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134-495: The Citroën GS is a front-engine, front-drive, four or five door, five passenger family car manufactured and marketed by Citroën in two series: for model years 1970–1979 in fastback saloon and estate bodystyles and subsequently as the GSA for model years 1980–1986 in hatchback and estate body styles – the latter after a facelift . Combined production reached approximately 2.5 million. Noted for its aerodynamic body shape with

268-426: A shock wave . The presence of shock waves, along with the compressibility effects of high-flow velocity (see Reynolds number ) fluids, is the central difference between the supersonic and subsonic aerodynamics regimes. 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

402-504: A wind tunnel in the 1950s, helping them to create highly streamlined cars, like the DS, that were years ahead of their competitors, and so good were the aerodynamics of the CX model, that it took its name – c x {\displaystyle \mathbf {c} _{\mathrm {x} }\,} – from the mathematical term used to measure the drag coefficient. In the 1960s, Citroën undertook

536-464: A 1923 Citroën that had already travelled 48,000 km (30,000 mi) was the first car to be driven around Australia. The car, a 1923 Citroën 5CV Type C Torpedo, was driven by Neville Westwood from Perth , Western Australia , on a round trip from August to December 1925. This vehicle is now fully restored and in the collection of the National Museum of Australia . In 1924, Citroën began

670-477: A 38.2% share of Citroën and on 9 April 1976 they increased their stake of the then bankrupt company to 89.95%, thus creating the PSA Group (where PSA is short for Peugeot Société Anonyme ), becoming PSA Peugeot Citroën . In May 1975 Maserati was sold to De Tomaso and the new Italian owner was thereby able to exploit the sales potential of the models and technology developed by Citroën, as well as to utilise

804-467: A French aeronautical engineer, became the first person to reasonably predict the power needed for sustained flight. Otto Lilienthal , the first person to become highly successful with glider flights, was also the first to propose thin, curved airfoils that would produce high lift and low drag. Building on these developments as well as research carried out in their own wind tunnel, the Wright brothers flew

938-733: A business relationship with the American engineer Edward G. Budd . From 1899, Budd had worked to develop stainless steel bodies for railroad cars, for Pullman in particular. Budd went on to manufacture steel bodies for many automakers, Dodge being his first big auto client. At the Paris Motor Show in October 1924, Citroën introduced the Citroën B10 , the first all-steel body in Europe. These automobiles were initially successful in

1072-410: A carpenter working on a set of gears with a fish bone structure. These gears were less noisy, and more efficient. Citroën bought the patent for very little money, leading to the invention that is credited to Citroën: double helical gears. In 1901, at the age of 23, André Citroën partnered with André Boas and Jacques Hinstin, whom he had known since their days at Lycée Condorcet . Together, they invested

1206-450: A company, which was being picketed by striking workers who had been blocking access to the factories for four weeks. The demonstration was successful and six days later work at the plants resumed. Jacques Lombard, one of the company's senior managers, had gone public with his concerns, criticising the strikes. PSA gradually diluted Citroën's ambitious, highly individualistic, and distinctive approach to engineering and styling. All through

1340-511: A considerable reputation within the French automotive sector as the creator, in 1909, of a little car called Le Zèbre . André Citroën's mandate was characteristically demanding and characteristically simple: to produce an all-new design for a 10 HP car that would be better equipped, more robust and less costly to produce than any rival product at the time. The result was the Type A , announced to

1474-482: A continuum. Continuum flow fields are characterized by properties such as flow velocity , pressure , density , and temperature , which may be functions of position and time. These properties may be directly or indirectly measured in aerodynamics experiments or calculated starting with the equations for conservation of mass, momentum , and energy in air flows. Density, flow velocity, and an additional property, viscosity , are used to classify flow fields. Flow velocity

