A vortex is created by the passage of an aircraft wing, revealed by smoke. Vortices are one of the many phenomena associated with the study of aerodynamics. The vortex is created by the difference in pressure between the upper and lower surface of the wing. The high pressure air below the lower surface of the wing moves around the wingtip towards the lower-pressure region on the upper surface, creating the vortex.

Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a solid object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with the difference being that gas dynamics applies to all gases.

Overview[link]

Understanding 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 spatial position and time. Aerodynamics allows the definition and solution of equations for the conservation of mass, momentum, and energy in air. The use of aerodynamics through mathematical analysis, empirical approximations, wind tunnel experimentation, and computer simulations form the scientific basis for heavier-than-air flight and a number of other technologies.

Aerodynamic problems can be classified according to the flow environment. External aerodynamics is the study of flow around solid objects of various shapes. Evaluating the lift and drag on an airplane or the shock waves that form in front of the nose of a rocket are examples of external aerodynamics. 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.

Aerodynamic problems can also be classified according to whether the flow speed is below, near or above the speed of sound. 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. Aerodynamicists disagree over the precise definition of hypersonic flow; minimum Mach numbers for hypersonic flow range from 3 to 12.

The influence of viscosity in the flow dictates a third classification. Some problems may encounter only very small viscous effects on the solution, in which case viscosity can be considered to be negligible. The approximations to these problems are called inviscid flows. Flows for which viscosity cannot be neglected are called viscous flows.

History[link]

Early ideas – ancient times to the 17th century[link]

A drawing of a design for a flying machine by Leonardo da Vinci (c. 1488). This machine was an ornithopter, with flapping wings similar to those of a bird, first presented in his Codex on the Flight of Birds in 1505.

Humans have been harnessing aerodynamic forces for thousands of years with sailboats and windmills.^[1] Images and stories of flight have appeared throughout recorded history,^[2] such as the legendary story of Icarus and Daedalus.^[3] Although observations of some aerodynamic effects such as wind resistance (e.g. drag) were recorded by Aristotle, Leonardo da Vinci and Galileo Galilei, very little effort was made to develop a rigorous quantitative theory of air flow prior to the 17th century.

In 1505, Leonardo da Vinci wrote the Codex on the Flight of Birds, one of the earliest treatises on aerodynamics. He notes for the first time that the center of gravity of a flying bird does not coincide with its center of pressure, and he describes the construction of an ornithopter, with flapping wings similar to a bird's.

Sir Isaac Newton was the first person to develop a theory of air resistance,^[4] making him one of the first aerodynamicists. As part of that theory, Newton considered that drag was due to the dimensions of a body, the density of the fluid, and the velocity raised to the second power. These 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 was expressed as Failed to parse (Missing texvc executable; please see math/README to configure.): F = \rho SV^2 \sin^2 (\theta)

This equation is incorrect for the calculation of drag in most cases. Drag on a flat plate is closer to being linear with the angle of inclination as opposed to acting quadratically at low angles. The Newton formula can lead one to believe that flight is more difficult than it actually is, due to this overprediction of drag and thus required thrust, and it may have contributed to a delay in human flight. However, it is more correct for a very slender plate when the angle becomes large and flow separation occurs, or if the flow speed is supersonic.^[5]

Modern beginnings – 18th to 19th century[link]

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

In 1738 The Dutch-Swiss mathematician Daniel Bernoulli published Hydrodynamica, in which he described the fundamental relationship among pressure, density, and velocity; in particular Bernoulli's principle, which is one method to calculate aerodynamic lift.^[6] More general equations of fluid flow - the Euler equations - were published by Leonhard Euler in 1757. The Euler equations were extended to incorporate the effects of viscosity in the first half of the 1800s, resulting in the Navier-Stokes equations.

Sir George Cayley is credited as the first person to identify the four aerodynamic forces of flight—weight, lift, drag, and thrust—and the relationships between them.^[7][8] 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. Among the shapes he investigated were the cross-sections of trout. 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.

Air resistance experiments were carried out by investigators throughout the 18th and 19th centuries. Drag theories were developed by Jean le Rond d'Alembert,^[9] Gustav Kirchhoff,^[10] and Lord Rayleigh.^[11] Equations for fluid flow with friction were developed by Claude-Louis Navier^[12] and George Gabriel Stokes.^[13] 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.

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. Wenham was also a member of the first professional organization dedicated to aeronautics, the Royal Aeronautical Society of the United Kingdom. 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 Osborne Reynolds.^[14] Reynolds also experimented with laminar to turbulent flow transition in 1883.

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.

