A vortex is created by the passage of an aircraft wing, revealed by colored smoke. V erification of the O rigins of R otation in T ornadoes Ex periment or VORTEX, is a field project that seeks to understand how a Vortices are one of the many phenomena associated to the study of aerodynamics. The equations of aerodynamics show that the vortex is created by the difference in pressure between the upper and lower surface of the wing. At the end of the wing, the higher pressure on the lower surface effectively tries to 'reach over' to the low pressure side, creating rotation and the vortex.

Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. In physics the term dynamics customarily refers to the time evolution of physical processes Aerodynamics is closely related to fluid dynamics and gas dynamics, with much theory shared between them. Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion Gas dynamics is a branch of dynamics concerned with studying the motion of gases Aerodynamics is often used synonymously with gas dynamics, with the difference being that gas dynamics applies to all gases. Understanding the motion of air (often called a flow field) around an object enables the calculation of forces and moments acting on the object. Typical properties calculated for a flow field include velocity, pressure, density and temperature as a function of position and time. In Physics, velocity is defined as the rate of change of Position. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature By defining a control volume around the flow field, equations for the conservation of mass, momentum, and energy can be defined and used to solve for the properties. In Fluid mechanics and Thermodynamics, a control volume is a mathematical abstraction employed in the process of creating Mathematical models The use of aerodynamics through mathematical analysis, empirical approximation and wind tunnel experimentation form the scientific basis for heavier-than-air flight.

Aerodynamic problems can be identified in a number of ways. The flow environment defines the first classification criterion. External aerodynamics is the study of flow around solid objects of various shapes. Evaluating the lift and drag on an airplane, the shock waves that form in front of the nose of a rocket or the flow of air over a hard drive head are examples of external aerodynamics. In the context of a Fluid flow relative to a body the lift force is the component of the Aerodynamic force that is Perpendicular to the flow In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a Overview Fixed-wing aircraft range from small training and recreational aircraft to Wide-body aircraft and military cargo aircraft. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called A rocket or rocket vehicle is a Missile, Aircraft or other Vehicle which obtains Thrust by the reaction of the Internal aerodynamics is the study of flow through passages in solid objects. For instance, internal aerodynamics encompasses the study of the airflow through a jet engine or through an air conditioning pipe. specific --->A jet engine is a Reaction engine that discharges a fast moving jet of Fluid to The term air conditioning refers to the cooling and dehumidification of indoor air for Thermal comfort.

The ratio of the problem's characteristic flow speed to the speed of sound comprises a second classification of aerodynamic problems. Sound is a vibration that travels through an elastic medium as a Wave. A problem is called subsonic if all the speeds in the problem are less than the speed of sound, transonic if speeds both below and above the speed of sound are present (normally when the characteristic speed is approximately the speed of sound), supersonic when the characteristic flow speed is greater than the speed of sound, and hypersonic when the flow speed is much greater than the speed of sound. Transonic is an Aeronautics term referring to a range of velocities just below and above the Speed of sound (about mach 0 For other uses see Supersonic. The term supersonic is used to define a speed that is over the Speed of sound ( Mach 1 In Aerodynamics, hypersonic speeds are speeds that are highly Supersonic. Aerodynamicists disagree over the precise definition of hypersonic flow; minimum Mach numbers for hypersonic flow range from 3 to 12. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid Most aerodynamicists use numbers between 5 and 8.

The influence of viscosity in the flow dictates a third classification. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. Some problems involve only negligible viscous effects on the solution, in which case viscosity can be considered to be nonexistent. The approximations to these problems are called inviscid flows. In Fluid dynamics there are problems that are easily solved by using the simplifying assumption of an ideal Fluid that has no Viscosity. Flows for which viscosity cannot be neglected are called viscous flows.

History

A drawing of a design for a flying machine by Leonardo da Vinci (c. Leonardo di ser Piero da Vinci ( April 15 1452 – May 2 1519 was an Italian Polymath, having been a scientist Mathematician, Engineer 1488). This machine was an ornithopter, with flapping wings similar to a bird, first appeared in his Codex on the Flight of Birds in 1505. Early history The idea of constructing wings in order to imitate the flight of birds dates to the ancient Greek legend of Daedalus and Icarus Codex on the Flight of Birds is a relatively short Codex of circa 1505 by Leonardo da Vinci.