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1608-745: A costly, complex and expensive to maintain, air suspension , that avoided the Citroën-patented technology. By 1975, the Mercedes-Benz 450SEL 6.9 was finally produced with this proven system and Mercedes-Benz continues to offer variations on this technology today. During Citroën's 1968–1975 venture with Maserati , the Citroën high-pressure hydraulic system was used on several Maserati models : for power clutch operation (Bora); power pedal adjustment (Bora); pop-up headlights (Bora, Merak); brakes (Bora, Merak, Khamsin); steering (Khamsin) and

1742-487: A design perspective, CEO Pierre Bercot considered a hatchback layout too utilitarian . The GS's initial fastback design, with a separate trunk/boot, was controversial, though the 1974 CX shared a similar configuration. The trunk/boot was nevertheless large, in part due to the positioning of the spare wheel within the engine compartment. From September 1971, the GS was also available as a four door station wagon (estate) and

1876-574: A drag coefficient of 0.318, fully independent hydro-pneumatic brakes and self-levelling suspension , and air-cooled flat-four engine, the GS was styled by Robert Opron , with a low nose, a two-box silhouette, semi-enclosed rear wheels and a sharply vertical Kamm-tail . When the GS was named the European Car of the Year for 1971, the design was noted as technologically advanced, with class leading comfort, safety and aerodynamics. The GS filled

2010-447: A fleet of the larger CX model (as well as several Volvos ). Citro%C3%ABn Citroën ( French pronunciation: [sitʁɔɛn] ) is a French automobile brand . The "Automobiles Citroën" manufacturing company was founded on 4 June 1919 by André Citroën . Citroën has been owned by Stellantis since 2021 and previously was part of the PSA Group after Peugeot acquired 89.95% share in 1976. Citroën's head office

2144-410: A flow field) enables the calculation of forces and moments acting on the object. In many aerodynamics problems, the forces of interest are the fundamental forces of flight: lift , drag , thrust , and weight . Of these, lift and drag are aerodynamic forces, i.e. forces due to air flow over a solid body. Calculation of these quantities is often founded upon the assumption that the flow field behaves as

2278-438: 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

2412-492: A four speed gearbox , these were able to pull this car up to steady 151 km/h (94 mph) at 6,250 rpm (with a 1,222 cc engine), due to the very aerodynamic body shape. Citroën's 3-speed C-Matic semi- automatic transmission was available as an alternative to the manual gearbox. With the introduction of the GSA a 5-speed gearbox was offered, which made cruising at high speeds more comfortable and economical (the top speed

2546-448: A large gap in the middle range of the market. In 1956, Citroën developed the C10, a bubble car prototype to fill the gap in its range between the large DS and the tiny 2CV . Development continued with ideas like a Wankel engine and hydropneumatic suspension suggested as possibilities, with a new, modern body to match. Another iteration was the "C60," which resembled an Ami 6 with

2680-685: A licence to produce them. This resulted in the United States Army Ordnance Department building a prototype in 1939. In December 1942, it went into production with the M2 Half Track Car and M3 Half-track versions. The U.S. eventually produced more than 41,000 vehicles in over 70 versions between 1940 and 1944. After their 1940 occupation of France, the Nazis captured many of the Citroën half-track vehicles and armored them for their own use. Citroën used

2814-497: A long, smooth nose. In 1963, development had moved to "Project F", which was close to being production-ready. Citroën decided the car was too similar to the 1965 Renault 16 and by 1967 Project F was suspended. Many of the mechanical components continued to "Project G", which became the GS. The GS was designed by Robert Opron , with a smooth two box design that bears some resemblance to the 1967 design study by Pininfarina Berlina Aerodinamica. On 24 August 1970, Citroën launched

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2948-692: A mix thereof were built in Cakung in East Jakarta, Indonesia by PT Alun Indah. Indonesian production continued until at least 1990. Renowned moped manufacturer Tomos in Yugoslavia (now Slovenia) also assembled the GS saloon at their plant in Koper . In 1973 a new company, Cimos, was formed by Citroën, Iskra , and Tomos and they took over production. Like the Indonesian models, Cimos sometimes used