A replica of the Wright Brothers' wind tunnel is on display at the Virginia Air and Space Center. 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.^[15] Renard and German physicist Hermann von Helmholtz explored the wing loading (weight to wing-area ratio) 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. 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.^[16]

Practical flight – early 20th century[link]

With the information contained in Chanute's book, the personal assistance of Chanute himself, and research carried out in their own wind tunnel, the Wright brothers gained enough knowledge of aerodynamics to fly the first powered aircraft on December 17, 1903. The Wright brothers' flight confirmed or disproved a number of aerodynamics theories. Newton's drag force theory was finally proved incorrect. This first widely-publicised 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,^[17] Martin Wilhelm Kutta, and Nikolai Zhukovsky independently created theories that connected circulation of a fluid flow to lift. 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^[18] behind thin-airfoil and lifting-line theories as well as work with boundary layers. Prandtl, a professor at the University of Göttingen, instructed many students who would play important roles in the development of aerodynamics, such as Theodore von Kármán and Max Munk.

Design issues with increasing speed[link]

Compressibility is an important factor in aerodynamics. At low speeds, the compressibility of air is not significant in relation to aircraft design, but as the airflow nears and exceeds the speed of sound, a host of new aerodynamic effects become important in the design of aircraft. These effects, often several of them at a time, made it very difficult for World War II era aircraft to reach speeds much beyond 800 km/h (500 mph).

Some of the minor effects include changes to the airflow that lead to problems in control. For instance, the P-38 Lightning with its thick high-lift wing had a particular problem in high-speed dives that led to a nose-down condition. Pilots would enter dives, and then find that they could no longer control the plane, which continued to nose over until it crashed. The problem was remedied by adding a "dive flap" beneath the wing which altered the center of pressure distribution so that the wing would not lose its lift.^[19]

A similar problem affected some models of the Supermarine Spitfire. At high speeds the ailerons could apply more torque than the Spitfire's thin wings could handle, and the entire wing would twist in the opposite direction. This meant that the plane would roll in the direction opposite to that which the pilot intended, and led to a number of accidents. Earlier models weren't fast enough for this to be a problem, and so it wasn't noticed until later model Spitfires like the Mk.IX started to appear. This was mitigated by adding considerable torsional rigidity to the wings, and was wholly cured when the Mk.XIV was introduced.

The Messerschmitt Bf 109 and Mitsubishi Zero had the exact opposite problem in which the controls became ineffective. At higher speeds the pilot simply couldn't move the controls because there was too much airflow over the control surfaces. The planes would become difficult to maneuver, and at high enough speeds aircraft without this problem could out-turn them.

These problems were eventually solved as jet aircraft reached transonic and supersonic speeds. German scientists in WWII experimented with swept wings. Their research was applied on the MiG-15 and F-86 Sabre and bombers such as the B-47 Stratojet used swept wings which delay the onset of shock waves and reduce drag. The all-flying tailplane which are common on supersonic planes also help maintain control near the speed of sound.

Finally, another common problem that fits into this category is flutter. At some speeds the airflow over the control surfaces will become turbulent, and the controls will start to flutter. If the speed of the fluttering is close to a harmonic of the control's movement, the resonance could break the control off completely. This was a serious problem on the Zero. When problems with poor control at high speed were first encountered, they were addressed by designing a new style of control surface with more power. However this introduced a new resonant mode, and a number of planes were lost before this was discovered.

All of these effects are often mentioned in conjunction with the term "compressibility", but in a manner of speaking, they are incorrectly used. From a strictly aerodynamic point of view, the term should refer only to those side-effects arising as a result of the changes in airflow from an incompressible fluid (similar in effect to water) to a compressible fluid (acting as a gas) as the speed of sound is approached. There are two effects in particular, wave drag and critical mach.

Wave drag is a sudden rise in drag on the aircraft, caused by air building up in front of it. At lower speeds this air has time to "get out of the way", guided by the air in front of it that is in contact with the aircraft. But at the speed of sound this can no longer happen, and the air which was previously following the streamline around the aircraft now hits it directly. The amount of power needed to overcome this effect is considerable. The critical mach is the speed at which some of the air passing over the aircraft's wing becomes supersonic.

At the speed of sound the way that lift is generated changes dramatically, from being dominated by Bernoulli's principle to forces generated by shock waves. Since the air on the top of the wing is traveling faster than on the bottom, due to Bernoulli effect, at speeds close to the speed of sound the air on the top of the wing will be accelerated to supersonic. When this happens the distribution of lift changes dramatically, typically causing a powerful nose-down trim. Since the aircraft normally approached these speeds only in a dive, pilots would report the aircraft attempting to nose over into the ground.