Images and stories of flight have appeared throughout recorded history, with perhaps the most noted of these being the story of Icarus and Daedalus. Icarus ( Greek:, Latin: Íkaros, Etruscan: Vicare) is a character in Greek mythology. This article is about the mythological character For other uses see Daedalus (disambiguation. ^[1] Although observations of some aerodynamic effects like wind resistance (a. k. a. drag) were recorded by the likes of Aristotle and Galileo Galilei, very little effort was made to develop governing laws for understanding the nature of flight prior to the 17th century. In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. Galileo Galilei (15 February 1564 &ndash 8 January 1642 was a Tuscan ( Italian) Physicist, Mathematician, Astronomer, and Philosopher As a means of recording the passage of Time, the 17th Century was that Century which lasted from 1601 - 1700 in the Gregorian calendar

Sir Isaac Newton was the first person to develop a theory of air resistance,^[2] arguably making him the world's first aerodynamicist. Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements As part of that theory, Newton believed that drag was due to the dimensions of a body, the density of the fluid, and the velocity raised to the second power. These beliefs all turned out to be correct for low flow speeds. Newton also developed a law for the drag force on a flat plate inclined towards the direction of the fluid flow. Using F for the drag force, ρ for the density, S for the area of the flat plate, V for the flow velocity, and θ for the inclination angle, his law is expressed below.

Unfortunately, this equation is completely incorrect for the calculation of drag (unless the flow speed is hypersonic). In Aerodynamics, hypersonic speeds are speeds that are highly Supersonic. Drag on a flat plate is closer to being linear with the angle of inclination as opposed to acting quadratically. This formula can lead one to believe that flight is more difficult than it actually is, and it may have contributed to a delay in manned flight. ^[3]

A drawing of a glider by Sir George Cayley, one of the early attempts at creating an aerodynamic shape.

Sir George Cayley is credited as the first person to separate the forces of lift and drag which are in effect on any flight vehicle. Sir George Cayley 6th Baronet ( December 27, 1773 &ndash December 15, 1857) sometimes known as "the father of Aerodynamics" was In the context of a Fluid flow relative to a body the lift force is the component of the Aerodynamic force that is Perpendicular to the flow Cayley believed that the drag on a flying machine must be counteracted by a means of propulsion in order for level flight to occur. Cayley also looked to nature for aerodynamic shapes with low drag. One of the shapes he investigated were the cross-sections of trout. Trout is the common name given to a number of Species of Freshwater Fish belonging to the Salmonidae family This may appear counterintuitive, however, the bodies of fish are shaped to produce very low resistance as they travel through water. Their cross-sections are sometimes very close to that of modern low drag airfoils. An airfoil (in American English) or aerofoil (in British English) is the shape of a Wing or blade (of a Propeller, rotor

These empirical findings led to a variety of air resistance experiments on various shapes throughout the 18th and 19th centuries. The 18th century lasted from 1701 to 1800 in the Gregorian calendar, in accordance with the Anno Domini / Common Era numbering system The 19th century of the Common Era began on January 1, 1801 and ended on December 31, 1900, according to the Gregorian calendar Drag theories were developed by Jean le Rond d'Alembert,^[4] Gustav Kirchhoff,^[5] and Lord Rayleigh. Gustav Robert Kirchhoff ( March 12, 1824 &ndash October 17, 1887) was a German Physicist who contributed to the fundamental John William Strutt 3rd Baron Rayleigh OM (12 November 1842 &ndash 30 June 1919 was an English Physicist who with William Ramsay, discovered ^[6] Equations for fluid flow with friction were developed by Claude-Louis Navier^[7] and George Gabriel Stokes. Friction is the Force resisting the relative motion of two Surfaces in contact or a surface in contact with a fluid (e Claude-Louis Navier (10 February 1785 in Dijon – 21 August 1836 in Paris) born Claude Louis Marie Henri Navier (klod lwi maʁi ɑ̃ʁi naˈvje was a Sir George Gabriel Stokes 1st Baronet FRS ( 13 August 1819 &ndash 1 February 1903) was a mathematician and physicist ^[8] To simulate fluid flow, many experiments involved immersing objects in streams of water or simply dropping them off the top of a tall building. Towards the end of this time period Gustave Eiffel used his Eiffel Tower to assist in the drop testing of flat plates. Alexandre Gustave Eiffel ( December 15, 1832 &ndash December 27, 1923; in French efɛl in English usually ˈaɪfəl was a French The Eiffel Tower (Tour Eiffel /tuʀ ɛfɛl/ is an Iron Tower built