3082-708: A model in the profitable middle range of the European market, plus the massive development costs a string of new models: the GS , GS Birotor , CX , SM , Maserati Bora , Maserati Merak , Maserati Quattroporte II , and Maserati Khamsin . Each of these models is a technological marvel in its own right. Thus, forty years after the bankruptcy related to the Traction Avant , Citroën went bankrupt again, losing its existence as an independent entity; selling Berliet and Maserati and closing Comotor. Fearing large job losses due to

3216-600: A museum of its many significant vehicles: the Conservatoire with 300 cars. In line with the severe decline in European car sales after 2009, worldwide sales of vehicles declined from 1,460,373 in 2010 to 1,435,688 in 2011, with 961,156 of these sold in Europe. In 2011, the PSA Group was close to forming a partnership with BMW, for the development of electric and hybrid vehicles, but the talks fell through, shortly after Groupe PSA, Citroën's parent company, had announced

3350-755: A new one between PSA and Toyota is now producing cars like the Citroën C1 in the Czech Republic . The China joint venture began selling cars in 1984 and building them in 1994. The range of family cars there included the C3 and Xsara and locally designed cars like the Fukang and Elysée models. By 2014 the brand had increased its Chinese sales by 30%, amid overall market growth of 11%, and ranked highest in China's 2014 JD Power satisfaction survey. Citroën

3484-461: A partnership with GM, which later also failed. Dongfeng Peugeot-Citroën continues growing, and has developed eight new car designs exclusively for the China market. By 2016 Citroën (and Peugeot ) faced the same challenge as Volkswagen in China: there were too many sedans and hatchbacks , but not enough models in the strong selling SUV and minivan /MPV categories. The brand ranked highest in

3618-511: A proposed sale of the Citroën company. The deal nearly closed, but General Motors ultimately decided that its management and capital would be too overstretched by the takeover, thus, Citroën remained independent until 1935. Between 1921 and 1937, Citroën produced half-track vehicles for off-road and military uses, using the Kégresse track system. In the 1920s, the U.S. Army purchased several Citroën-Kégresse vehicles for evaluation followed by

3752-410: A range of flow 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, while some of

3886-525: A separate chassis, and instead using the body of the car itself as its main load-bearing structure. In 1954, they produced the world's first hydropneumatic self-levelling suspension system; then the revolutionary DS , the first mass-produced car with modern disc brakes , in 1955; and in 1967 they introduced in several of their models swiveling headlights that allowed for greater visibility on winding roads. These cars have received various national and international awards, including three European Car of

4020-403: A series of financial and development decisions, aiming to build on its strength of the 1950s with the successful 2CV, Type H, and DS models. Nevertheless, these maneuvers were insufficiently effective, and Citroën went bankrupt again in 1974. These measures were to address two key gaps facing the company: These steps include: The teams of Charles Marchetti and Citroën began working together on

4154-537: A significant portion of Citroën's inheritance to found the company "Citroën, Hinstin et Cie," a manufacturing business specializing in gears, particularly V-shaped helical gears. The company started with about ten workers in the Faubourg Saint-Denis area of the 10th arrondissement of Paris and moved in 1912 to 31 Quai de Grenelle in the 15th arrondissement of Paris . André Citroën (1878–1935) built armaments for France during World War I ; after

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4288-456: A similar two-door "service" van. Both the early GS (until 1976) and the GSA were fitted with a rotating drum speedometer (similar in construction to bathroom scales), rather than the dials found in a conventional instrument panel. The later GS (from 1977 until the introduction of the GSA) had a conventional speedometer The GS's radio was placed between the seats, and the parking brake was located on