Dissociation absorbs a great deal of energy in a reversible process. This greatly reduces the thermodynamic temperature of hypersonic gas decelerated near an aerospace vehicle. In transition regions, where this pressure dependent dissociation is incomplete, both the differential, constant pressure heat capacity and beta (the volume/pressure differential ratio) will greatly increase. The latter has a pronounced effect on vehicle aerodynamics including stability.

Faster than sound – later 20th century[link]

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. In compressible aerodynamics, density and pressure both change, which is the basis for calculating the speed of sound. 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. 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. William John Macquorn Rankine and Pierre Henri Hugoniot independently developed the theory for flow properties before and after a shock wave. Jakob Ackeret led the initial work on calculating the lift and drag on a supersonic airfoil.^[20] Theodore von Kármán and Hugh Latimer Dryden introduced the term transonic to describe flow speeds around Mach 1 where drag increases rapidly. Because of the increase in drag approaching Mach 1, aerodynamicists and aviators disagreed on whether supersonic flight was achievable.

Image showing shock waves from NASA's X-43A hypersonic research vehicle in flight at Mach 7, generated using a computational fluid dynamics algorithm.

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.^[21] Participants included Theodore von Kármán, Ludwig Prandtl, Jakob Ackeret, Eastman Jacobs, Adolf Busemann, Geoffrey Ingram Taylor, Gaetano Arturo Crocco, and Enrico Pistolesi. Ackeret presented a design for a supersonic wind tunnel. Busemann gave a presentation on the need for aircraft with swept wings for high speed flight. 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. 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.

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. 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, with wind-tunnel tests followed by flight tests to confirm the computer predictions.

With some exceptions, the knowledge of hypersonic aerodynamics has matured between the 1960s and the present decade. 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. 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. Nevertheless, there are still important problems in basic aerodynamic theory, such as in predicting transition to turbulence, and the existence and uniqueness of solutions to the Navier-Stokes equations.

Introductory terminology[link]

• Lift
• Drag
• Reynolds number
• Mach number

Continuity assumption[link]

The foundation of aerodynamic prediction is the continuity assumption. In reality, gases are composed of molecules which collide with one another and solid objects. To derive the equations of aerodynamics, fluid properties such as density and velocity are assumed to be well-defined at infinitely small points, and to vary continuously from one point to another. That is, 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 continuous aerodynamics. The Knudsen number can be used to guide the choice between statistical mechanics and the continuous formulation of aerodynamics.

Laws of conservation[link]

Aerodynamic problems are normally solved using conservation laws as applied to a fluid continuum. The conservation laws can be written in integral or differential form. In many basic problems, three conservation principles are used:

• Continuity: If a certain mass of fluid enters a volume, it must either exit the volume or change the mass inside the volume. In fluid dynamics, the continuity equation is analogous to Kirchhoff's Current Law in electric circuits. The differential form of the continuity equation is:

Failed to parse (Missing texvc executable; please see math/README to configure.): \ {\partial \rho \over \partial t} + \nabla \cdot (\rho \mathbf{u}) = 0.

Above, Failed to parse (Missing texvc executable; please see math/README to configure.): \rho

is the fluid density, u is a velocity vector, and t is time. Physically, the equation also shows that mass is neither created nor destroyed in the control volume.[22] For a steady state process, the rate at which mass enters the volume is equal to the rate at which it leaves the volume.[23] Consequently, the first term on the left is then equal to zero. For flow through a tube with one inlet (state 1) and exit (state 2) as shown in the figure in this section, the continuity equation may be written and solved as:

Failed to parse (Missing texvc executable; please see math/README to configure.): \ \rho_{1} u_{1} A_{1} = \rho_{2} u_{2} A_{2}.

Above, A is the variable cross-section area of the tube at the inlet and exit. For incompressible flows, density remains constant.

• Conservation of Momentum: This equation applies Newton's second law of motion to a continuum, whereby force is equal to the time derivative of momentum. Both surface and body forces are accounted for in this equation. For instance, F could be expanded into an expression for the frictional force acting on an internal flow.

Failed to parse (Missing texvc executable; please see math/README to configure.): \ {D \mathbf{u} \over D t} = \mathbf{F} - {\nabla p \over \rho}

For the same figure, a control volume analysis yields:

Failed to parse (Missing texvc executable; please see math/README to configure.): \ p_{1}A_{1} + \rho_{1}A_{1}u_{1}^2 + F = p_{2}A_{2} + \rho_{2}A_{2}u_{2}^2.