Of course, a more precise way to measure resistance is to place an object within an artificial, uniform stream of air where the velocity is known. The first person to experiment in this fashion was Francis Herbert Wenham, who in doing so constructed the first wind tunnel in 1871. A wind tunnel is a research tool developed to assist with studying the effects of air moving over or around solid objects Wenham was also a member of the first professional organization dedicated to aeronautics, the Royal Aeronautical Society of Great Britain. Founded in 1866 The Royal Aeronautical Society, also known as the RAeS, is a multidisciplinary professional institution dedicated to the entire global Aerospace See also Kingdom of Great Britain Great Britain (Breatainn Mhòr Prydain Fawr Breten Veur Graet Breetain is the larger of the two main islands Objects placed in wind tunnel models are almost always smaller than in practice, so a method was needed to relate small scale models to their real-life counterparts. This was achieved with the invention of the dimensionless Reynolds number by Osbourne Reynolds. In Fluid mechanics and Heat transfer, the Reynolds number \mathrm{Re} is a Dimensionless number that gives a measure of the Ratio Osborne Reynolds ( 23 August, 1842 &ndash 21 February, 1912) was a prominent innovator in the understanding of Fluid dynamics. ^[9] Reynolds also experimented with laminar to turbulent flow transition in 1883. Laminar flow, sometimes known as streamline flow occurs when a fluid flows in parallel layers with no disruption between the layers In Fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic Stochastic property changes

By the late 19th century, two problems were identified before heavier-than-air flight could be realized. The first was the creation of low-drag, high-lift aerodynamic wings. The second problem was how to determine the power needed for sustained flight. During this time, the groundwork was laid down for modern day fluid dynamics and aerodynamics, with other less scientifically inclined enthusiasts testing various flying machines with little success. Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion

A replica of the Wright Brothers' wind tunnel is on display at the Virginia Air and Space Center. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout A wind tunnel is a research tool developed to assist with studying the effects of air moving over or around solid objects Wind tunnels were key in the development and validation of the laws of aerodynamics.

In 1889, Charles Renard, a French aeronautical engineer, became the first person to reasonably predict the power needed for sustained flight. Charles Renard (Damblain Vosges, 1847 - Meudon 1905 French military engineer started to work after the Franco-Prussian War of 1870/71 on the design ^[10] Renard and German physicist Hermann von Helmholtz explored the wing loading of birds, eventually concluding that humans could not fly under their own power by attaching wings onto their arms. Otto Lilienthal, following the work of Sir George Cayley, was the first person to become highly successful with glider flights. Otto Lilienthal (born 23 May, 1848 in Anklam, Province of Pomerania &ndash died 10 August, 1896 in Berlin Lilienthal believed that thin, curved airfoils would produce high lift and low drag.

Octave Chanute provided a great service to those interested in aerodynamics and flying machines by publishing a book outlining all of the research conducted around the world up to 1893. Octave Chanute, (February 18 1832 &ndash November 23 1910 was a French-born American Railroad engineer and Aviation pioneer ^[11] With the information contained in that book and the personal assistance of Chanute himself, the Wright brothers had just enough knowledge of aerodynamics to fly the first manned aircraft on December 17, 1903, just in time to beat the efforts of Samuel Pierpont Langley. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Events 546 - Gothic War (535–554: The Ostrogoths of King Totila Year 1903 ( MCMIII) was a Common year starting on Thursday (link will display calendar of the Gregorian calendar or a Common year starting Samuel Pierpont Langley (August 22 1834 Roxbury Massachusetts &ndash February 27 1906 Aiken South Carolina) was an American Astronomer The Wright brothers' flight confirmed or disproved a number of aerodynamics theories. Newton's drag force theory was finally proved incorrect. The first flight led to a more organized effort between aviators and scientists, leading the way to modern aerodynamics.