4422-493: A single Solex carburetor and have a bespoke five-speed gearbox with shaft drive. About 650 of these were built between 1981 and 1988, most of them for French police authorities. A two rotor GS was launched in 1973. Dubbed the Citroën GS Birotor (also called Citroën GZ), it featured a much more powerful 79 kW (106 hp) Wankel birotor produced by the joint NSU-Citroën Comotor project. This style of motor

4556-541: A small car (2CV), a delivery van (Type H) and a large, swift family car (DS). These were widely regarded by contemporary journalists as avant garde , even radical, solutions to automotive design. Thus began a decades-long period of unusual brand loyalty , normally seen in the automobile industry only in niche brands, like Porsche and Ferrari . Citroën unveiled the Citroën 2CV or Deux Chevaux signifying two tax horsepower and initially only 9 hp (6.7 kW), at

4690-663: A study to clarify and support brand differentiation within a brand portfolio". Citroën entered the Indian market in early 2021 with the launch of the C5 Aircross SUV manufactured at the Hindustan Motors Thiruvallur plant in Tamil Nadu , India. In early 2009, Citroën announced the development of the premium brand DS , for Different Spirit or Distinctive Series (although the reference to

4824-435: A technically sophisticated 18HP automobile he could produce in his factory once peace returned. Long before that happened, however, he had modified his vision and decided, like Henry Ford , that the best post-war opportunities in auto-making would involve a lighter car of good quality, but made in sufficient quantities to be priced enticingly. In February 1917 Citroën contacted another engineer, Jules Salomon , who already had

4958-521: A three-speed semi-automatic transmission were combined with a more luxurious interior and flared fenders to set the Birotor apart from its lesser siblings. The Birotor cost as much as the larger Citroën DS , and 70 percent more than the standard GS. The fuel economy was worse than the largest DS – the DS23EFI. Since it was not economical for its size, and was launched in October 1973, the exact start of

5092-418: Is a flow in which density is constant in both time and space. Although all real fluids are compressible, a flow is often approximated as incompressible if the effect of the density changes cause only small changes to the calculated results. This is more likely to be true when the flow speeds are significantly lower than the speed of sound. Effects of compressibility are more significant at speeds close to or above

5226-526: Is a global brand, except in North America, where the company has not returned since the SM was effectively banned in 1974 for not meeting U.S. National Highway Traffic Safety Administration (NHTSA) bumper height regulations. In 2016, Peugeot–Citroën South Africa (PCSA) announced that they were going to stop importing new Citroën models into South Africa in order to focus on increasing Peugeot's sales in

5360-448: Is a solution in one dimension to both the momentum and energy conservation equations. The ideal gas law or another such equation of state is often used in conjunction with these equations to form a determined system that allows the solution for the unknown variables. Aerodynamic problems are classified by the flow environment or properties of the flow, including flow speed , compressibility , and viscosity . External aerodynamics

5494-416: 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. The incompressible and compressible flow regimes produce many associated phenomena, such as boundary layers and turbulence. The concept of a boundary layer is important in many problems in aerodynamics. The viscosity and fluid friction in

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5628-503: Is associated with the frictional forces in a flow. In some flow fields, viscous effects are very small, and approximate solutions may safely neglect viscous effects. These approximations are called inviscid flows. Flows for which viscosity is not neglected are called viscous flows. Finally, aerodynamic problems may also be classified by the flow environment. External aerodynamics is the study of flow around solid objects of various shapes (e.g. around an airplane wing), while internal aerodynamics

5762-407: Is called laminar flow . Aerodynamics is a significant element of vehicle design , including road cars and trucks where the main goal is to reduce the vehicle drag coefficient , and racing cars , where in addition to reducing drag the goal is also to increase the overall level of downforce . Aerodynamics is also important in the prediction of forces and moments acting on sailing vessels . It

5896-409: Is called potential flow and allows the differential equations that describe the flow to be a simplified version of the equations of fluid dynamics , thus making available to the aerodynamicist a range of quick and easy solutions. 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