Above, the force Failed to parse (Missing texvc executable; please see math/README to configure.): F

is placed on the left side of the equation, assuming it acts with the flow moving in a left-to-right direction. Depending on the other properties of the flow, the resulting force could be negative which means it acts in the opposite direction as depicted in the figure. In aerodynamics, air is normally assumed to be a Newtonian fluid, which posits a linear relationship between the shear stress (the internal friction forces) and the rate of strain of the fluid. The equation above is a vector equation: in a three dimensional flow, it can be expressed as three scalar equations. The conservation of momentum equations are often called the Navier-Stokes equations, while others use the term for the system that includes conversation of mass, conservation of momentum, and conservation of energy.

• Conservation of Energy: Although energy can be converted from one form to another, the total energy in a given closed system remains constant.

Failed to parse (Missing texvc executable; please see math/README to configure.): \ \rho {Dh \over Dt} = {D p \over D t} + \nabla \cdot \left( k \nabla T\right) + \Phi

Above, h is enthalpy, k is the thermal conductivity of the fluid, T is temperature, and Failed to parse (Missing texvc executable; please see math/README to configure.): \Phi

is the viscous dissipation function. The viscous dissipation function governs the rate at which mechanical energy of the flow is converted to heat. The term is always positive since, according to the second law of thermodynamics, viscosity cannot add energy to the control volume.[24] The expression on the left side is a material derivative. Again using the figure, the energy equation in terms of the control volume may be written as:

Failed to parse (Missing texvc executable; please see math/README to configure.): \ \rho_{1}u_{1}A_{1} \left( h_{1} + {u_{1}^{2} \over 2}\right) + \dot{W} + \dot{Q} = \rho_{2}u_{2}A_{2} \left( h_{2} + {u_{2}^{2} \over 2}\right).

Above, the shaft work Failed to parse (Missing texvc executable; please see math/README to configure.): \dot{W}

and heat transfer Failed to parse (Missing texvc executable; please see math/README to configure.): \dot{Q}
are assumed to be acting on the flow. They may be positive (to the flow from the surroundings) or negative (to the surroundings from the flow) depending on the problem. 

The ideal gas law or another equation of state is often used in conjunction with these equations to form a determined system to solve for the unknown variables.

Incompressible aerodynamics[link]

An incompressible flow is characterized by a constant density despite flowing over surfaces or inside ducts. While all real fluids are compressible, a flow problem is often considered incompressible if the density changes in the problem have a small effect on the outputs of interest. This is more likely to be true when the flow speeds are significantly lower than the speed of sound. For higher speeds, the flow will compress more significantly as it comes into contact with surfaces and slows. The Mach number is used to evaluate whether the incompressibility can be assumed or the flow must be solved as compressible.

Subsonic flow[link]

Subsonic (or low-speed) aerodynamics is the study of fluid motion which is everywhere much slower than the speed of sound through the fluid or gas. There are several branches of subsonic flow but one special case arises when the flow is inviscid, incompressible and irrotational. This case is called Potential flow and allows the differential equations used to be a simplified version of the governing equations of fluid dynamics, thus making available to the aerodynamicist a range of quick and easy solutions.^[25]

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. 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 0.3 (about 335 feet (102m) per second or 228 miles (366 km) per hour at 60 °F). Above 0.3, the problem should be solved by using compressible aerodynamics.

Compressible aerodynamics[link]

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. 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 0.3. 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[link]

The term Transonic refers to a range of velocities just below and above the local speed of sound (generally taken as Mach 0.8–1.2). 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. Between these speeds some of the airflow is supersonic, and some is not.

Supersonic flow[link]

Supersonic aerodynamic problems are those involving flow speeds greater than the speed of sound. Calculating the lift on the Concorde during cruise can be an example of a supersonic aerodynamic problem.

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. 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 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. 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.

Hypersonic flow[link]

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[link]

Different types flow analysis around an airfoil:

  Potential flow theory

  Boundary layer flow theory

  Turbulent wake analysis

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

Boundary layers[link]

The concept of a boundary layer is important in many aerodynamic problems. 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[link]

In aerodynamics, turbulence is characterized by chaotic, stochastic property changes in the flow. 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[link]

Aerodynamics is important in a number of applications other than aerospace engineering. It is a significant factor in any type of vehicle design, including automobiles. It is important in the prediction of forces and moments in sailing. It is used in the design of mechanical components such as hard drive heads. Structural engineers also use aerodynamics, and particularly aeroelasticity, to calculate wind loads in the design of large buildings and bridges. 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. 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.

