the use of aerodynamics through mathematical analysis, empirical approximations, wind tunnel experimentation, and computer simulations has formed a rational basis for t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersonic Flight
A supersonic aircraft is an aircraft capable of supersonic flight, that is, flying faster than the speed of sound (Mach number 1). Supersonic aircraft were developed in the second half of the twentieth century. Supersonic aircraft have been used for research and military purposes, but only two supersonic aircraft, the Tupolev Tu-144 (first flown on December 31, 1968) and the Concorde (first flown on March 2, 1969), ever entered service for civil use as airliners. Fighter jets are the most common example of supersonic aircraft. The aerodynamics of supersonic flight is called compressible flow because of the compression associated with the shock waves or "sonic boom" created by any object traveling faster than sound. Aircraft flying at speeds above Mach 5 are called hypersonic aircraft. History The first aircraft to fly supersonic in level flight was the American Bell X-1 experimental plane which was powered by a thrust rocket powered by liquid oxygen and ethyl alcohol. Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zero-lift Axis
A cambered aerofoil generates no lift when it is moving parallel to an axis called the zero-lift axis (or the zero-lift line.) When the angle of attack on an aerofoil is measured relative to the zero-lift axis it is true to say the lift coefficient is zero when the angle of attack is zero. For this reason, on a cambered aerofoil the zero-lift line is better than the chord line when describing the angle of attack. When symmetric aerofoils are moving parallel to the chord line of the aerofoil, zero lift is generated. However, when cambered aerofoils are moving parallel to the chord line, lift is generated. (See diagram at right.) For symmetric aerofoils, the chord line and the zero lift line are the same.Clancy, L.J., ''Aerodynamics'', paragraph 5.7(a) See also * Angle of attack * Aerobatics * Aerobatic maneuver References *Anderson, John D. Jr (2005), ''Introduction to Flight'', Section 7.4 (fifth edition), McGraw-Hill *L. J. Clancy Laurence Joseph Clancy (15 March 1929 - ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerodynamic Drag
In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers (or surfaces) or between a fluid and a solid surface. Unlike other resistive forces, such as dry friction, which are nearly independent of velocity, the drag force depends on velocity. Drag force is proportional to the velocity for low-speed flow and the squared velocity for high speed flow, where the distinction between low and high speed is measured by the Reynolds number. Even though the ultimate cause of drag is viscous friction, turbulent drag is independent of viscosity. Drag forces always tend to decrease fluid velocity relative to the solid object in the fluid's path. Examples Examples of drag include the component of the net aerodynamic or hydrodynamic force acting opposite to the di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chord (aircraft)
In aeronautics, the chord is an imaginary straight line joining the leading edge and trailing edge of an aerofoil. The chord length is the distance between the trailing edge and the point where the chord intersects the leading edge.L. J. Clancy (1975), ''Aerodynamics'', Section 5.2, Pitman Publishing Limited, London. The point on the leading edge used to define the chord may be the surface point of minimum radius. p.18 For a turbine aerofoil the chord may be defined by the line between points where the front and rear of a 2-dimensional blade section would touch a flat surface when laid convex-side up. The wing, horizontal stabilizer, vertical stabilizer and propeller/rotor blades of an aircraft are all based on aerofoil sections, and the term ''chord'' or ''chord length'' is also used to describe their width. The chord of a wing, stabilizer and propeller is determined by measuring the distance between leading and trailing edges in the direction of the airflow. (If a wing has ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NACA Airfoil
The NACA airfoils are airfoil shapes for aircraft wings developed by the National Advisory Committee for Aeronautics (NACA). The shape of the NACA airfoils is described using a series of digits following the word "NACA". The parameters in the numerical code can be entered into equations to precisely generate the cross-section of the airfoil and calculate its properties. Origins NACA initially developed the numbered airfoil system which was further refined by the United States Air Force at Langley Research Center. According to the NASA website: Four-digit series The NACA four-digit wing sections define the profile by: # First digit describing maximum camber as percentage of the chord. # Second digit describing the distance of maximum camber from the airfoil leading edge in tenths of the chord. # Last two digits describing maximum thickness of the airfoil as percent of the chord. For example, the NACA 2412 airfoil has a maximum camber of 2% located 40% (0.4 chords) from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nondimensionalization