6030-403: Is designed to absorb bumps and ripples that would be uncomfortable in a conventionally sprung car with just a slight body movement. The vehicle had a front-wheel drive layout and was powered by an air-cooled flat-four engine . A series of small engines were available, displacing 1,015, 1,129, 1,222 and 1,299 cc. Power ranged from 40 kW (54 hp) to 49 kW (66 hp). Mated to

6164-777: Is located in the Stellantis Poissy Plant in Saint-Ouen-sur-Seine since 2021 (previously in Rueil-Malmaison) and its offices studies and research in Vélizy-Villacoublay, Poissy (CEMR), Carrières-sous-Poissy and Sochaux-Montbéliard. In 1934, the firm established its reputation for innovative technology with the Traction Avant . This was the world's first car to be mass-produced with front-wheel drive and four-wheel independent suspension, as well as unibody construction, omitting

6298-534: Is mounted on the dashboard as opposed to being mounted between the front seats. In-car entertainment can be fitted in the space that would have been utilised by the handbrake. As with other Citroën cars, the hydraulic system depressurizes over several hours, so the car will gradually sink to the bump stops when the engine is off. The GS' 1.3-litre engine was also used in the French BFG 1301  [ fr ] "Odyssée" motorcycle. The engines were equipped with

6432-549: Is noted for its smooth power delivery which complemented the luxurious ride quality of the hydropneumatic suspension. Even better, the engine was small relative to its power, an advantage for Tax horsepower calculations, which drive automobile design in France. The Birotor was extensively re engineered for the Comotor 624 engine. Discs all around (ventilated in front), different wheels with a five-bolt pattern rather than three, and

6566-438: Is the principal user benefit: the car maintains a constant ride height above the road, regardless of passenger and cargo load and despite the very soft suspension. Hydropneumatic suspension is uniquely able to absorb road irregularities without disturbing the occupants and is often compared to riding on a magic carpet for this reason. These vehicles shared the distinguishing feature of rising to operating ride height when

6700-497: 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

6834-415: Is the study of flow through passages inside solid objects (e.g. through a jet engine). Unlike liquids and solids, gases are composed of discrete molecules which occupy only a small fraction of the volume filled by the gas. On a molecular level, flow fields are made up of the collisions of many individual of gas molecules between themselves and with solid surfaces. However, in most aerodynamics applications,

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6968-426: Is used because gas flows with a Mach number below that value demonstrate changes in density of less than 5%. Furthermore, that maximum 5% density change occurs at the stagnation point (the point on the object where flow speed is zero), while the density changes around the rest of the object will be significantly lower. Transonic, supersonic, and hypersonic flows are all compressible flows. The term Transonic refers to

7102-418: Is used in the design of mechanical components such as hard drive heads. Structural engineers resort to aerodynamics, and particularly aeroelasticity , when calculating wind loads in the design of large buildings, bridges , and wind turbines . The aerodynamics of internal passages is important in heating/ventilation , gas piping , and in automotive engines where detailed flow patterns strongly affect

7236-468: Is used to classify flows according to speed regime. Subsonic flows are flow fields in which the air speed field is always below the local speed of sound. Transonic flows include both regions of subsonic flow and regions in which the local flow speed is greater than the local speed of sound. Supersonic flows are defined to be flows in which the flow speed is greater than the speed of sound everywhere. A fourth classification, hypersonic flow, refers to flows where

7370-671: Is why today cars are more like the Traction Avant than the Model T under the skin. In 1934 Citroën commissioned the American Budd Company to create a prototype, which evolved into the 7 fiscal horsepower ( CV ), 32 hp (24 kW) Traction Avant. Achieving quick development of the Traction Avant, tearing down and rebuilding the factory (in five months) and the extensive marketing efforts, were investments that resulted too costly for Citroën to do all at once, causing