See also[link]

References[link]

Further reading[link]

External links[link]

Wikimedia Commons has media related to: Aerodynamics

• NASA Beginner's Guide to Aerodynamics
• Smithsonian National Air and Space Museum's How Things Fly website
• Aerodynamics for Students
• Applied Aerodynamics: A Digital Textbook
• Aerodynamics for Pilots
• Aerodynamics and Race Car Tuning
• Aerodynamic Related Projects
• eFluids Bicycle Aerodynamics
• Application of Aerodynamics in Formula One (F1)
• Aerodynamics in Car Racing
• Aerodynamics of Birds
• Aerodynamics and dragonfly wings

Martin Brundle Brundle in 2004 Born (1959-06-01) 1 June 1959 (age 53) Formula One World Championship career Nationality British Active years 1984–1989, 1991–1996 Teams Tyrrell, Zakspeed, Williams, Brabham, Benetton, Ligier, McLaren and Jordan Races 165 (158 starts) Championships 0 Wins 0 Podiums 9 Career points 98 Pole positions 0 Fastest laps 0 First race 1984 Brazilian Grand Prix Last race 1996 Japanese Grand Prix

24 Hours of Le Mans career Participating years 1987–1988, 1990, 1997–1999, 2001 Teams Jaguar Nissan Motorsport Toyota Team Europe Team Bentley Best finish 1st (1990) Class wins 1 (1990)

Martin John Brundle (born 1 June 1959 in King's Lynn, Norfolk) is a British racing driver from England, known as a Formula One driver and as an F1 commentator for ITV Sport from 1997 to 2008, the BBC from 2009 to 2011 and Sky Sports from 2012.^[1]

Brundle contested the British Formula Three Championship with Ayrton Senna in 1983, finishing a close second, and the two progressed to Formula One the next year. Brundle failed to score a victory at the top level of single seaters, but he has been very successful in other disciplines. He was the 1988 World Sportscar Champion, with a record points haul, and won the 1990 Le Mans 24 hour Race for Jaguar in an XJR-12.

Career[link]

Early racing career[link]

Brundle had an unorthodox route to Formula One.^[2] He began his racing career at the age of 12, competing in grass track racing,^[3] in the Norfolk village of Pott Row.^[2] In 1975, he moved to Hot Rod racing and received 'Star grade' status. In 1979, he started single seaters with Formula Ford. During this time, he also raced Tom Walkinshaw's BMW race cars, achieving second against a field of international drivers at Snetterton. He won the BMW championship in 1980 and partnered Sir Stirling Moss in the BP/Audi team of 1981. In 1982, he moved up to Formula 3 achieving five poles and two wins in his debut season. He won the Grovewood Award as the most promising Commonwealth driver.^[3] The next year, he battled Ayrton Senna for the F3 championship, which Brundle eventually lost on the final laps of the last race.^[4] In 1984, he was promoted to Formula One.

Formula One (1984–1987)[link]

His Formula One career began with Tyrrell in 1984.^[5] He put in a number of aggressive and fast drives, finishing fifth in his first race at Brazil and then second at Detroit.^[5] At the Dallas Grand Prix, Brundle broke his ankles and both feet in a crash ^[4] during a practice session. Then Tyrrell were disqualified from the world championship in 1984 because of a technical infringement, wiping his achievements for that season from the record books.

For the next two seasons he remained with Tyrrell, but without a works engine supply the team struggled against the works engine teams. In 1987 he switched to Zakspeed, but managed only two points, the car unable to compete with the frontrunners. These two points were the only ones in the team's history.

Brundle at the 1990 IMSA Del Mar Grand Prix.

Sportscars and Brabham (1988–1991)[link]

Brundle started his famous link with Jaguar in 1982, driving touring cars.^[4] Four years of F1 racing for underfunded teams led him to seek a new challenge, and thus he took a year out and competed in the 1988 World Sportscar Championship and won the world sports car title,^[6] with a record points haul. He also won the Daytona 24 Hours the same year, for Jaguar. He became the test driver for Williams and stood in for Nigel Mansell at the 1988 Belgian Grand Prix,^[6] after Mansell was struck down with chickenpox.

In 1989 he returned to F1 full-time with the returning Brabham squad, but the former champions were unable to recapture their early 1980s success and Brundle opted to move back into the sports car arena for 1990. The Le Mans victory came that year and rejuvenated his career, but still a top-line race seat in Formula One eluded him. As well as contesting races in sports prototypes, Brundle also contested the American IROC series in 1990, taking a victory at the temporary circuit at Burke Lakefront Airport (the only IROC victory for a British driver) and coming 3rd in the overall standings. In 1991 he rejoined Brabham, but the squad had fallen even further down the grid and results were sparse.

Formula One (1992–1996)[link]

Seasoned observers noticed Brundle's drives into the points in the uncompetitive Brabham Yamaha in 1991, which was the last points finish for the Brabham team. This helped Brundle get a 1992 switch to Benetton, with whom he would finally claim a recognised podium finish and consistent points finishes with some gritty drives.