Nondimensionalization is the partial or full removal of physical dimensions from an equation involving physical quantities by a suitable substitution of variables. This technique can simplify and parameterize problems where measured units are involved. It is closely related to dimensional analysis. In some physical systems, the term scaling is used interchangeably with ''nondimensionalization'', in order to suggest that certain quantities are better measured relative to some appropriate unit. These units refer to quantities intrinsic to the system, rather than units such as SI units. Nondimensionalization is not the same as converting extensive quantities in an equation to intensive quantities, since the latter procedure results in variables that still carry units. Nondimensionalization can also recover characteristic properties of a system. For example, if a system has an intrinsic resonance frequency, length, or time constant, nondimensionalization can recover these val ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerodynamic Center
In aerodynamics, the torques or moments acting on an airfoil moving through a fluid can be accounted for by the net lift and net drag applied at some point on the airfoil, and a separate net pitching moment about that point whose magnitude varies with the choice of where the lift is chosen to be applied. The aerodynamic center is the point at which the pitching moment coefficient for the airfoil does not vary with lift coefficient (i.e. angle of attack), making analysis simpler. : =0 where C_L is the aircraft lift coefficient. The lift and drag forces can be applied at a single point, the center of pressure, about which they exert zero torque. However, the location of the center of pressure moves significantly with a change in angle of attack and is thus impractical for aerodynamic analysis. Instead the aerodynamic center is used and as a result the incremental lift and drag due to change in angle of attack acting at this point is sufficient to describe the aerodynamic fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moment (physics)
In physics, a moment is a mathematical expression involving the product of a distance and physical quantity. Moments are usually defined with respect to a fixed reference point and refer to physical quantities located some distance from the reference point. In this way, the moment accounts for the quantity's location or arrangement. For example, the moment of force, often called torque, is the product of a force on an object and the distance from the reference point to the object. In principle, any physical quantity can be multiplied by a distance to produce a moment. Commonly used quantities include forces, masses, and electric charge distributions. Elaboration In its most basic form, a moment is the product of the distance to a point, raised to a power, and a physical quantity (such as force or electrical charge) at that point: : \mu_n = r^n\,Q, where Q is the physical quantity such as a force applied at a point, or a point charge, or a point mass, etc. If the quantity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tailless Aircraft
In aeronautics, a tailless aircraft is an aircraft with no other horizontal aerodynamic surface besides its main wing. It may still have a fuselage, vertical tail fin (vertical stabilizer), and/or vertical rudder. Theoretical advantages of the tailless configuration include low parasitic drag as on the Horten H.IV soaring glider and good stealth characteristics as on the Northrop B-2 Spirit bomber. Disadvantages include a potential sensitivity to trim. Tailless aircraft have been flown since the pioneer days; the first stable aeroplane to fly was the tailless Dunne D.5, in 1910. The most successful tailless configuration has been the tailless delta, especially for combat aircraft, though the most familiar tailless delta is the Concorde airliner. NASA has used the 'tailless' description for the novel X-36 research aircraft which has a canard foreplane but no vertical fin. Aircraft configuration A tailless aircraft has no other horizontal surface besides its main wing. The aer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflex Camber Line
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs via neural pathways in the nervous system called reflex arcs. A stimulus initiates a neural signal, which is carried to a synapse. The signal is then transferred across the synapse to a motor neuron which evokes a target response. These neural signals do not always travel to the brain, so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought. Many reflexes are fine-tuned to increase organism survival and self-defense. This is observed in reflexes such as the startle reflex, which provides an automatic response to an unexpected stimuli, and the feline righting reflex, which reorients a cat's body when falling to ensure safe landing. The simplest type of reflex, a short-latency reflex, has a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave Drag
In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (resting) value at some frequency. When the entire waveform moves in one direction, it is said to be a ''traveling wave''; by contrast, a pair of superimposed periodic waves traveling in opposite directions makes a ''standing wave''. In a standing wave, the amplitude of vibration has nulls at some positions where the wave amplitude appears smaller or even zero. Waves are often described by a ''wave equation'' (standing wave field of two opposite waves) or a one-way wave equation for single wave propagation in a defined direction. Two types of waves are most commonly studied in classical physics. In a ''mechanical wave'', stress and strain fields oscillate about a mechanical equilibrium. A mechanical wave is a local deformation (strain) in s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