7504-409: The 1973 oil crisis , the Birotor version achieved poor sales and was quickly pulled from the market, after 847 units were sold. In 1975, Peugeot S.A, which had been a competitor until then, took over Citroën S.A. as its subsidiary. PSA attempted to buy back and scrap each Birotor, as it did not want to support the model with spare parts. A few of these remarkable vehicles have nonetheless survived in

7638-647: The Dyane , and soon the Peugeot 104 based Citroën Visa and Citroën LNA . Peugeot was typically prudent with its own finances. Then, PSA purchased the ageing assets and substantial liabilities of Chrysler Europe for $ 1, leading to losses from 1980 to 1985. PSA resurrected the Talbot name for the Chrysler cars, but stopped producing cars with the badge in 1987 as the cars were considered unreliable and poorly-made. At

7772-631: The Eiffel Tower as the world's largest advertising sign, as recorded in Guinness World Records . He also sponsored expeditions in Asia ( Croisière Jaune ), North America (Croisière Blanche) and Africa (Croisière Noire), demonstrating the potential for motor vehicles equipped with the Kégresse track system to cross inhospitable regions. These expeditions conveyed scientists and journalists . Demonstrating extraordinary toughness,

7906-468: The Ford Model T – a body bolted onto a ladder frame which held all the mechanical elements of the car, a solid rear axle that rigidly connected the rear wheels and rear wheel drive . The Model T school of automobile engineering proved popular because it was considered cheap to build, although it did pose dynamic defects as automobiles were becoming more capable, and resulted in heavier cars, which

8040-773: The German occupation of France in World War II Boulanger refused to meet Dr. Ferdinand Porsche or communicate with the German authorities except through intermediaries. He organized a "go slow" on production of trucks for the Wehrmacht , many of which were sabotaged at the factory by putting the notch on the oil dipstick in the wrong place, which resulted in engine seizure. In 1944 when the Gestapo headquarters in Paris

8174-524: The Paris Salon in 1948. The car became a bestseller, achieving the designer's aim of providing rural French people with a motorized alternative to the horse . It was unusually inexpensive to purchase and, with its small two cylinder engine, inexpensive to run as well. The 2CV pioneered a very soft, interconnected suspension, but did not have the more complex self-levelling feature . This car remained in production, with only minor changes, until 1990 and

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8308-416: 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

8442-438: The 1980s, Citroën models became increasingly Peugeot-like. The 1982 BX used the hydropneumatic suspension system and had a typical Citroënesque appearance, whilst being powered by Peugeot-derived engines and using the floorpan later seen on the Peugeot 405 . In this respect PSA followed the worldwide motor industry trend of platform sharing which is a logical way to reduce costs whilst selling apparently different models. By

8576-465: The 2014 customer satisfaction survey by JD Power in China, above luxury brands like Mercedes-Benz and BMW , and above mass market brands, like Volkswagen, ranking only thirteenth and seventeenth respectively. In the first ten months of 2014 in China, the sales of Dongfeng Citroën cars increased by 30% in an overall market growth of 11%. Despite the near-death financial experience of PSA Peugeot Citroën in 2014, and financial rescue by Dongfeng Motors ,

8710-601: The 2019 Geneva International Motor Show , the manufacturer presented the Ami One concept car to celebrate its 100th anniversary. Then, in May 2019, it unveiled the Citroën 19_19 Concept at the Viva Technology show in Paris. In the early 1980s, Citroën was targeted by union action. On 25 May 1982, events led to a mass demonstration in the streets of Paris, when approximately 27,000 workers affirmed their wish to work at

8844-476: The 526,443 of 1971, and enough to lift the company past Peugeot into second place among French auto makers when ranked by sales volume. The older models continued to sell well: the peak production period of the DS was 1970, and 2CV was in 1974. As the 1970s progressed, circumstances became more unfavourable. In 1973, Fiat sold back to Michelin its 49% stake in the PARDEVI holding company that owned Citroën,