In 1992 he had a productive season, with a strong finish to the year. He came close to a win at Canada, where having overtaken Schumacher and closing on leader Gerhard Berger, the transmission failed.^[5] He never outqualified team-mate Michael Schumacher, but made up places with excellent starts (sixth to third at Silverstone), outraced the German at Imola, Montreal, Magny-Cours and Silverstone, and scored a notable second place at Monza. At Spa, Brundle went by when Schumacher went off the track. Schumacher noticed blisters on his team-mate's tyres on his return to the circuit and came in for slicks, a move that won him the race. Had Brundle not been distracted he would have pitted as planned at the end of that lap, with victory the most likely result. 1992 was his best F1 season,^[3] and is regarded in F1 as the closest any team mate came to matching Schumacher, prior to his 2010 comeback partnering Nico Rosberg.

To the shock of the F1 paddock,^[6] Brundle found himself dropped from Benetton for 1993, Italian Riccardo Patrese taking his place. He came very close to a seat with world champions Williams, but in the end Damon Hill got the drive instead. Still in demand within F1, Brundle raced for Ligier in 1993. More points finishes and a fine third at Imola were achieved in a car without active suspension. With finishing 7th in the World Drivers Championship behind the two Williams drivers Alain Prost (1st) and Damon Hill (3rd), McLaren team leader Ayrton Senna (2nd), the Benetton drivers Michael Schumacher (4th) and Riccardo Patrese (5th) and the Ferrari driver Jean Alesi (6th), Brundle was the most successful driver who did not have an active suspension system in his car and Ligier were the most successful team without an active suspension.

Brundle driving for Ligier at the 1995 British Grand Prix.

For 1994 Brundle was in the frame for the vacant McLaren seat alongside Mika Häkkinen. McLaren were hopeful of re-signing Alain Prost, who had retired at the end of 1993 after winning his fourth championship title, but decided not to renege on his retirement in March, and Brundle got the drive, beating out McLaren test driver Philippe Alliot. He was confirmed less than two weeks before the season-opening 1994 Brazilian Grand Prix.^[7]

Joining the team was a case of bad timing in many ways. McLaren were on a downturn and throughout 1994 were unable to win. The team's Peugeot engines were unreliable, as was to be expected from a debuting engine supplier. At Silverstone Brundle's engine appeared to explode just as the starting lights turned green. In reality the culprit was a clutch that cracked spilling its lubricants on top of the hot engine causing a spectacular fire. Nevertheless, when the car was reliable, Brundle put in strong performances that season, most notably at Monaco where he finished second to Schumacher.

Having had poor luck and with Mansell signed to McLaren for 1995, Brundle once more raced for Ligier that year, although not for the full season. To appease Mugen-Honda he had to share the second seat with Aguri Suzuki, a move denounced by many commentators and fans. He impressed however, a strong fourth at Magny-Cours and what would be his last F1 podium, at Spa, being the highlights. In 1996 he teamed up with Rubens Barrichello at Jordan and enjoyed a good season, despite a slow start and a spectacular crash at Melbourne's inaugural GP, with regular points, fourth his best result. He finished fifth in the 1996 Japanese Grand Prix, which was his last Grand Prix in Formula One.

Brundle achieved 9 podiums, and scored a total of 98 championship points, with a best championship finish of 6th in 1992. He was especially strong on street circuits and similarly slow-speed, twisty courses — Monaco, Adelaide and the Hungaroring each produced 4 points finishes for him.^[5] He holds the dubious distinction of having the longest Formula One career (158 Grand Prix starts) without a race victory, a pole position or a fastest lap.

Post Formula One[link]

Commentator[link]

Brundle's helmet on display in the Williams team's museum.

Brundle had hoped to stay in F1 beyond 1996, but could not find a seat. He was offered a seat at Sauber in 1997 following the dropping of Nicola Larini, but decided against it. Brundle did however return to Le Mans. Drives for Nissan, Toyota and Bentley impressed, but a second victory failed to materialise. Brundle's last Le Mans outing came in 2001, after which he focused on his role with the British Racing Drivers' Club (BRDC).