During the time of the first flights, Frederick W. Lanchester,^[12] Martin Wilhelm Kutta, and Nikolai Zhukovsky independently created theories that connected circulation of a fluid flow to lift. Frederick William Lanchester, Hon FRAeS ( October 23, 1868 - March 8, 1946) was an English Polymath and Martin Wilhelm Kutta ( November 3, 1867 – December 25, 1944) was a German Mathematician. Nikolai Yegorovich Zhukovsky (Николай Егорович Жуковский ( &ndash March 17, 1921) was a Russian scientist founding father In Fluid dynamics, circulation is the Line integral around a closed curve of the Fluid Velocity. Kutta and Zhukovsky went on to develop a two-dimensional wing theory. Expanding upon the work of Lanchester, Ludwig Prandtl is credited with developing the mathematics^[13] behind thin-airfoil and lifting-line theories as well as work with boundary layers. Ludwig Prandtl ( 4 February 1875 &ndash 15 August 1953) was a German Physicist. In Physics and Fluid mechanics, a boundary layer is that layer of Fluid in the immediate vicinity of a bounding surface Prandtl, a professor at Gottingen University, instructed many students who would play important roles in the development of aerodynamics like Theodore von Kármán and Max Munk. The University of Göttingen ( German: Georg-August-Universität Göttingen) is a University in the city of Göttingen, Germany. Born in Germany about 1890 M Max Munk earned doctorates in both Physics and Mathematics from the University of Göttingen in 1917

As aircraft began to travel faster, aerodynamicists realized that the density of air began to change as it came into contact with an object, leading to a division of fluid flow into the incompressible and compressible regimes. A flow is considered to be a compressible flow if the change in Density of the flow with respect to Pressure is non-zero along a streamline. In compressible aerodynamics, density and pressure both change, which is the basis for calculating the speed of sound. Sound is a vibration that travels through an elastic medium as a Wave. Newton was the first to develop a mathematical model for calculating the speed of sound, but it was not correct until Pierre-Simon Laplace accounted for the molecular behavior of gases and introduced the heat capacity ratio. Ideal gas relations For an ideal gas the heat capacity is constant with temperature The ratio of the flow speed to the speed of sound was named the Mach number after Ernst Mach, who was one of the first to investigate the properties of supersonic flow which included Schlieren photography techniques to visualize the changes in density. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid Ernst Mach (max ( February 18, 1838 &ndash February 19, 1916) was an Austrian Physicist and Philosopher and For other uses see Supersonic. The term supersonic is used to define a speed that is over the Speed of sound ( Mach 1 Schlieren photography is a visual process that is used to photograph the flow of fluids of varying density William John Macquorn Rankine and Pierre Henri Hugoniot independently developed the theory for flow properties before and after a shock wave. William John Macquorn Rankine FRS ( July 5, 1820 &ndash December 24, 1872) was a Scottish engineer and Pierre-Henri Hugoniot (1851&ndash1887 was a French engineer who formulated the Rankine-Hugoniot equation. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called Jakob Ackeret led the initial work on calculating the lift and drag on a supersonic airfoil. Jakob Ackeret (1898-1981 was a Swiss Aeronautical engineer. He is widely viewed as one of the foremost aeronautics experts of 20th century ^[14] Theodore von Kármán and Hugh Latimer Dryden introduced the term transonic to describe flow speeds around Mach 1 where drag increases rapidly. Dr Hugh Latimer Dryden ( July 2, 1898 &ndash December 2, 1965) was an aeronautical Scientist and Civil servant Transonic is an Aeronautics term referring to a range of velocities just below and above the Speed of sound (about mach 0 Because of the increase in drag approaching Mach 1, aerodynamicists and aviators disagreed on whether manned supersonic flight was achievable.

A computer generated model of NASA's X-43A hypersonic research vehicle flying at Mach 7 using a computational fluid dynamics code. The X-43 is an unmanned experimental Hypersonic Aircraft design with multiple planned scale variations meant to test different Computational fluid dynamics (CFD is one of the branches of Fluid mechanics that uses Numerical methods and algorithms to solve and analyze problems that involve