Having largely retired from motor racing, Brundle became a highly regarded commentator on British television network ITV, whom he joined when they began Formula One coverage in 1997, initially alongside Murray Walker, and from 2002 James Allen. Brundle joined the BBC's commentary team alongside Jonathan Legard when they won the rights to show F1 from 2009. Before the start of the 2011 season, the BBC announced that Brundle was being promoted to lead commentator and would be joined by fellow former F1 driver, David Coulthard.^[8] He signed for Sky Sports' coverage at the end of 2011 following the BBC's decision to relinquish their rights to show half of the following season's races live due to budgetary constraints.^[9]

For his television work Brundle has won the RTS Television Sports Award for best Sports Pundit in 1998, 1999, 2005 and 2006. In 2005 the judges described him as:

"...an outstanding operator at the very peak of his game – with an extraordinary ability to simplify and entertain in an often complex sport. He also exhibited a fearless authority on some of the most sensitive issues – not least his gimlet-eyed pursuit of Formula one boss Bernie Ecclestone on the grid at Indianapolis".^[10]

The production company responsible for ITV's F1 coverage, North One Television, also won the Sports Innovation Award for its Insight features, presented by Brundle. Discussing the return of Formula One to the BBC in 2009, The Times described Brundle "as the greatest TV analyst in this or any other sport."^[11]

Before becoming a regular commentator, Brundle was also part of the 1995 BBC commentary team whenever Aguri Suzuki was driving the Ligier-Mugen Honda, such as the 1995 San Marino Grand Prix.

With Steve Rider busy covering the England versus Kazakhstan 2010 FIFA World Cup Group 6 qualification match, Brundle co-commentated and presented coverage of the 2008 Japanese Grand Prix at Fuji Speedway.

Motorsport activities[link]

Brundle took the wheel of a Jaguar F1 car for the Formula One demonstration in London prior to the 2004 British Grand Prix and drove a BMW Sauber during a demonstration in 2006. Also in 2006, Brundle drove a 2005 Red Bull Racing car around Silverstone as part of ITV's 'F1 Insight' feature. This was followed up in 2007 with Brundle and colleague Blundell both driving Williams F1 cars to demonstrate overtaking.

In 2008 he came out of retirement to drive in the Formula Palmer Audi Championship alongside his son Alex, who was a series regular. He scored three top-eight finishes from the three races in which he took part.^[12] Alex will compete in the FIA Formula Two Championship for 2009.

Brundle came out of retirement again to race for United Autosports in the 2011 Daytona 24 Hours, sharing a Ford-powered Riley with Zak Brown, Mark Patterson and former Ligier and Brabham teammate Blundell; the team finished fourth overall.^[13]

In June 2011, shortly before the 2011 European Grand Prix, Brundle completed a one-off Formula One test for the series' tyre supplier Pirelli at Jerez. He completed a total of 70 laps on all of their tyre compounds, with the results and events of the day aired before the 2011 Hungarian Grand Prix.

Brundle is scheduled to return to Le Mans in 2012, teaming up with son Alex to race a Greaves Motorsport-run Zytek-Nissan LMP2. It will be his first appearance at the French classic in over a decade.^[14]

Other activities[link]

Brundle has also been involved in driver management. At present, he is David Coulthard's manager (as well as his former co-commentator). He also co-owned a management company, 2MB Sports Management, alongside Mark Blundell until January 2009, when he announced his intention to step down in order to focus on his television responsibilities and his son's career.^[15] Their clients include McLaren test driver Gary Paffett and British Formula Three champion Mike Conway.

Brundle also presented a documentary on British television in 1998 called Great Escapes, which showed generally live recordings, and occasionally reconstructions, of stories where human beings managed to somehow survive in face of various dangers or perils. It ran for one series on ITV.

In 2004 he released his first book Working the Wheel. The title is a reference to his 1996 crash in Melbourne.^{[citation needed]}

On Friday 13 February 2009, Brundle presented BBC Look East's 6.30pm bulletin, with Susie Fowler-Watt, reproducing his famous gridwalk.^[16]

Criticism of Max Mosley and the FIA[link]

In September 2007 he suggested that the treatment of McLaren "had the feel of a witch hunt" in his Sunday Times column.^[17] As a result of these comments Brundle and the Sunday Times received a French writ from Max Mosley and the FIA for libel. In the same column on December 9, 2007 he accused the FIA of double standards and of issuing the writ at the same time as clearing Renault of spying as a warning to other journalists:

The timing of the writ is significant, in my view, given the FIA’s decision to find Renault guilty of having significant McLaren designs and information within their systems, but not administering any penalty. It is a warning sign to other journalists and publications to choose their words carefully over that decision. I’m tired of what I perceive as the "spin" and tactics of the FIA press office, as are many other journalists. I expect my accreditation pass for next year will be hindered in some way to make my coverage of F1 more difficult and to punish me. Or they will write to ITV again to say that my commentary is not up to standard despite my unprecedented six Royal Television Society Awards for sports broadcasting. So be it.^[18]

Brundle also asserted his right to voice his opinion about Formula One:

As a former Formula One driver, I have earnt the right to have an opinion about the sport, and probably know as much about it as anybody else. I have attended approaching 400 grands prix, 158 as a driver. I have spilt blood, broken bones, shed tears, generated tanker loads of sweat, tasted the champagne glories and plumbed the depths of misery. I have never been more passionate about F1 and will always share my opinions in an honest and open way, knowing readers will make up their own minds.^[18]

In March 2008 Brundle voiced his opinion regarding the position of Max Mosley following the News of The World's allegation that Mosley had engaged in sexual acts with five prostitutes in a scenario that involved Nazi role-playing;^[19] saying "It's not appropriate behaviour for the head of any global body such as the FIA."^[20] In April Brundle argued:

"The specific detail of the scandal surrounding him is largely irrelevant, in my view. The sporting regulation he has used over the years to keep teams in check relates to bringing the sport into disrepute. If you live by the sword, you die by the sword. Sitting on the fence on this issue for any of us inside the sport is not an option. We must condone or condemn the situation he finds himself in. Mosley's position as president is untenable.^[21]

Pikey probe[link]

Brundle was the subject of 14 complaints to Ofcom and 22 to ITV, for using the term "pikeys" during ITV's coverage of the 2008 Canadian Grand Prix. In a live pre-race interview with Bernie Ecclestone, Brundle referred to 'pikeys' making repairs to the surface at turn 10 of the track by laying down fresh tarmac. ITV later apologised for the incident.

The word is considered insulting by the traveller community. The Oxford English Dictionary traced its use to 1837 by The Times, referring to "strangers harvesting in the Isle of Sheppey". Later that century it meant a "turnpike traveller" or vagabond. Latterly, it has become a derogatory term for Irish Travellers and Gypsies.^[22][23]

Brundle and ITV were later cleared by Ofcom, as Brundle was not aware of the racial or cultural implications of the word, and ITV did apologise and explain the situation to him.^[24]

Helmet[link]

Brundle's helmet was white with two red stripes and a blue stripe between the two red stripes (inspired by the British flag) from the chin to the back of the helmet. In 1996, there were added a golden ring (with either 'Bensons and Hedges' or 'Brundle' written) and a blue drawing resembling a B upside down.^[25]

Personal[link]

The son of a motor car dealer, he and his brother Robin took over the family car dealership from their father. The business closed in 2003 after losing the local Toyota and Peugeot franchises.^[26] Robin is also a racing driver, who today competes in historic racing events, and is managing director of Lola Cars.

Brundle is married to Liz ^[2] and they have a daughter, Charlie, and a son, Alex.^[27] Alex competed in 2006 in the Formula Palmer Audi Autumn Trophy .^[28] Brundle has always lived within a 5-mile radius of King's Lynn,^[2] and currently lives in Gayton, Norfolk.

Racing record[link]

Complete Formula One results[link]

(key)

¹ Tyrrell were disqualified from the entire world championship for 1984 due to a technical infringement.

Complete 24 Hours of Le Mans results[link]

Year	Class	No	Tyres	Car	Team	Co-Drivers	Laps	Pos.	Class Pos.
1987	C1	6	D	Jaguar XJR-8LM Jaguar 6.9L V12	Silk Cut Jaguar Tom Walkinshaw Racing	John Nielsen	231	DNF	DNF
1988	C1	1	D	Jaguar XJR-9LM Jaguar 7.0L V12	Silk Cut Jaguar Tom Walkinshaw Racing	John Nielsen Price Cobb	306	DNF	DNF
1990	C1	1	G	Jaguar XJR-12 Jaguar 7.0L V12	Silk Cut Jaguar Tom Walkinshaw Racing	Alain Ferté David Leslie	220	DNF	DNF
	C1	3	G	Jaguar XJR-12 Jaguar 7.0L V12	Silk Cut Jaguar Tom Walkinshaw Racing	John Nielsen Price Cobb	359	1st	1st
1997	GT1	21	B	Nissan R390 GT1 Nissan VRH35L 3.5L Turbo V8	Nissan Motorsport TWR	Jörg Müller Wayne Taylor	139	DNF	DNF
1998	GT1	28	M	Toyota GT-One Toyota R36V 3.6L Turbo V8	Toyota Motorsports Toyota Team Europe	Emmanuel Collard Eric Hélary	191	DNF	DNF
1999	LMGTP	1	M	Toyota GT-One Toyota R36V 3.6L Turbo V8	Toyota Motorsports Toyota Team Europe	Emmanuel Collard Vincenzo Sospiri	90	DNF	DNF
2001	LMGTP	7	D	Bentley EXP Speed 8 Bentley (Audi) 3.6L Turbo V8	Team Bentley	Stéphane Ortelli Guy Smith	56	DNF	DNF

References[link]

External links[link]

Wikimedia Commons has media related to: Martin Brundle

• Official Website
• Martin Brundle at itv.com
• Quotes as an ITV commentator
• Fan site