On September 30, 1935 an exclusive conference was held in Rome with the topic of high velocity flight and the possibility of breaking the sound barrier. Events 1399 - Henry IV is proclaimed King of England. 1744 - France and Spain defeat the Year 1935 ( MCMXXXV) was a Common year starting on Tuesday (link will display full calendar of the Gregorian calendar. Rome ( Roma ˈroma Roma is the capital city of Italy and Lazio, and is Italy's largest and most populous city with more than 2 WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout ^[15] Participants included von Kármán, Prandtl, Ackeret, Eastman Jacobs, Adolf Busemann, Geoffrey Ingram Taylor, Gaetano Arturo Crocco, and Enrico Pistolesi. Eastman N Jacobs (1902&ndash1987 was a leading Aerodynamicist who worked for NACA 's Langley Research Center from the 1920s to the 1940s Adolph Busemann ( 20 April 1901 - 3 November 1986) was a German aerospace engineer and influential early pioneer in Sir Geoffrey Ingram Taylor OM ( 7 March 1886 - 27 June 1975) was a Physicist, Mathematician and expert on Fluid dynamics Gaetano Arturo Crocco (1877-1968 was the founder of the Italian Rocket Society and went on to become Italy 's leading space scientist The new research presented was impressive. Ackeret presented a design for a supersonic wind tunnel. A supersonic wind tunnel is a Wind tunnel that produces Supersonic speeds (1 Busemann gave perhaps the best presentation on the need for aircraft with swept wings for high speed flight. A swept-wing is a wing Planform common on high-speed Aircraft, with the wing swept back instead of being set at right angles to the Fuselage. Eastman Jacobs, working for NACA, presented his optimized airfoils for high subsonic speeds which led to some of the high performance American aircraft during World War II. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Supersonic propulsion was also discussed. The sound barrier was broken using the Bell X-1 aircraft twelve years later, thanks in part to those individuals. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

By the time the sound barrier was broken, much of the subsonic and low supersonic aerodynamics knowledge had matured. The Cold War fueled an ever evolving line of high performance aircraft. Cold War is the state of conflict tension and competition that existed between the United States and the Soviet Union (USSR and their respective allies from the Computational fluid dynamics was started as an effort to solve for flow properties around complex objects and has rapidly grown to the point where entire aircraft can be designed using a computer. Computational fluid dynamics (CFD is one of the branches of Fluid mechanics that uses Numerical methods and algorithms to solve and analyze problems that involve

With some exceptions, the knowledge of hypersonic aerodynamics has matured between the 1960s and the present decade. In Aerodynamics, hypersonic speeds are speeds that are highly Supersonic. Therefore, the goals of an aerodynamicist have shifted from understanding the behavior of fluid flow to understanding how to engineer a vehicle to interact appropriately with the fluid flow. For example, while the behavior of hypersonic flow is understood, building a scramjet aircraft to fly at hypersonic speeds has seen very limited success. A scramjet ( s upersonic c ombustion ramjet) is a variation of a Ramjet with the distinction being that some or all of the combustion process Along with building a successful scramjet aircraft, the desire to improve the aerodynamic efficiency of current aircraft and propulsion systems will continue to fuel new research in aerodynamics.

Introductory terminology

• Lift
• Drag
• Reynolds number
• Mach number

Continuity assumption

Gases are composed of molecules which collide with one another and solid objects. In the context of a Fluid flow relative to a body the lift force is the component of the Aerodynamic force that is Perpendicular to the flow In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a In Fluid mechanics and Heat transfer, the Reynolds number \mathrm{Re} is a Dimensionless number that gives a measure of the Ratio Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by If density and velocity are taken to be well-defined at infinitely small points, and are assumed to vary continuously from one point to another, the discrete molecular nature of a gas is ignored.

The continuity assumption becomes less valid as a gas becomes more rarefied. In these cases, statistical mechanics is a more valid method of solving the problem than aerodynamics. Statistical mechanics is the application of Probability theory, which includes mathematical tools for dealing with large populations to the field of Mechanics

Laws of Conservation

Aerodynamic problems are solved using the conservation laws, or equations derived from the conservation laws. In aerodynamics, three conservation laws are used:

• Conservation of mass: Matter is not created or destroyed. If a certain mass of fluid enters a volume, it must either exit the volume or increase the mass inside the volume. In a steady-state process mass cannot accumulate inside the volume and this law is expressed in the continuity equation. A continuity equation is a Differential equation that describes the conservative transport of some kind of quantity
• Conservation of momentum: Also called Newton's third law of motion. In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product Newton's laws of motion are three Physical laws which provide relationships between the Forces acting on a body and the motion of the The initial momentum (mass times velocity) of a system must equal the final momentum of the system. ^[16]
• Conservation of energy: Although it can be converted from one form to another, the total energy in a given system remains constant. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός

Incompressible aerodynamics

An incompressible flow is characterized by a constant density despite flowing over surfaces or inside ducts. A flow can be considered incompressible as long as its speed is low. For higher speeds, the flow will begin to compress as it comes into contact with surfaces. The Mach number is used to distinguish between incompressible and compressible flows. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid

Subsonic flow

Subsonic (or low-speed) aerodynamics is the study of inviscid, incompressible and irrotational aerodynamics where the differential equations used are a simplified version of the governing equations of fluid dynamics. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. In Thermodynamics and Fluid mechanics, compressibility is a measure of the relative volume change of a Fluid or Solid as a response In Vector calculus a conservative vector field is a Vector field which is the Gradient of a Scalar potential. A differential equation is a mathematical Equation for an unknown function of one or several variables that relates the values of the Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion ^[17]. It is a special case of Subsonic aerodynamics.

In solving a subsonic problem, one decision to be made by the aerodynamicist is whether to incorporate the effects of compressibility. Compressibility is a description of the amount of change of density in the problem. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different When the effects of compressibility on the solution are small, the aerodynamicist may choose to assume that density is constant. The problem is then an incompressible low-speed aerodynamics problem. When the density is allowed to vary, the problem is called a compressible problem. In air, compressibility effects are usually ignored when the Mach number in the flow does not exceed 0. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid 3 (about 335 feet per second or 228 miles per hour or 102 meters per second at 60^oF). Above 0. 3, the problem should be solved using compressible aerodynamics.

Compressible aerodynamics

Main article: Compressible flow

According to the theory of aerodynamics, a flow is considered to be compressible if its change in density with respect to pressure is non-zero along a streamline. A flow is considered to be a compressible flow if the change in Density of the flow with respect to Pressure is non-zero along a streamline. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface Fluid flow is described in general by a Vector field in three (for steady flows or four (for non-steady flows including time dimensions In short, this means that, unlike incompressible flow, changes in density must be considered. In general, this is the case where the Mach number in part or all of the flow exceeds 0. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid 3. The Mach . 3 value is rather arbitrary, but it is used because gas flows with a Mach number below that value demonstrate changes in density with respect to the change in pressure of less than 5%. Furthermore, that maximum 5% density change occurs at the stagnation point of an object immersed in the gas flow and the density changes around the rest of the object will be significantly lower. Transonic, supersonic, and hypersonic flows are all compressible.

Transonic flow

Main article: Transonic

The term Transonic refers to a range of velocities just below and above the local speed of sound (generally taken as Mach 0. Transonic is an Aeronautics term referring to a range of velocities just below and above the Speed of sound (about mach 0 Sound is a vibration that travels through an elastic medium as a Wave. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid 8–1. 2). It is defined as the range of speeds between the critical Mach number, when some parts of the airflow over an aircraft become supersonic, and a higher speed, typically near Mach 1.2, when all of the airflow is supersonic. The Critical Mach number (Mcr of an aircraft is the slowest Mach number at which the airflow over a small region of the wing reaches the speed of sound For other uses see Supersonic. The term supersonic is used to define a speed that is over the Speed of sound ( Mach 1 Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid Between these speeds some of the airflow is supersonic, and some is not.

Supersonic flow

Main article: Supersonic

Supersonic aerodynamic problems are those involving flow speeds greater than the speed of sound. For other uses see Supersonic. The term supersonic is used to define a speed that is over the Speed of sound ( Mach 1 Calculating the lift on the Concorde during cruise can be an example of a supersonic aerodynamic problem. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

Supersonic flow behaves very differently from subsonic flow. Fluids react to differences in pressure; pressure changes are how a fluid is "told" to respond to its environment. Therefore, since sound is in fact an infinitesimal pressure difference propagating through a fluid, the speed of sound in that fluid can be considered the fastest speed that "information" can travel in the flow. Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies Sound is a vibration that travels through an elastic medium as a Wave. This difference most obviously manifests itself in the case of a fluid striking an object. In front of that object, the fluid builds up a stagnation pressure as impact with the object brings the moving fluid to rest. In Fluid dynamics, stagnation pressure is the Pressure at a Stagnation point in a fluid flow where the kinetic energy is converted into pressure energy In fluid traveling at subsonic speed, this pressure disturbance can propagate upstream, changing the flow pattern ahead of the object and giving the impression that the fluid "knows" the object is there and is avoiding it. However, in a supersonic flow, the pressure disturbance cannot propagate upstream. Thus, when the fluid finally does strike the object, it is forced to change its properties -- temperature, density, pressure, and Mach number -- in an extremely violent and irreversible fashion called a shock wave. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid For articles on other forms of reversibility including reversibility of microscopic dynamics see Reversibility (disambiguation. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called The presence of shock waves, along with the compressibility effects of high-velocity (see Reynolds number) fluids, is the central difference between supersonic and subsonic aerodynamics problems. In Fluid mechanics and Heat transfer, the Reynolds number \mathrm{Re} is a Dimensionless number that gives a measure of the Ratio

Hypersonic flow

Main article: Hypersonic

In aerodynamics, hypersonic speeds are speeds that are highly supersonic. In Aerodynamics, hypersonic speeds are speeds that are highly Supersonic. In the 1970s, the term generally came to refer to speeds of Mach 5 (5 times the speed of sound) and above. The hypersonic regime is a subset of the supersonic regime. Hypersonic flow is characterized by high temperature flow behind a shock wave, viscous interaction, and chemical dissociation of gas.

Associated terminology

The incompressible and compressible flow regimes produce many associated phenomena, such as boundary layers and turbulence.

Boundary layers

Main article: Boundary layer

The concept of a boundary layer is important in many aerodynamic problems. In Physics and Fluid mechanics, a boundary layer is that layer of Fluid in the immediate vicinity of a bounding surface In Physics and Fluid mechanics, a boundary layer is that layer of Fluid in the immediate vicinity of a bounding surface The viscosity and fluid friction in the air is approximated as being significant only in this thin layer. This principle makes aerodynamics much more tractable mathematically.

Turbulence

Main article: Turbulence

In aerodynamics, turbulence is characterized by chaotic, stochastic property changes in the flow. In Fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic Stochastic property changes This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time. Flow that is not turbulent is called laminar flow.

Aerodynamics in other fields

Further information: Automotive aerodynamics

Aerodynamics is important in a number of applications other than aerospace engineering. Automotive aerodynamics is the study of the Aerodynamics of road vehicles It is a significant factor in any type of vehicle design, including automobiles. Modern automotive engineering is a branch of Vehicle engineering, incorporating elements of mechanical, electrical, electronic, software It is important in the prediction of forces and moments in sailing. Sailing is the art of controlling a Sailing vessel. By changing the Rigging, Rudder and dagger or centre board a Sailor manages the force It is used in the design of large components such as hard drive heads. A hard disk drive ( HDD) commonly referred to as a hard drive, hard disk, or fixed disk drive, is a Non-volatile storage device Structural engineers also use aerodynamics, and particularly aeroelasticity, to calculate wind loads in the design of large buildings and bridges. Structural engineering is a field of Engineering dealing with the analysis and design of Structures that support or resist loads Structural engineering is Aeroelasticity is the science which studies the interaction among inertial, elastic, and aerodynamic forces Wind is the flow of Air or other Gases that compose an Atmosphere (including but not limited to the Earth's) A bridge is a Structure built to span a Gorge, Valley, Road, railroad track, River, Body of water Urban aerodynamics seeks to help town planners and designers improve comfort in outdoor spaces, create urban microclimates and reduce the effects of urban pollution. The field of environmental aerodynamics studies the ways atmospheric circulation and flight mechanics affect ecosystems. Atmospheric circulation is the large-scale movement of air and the means (together with the smaller Ocean circulation) by which Heat is distributed on the surface The aerodynamics of internal passages is important in heating/ventilation, gas piping, and in automotive engines where detailed flow patterns strongly affect the performance of the engine. HVAC (pronounced either "H-V-A-C" or occasionally " H-vak " is an Initialism or Acronym that stands for " Heating Ducts are used in heating ventilation and air conditioning ( HVAC) to deliver and remove air The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a

See also

References

Further reading

External links

• NASA Beginner's Guide to Aerodynamics
• Aerodynamics for Students
• Applied Aerodynamics: A Digital Textbook
• Aerodynamics and Race Car Tuning
• Aerodynamic Related Projects
• Supersonic wing design
• eFluids Bicycle Aerodynamics
• Application of Aerodynamics in Formula One (F1)
• Aerodynamics in Car Racing
• Aerodynamics of Birds
• Aerodynamics and dragonfly wings