8978-439: The Citroën and DS brands worked to develop new technologies with the hope to grow 15% by 2020, according to Citroën CEO Linda Jackson and DS CEO Yves Bonnefont . In the end sales of the Citroën and DS brands in Europe and China fell by 22% by 2019, and fell even further during the 2020 COVID outbreak. In January 2020, Linda Jackson was succeeded as CEO of Citroën by the deputy CEO Vincent Cobée , and she would instead "lead

9112-431: The Citroën and Fiat joint announcement indicated that the benefits foreseen for their union in 1968 had failed to materialise. This was not in line with the tyre company's long-term strategy of ending involvements in the car manufacturing business and created a very unstable ownership situation. The company suffered another financial blow with the 1973 energy crisis . The gamble on Comotor and Maserati showed that there

9246-541: The GS. The body style was as a Berline (a four-door saloon with three side windows), in a fastback style with a sharp Kammback . The aerodynamics gave the best drag coefficient of any vehicle at the time. On its launch, its main competitors in Europe included the Fiat 128 , Ford Escort , Renault 6 and Vauxhall Viva . The GS's aerodynamics enabled the car to make the best of the available power, but when introduced,

9380-559: The March 1971 issue of CAR magazine, automotive journalist L.J.K. Setright noted that with the arrival of the GS, the automotive industry would have to re-evaluate its offerings, seeing what he described as a "lemming-like rush towards a sea of mediocrity…" The GS took 14 years to develop from initial design to launch. The 1955 DS19 was 65% more expensive than the car it replaced, the Citroën Traction Avant , leaving

9514-488: The Rosalie, the first commercially available passenger car with a diesel engine , developed with Harry Ricardo . The Traction Avant is a car that pioneered the mass production of three revolutionary features that are still in use today: a unitary body with no separate frame , four wheel independent suspension and front-wheel drive . Whereas for many decades, the vast majority of motor cars were similar in conception to

9648-483: The Société de Vente des Automobiles Citroën (SOVAC). It went even further by entering in its capital and being represented on the board; the three directors sent by Lazard were Raymond Philippe, Andre Meyer and Paul Frantzen. André Citroën perceived the need to differentiate his product, to avoid the low price competition surrounding his conventional rear drive models in the late 1920s and early 1930s. In 1933 he introduced

9782-641: The USA. A US export model was nearly finished when Citroën withdrew from the US market, with a few dozen cars brought over in 1971 for testing purposes and to be displayed in showrooms. After the project was cancelled, these orphaned cars were sold, mostly to employees of the dealerships. A sealed-beam headlight design was developed, and although never used as intended it was installed in Yugoslav- and Indonesian-assembled models as it made light replacement cheaper and easier. In

9916-415: The Year awards. Born to a Dutch father and a Polish mother, both of Jewish heritage, André Citroën was born in Paris on February 5, 1878. At the age of 7 his father committed suicide as a result of a failed business venture. Citroën was a graduate of the École Polytechnique in 1900. In that year he visited Poland, the homeland of his mother, who had recently passed away. During that holiday, he saw

10050-412: The air is approximated as being significant only in this thin layer. This assumption makes the description of such aerodynamics much more tractable mathematically. In aerodynamics, turbulence is characterized by chaotic property changes in the flow. These include low momentum diffusion, high momentum convection, and rapid variation of pressure and flow velocity in space and time. Flow that is not turbulent

10184-568: The airflow is not supersonic. 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

10318-580: The amount of change of density in the flow. When the effects of compressibility on the solution are small, the assumption that density is constant may be made. The problem is then an incompressible low-speed aerodynamics problem. When the density is allowed to vary, the flow is called compressible. In air, compressibility effects are usually ignored when the Mach number in the flow does not exceed 0.3 (about 335 feet (102 m) per second or 228 miles (366 km) per hour at 60 °F (16 °C)). Above Mach 0.3,

10452-561: The body panels; it was named 2010 Car of the Year by Top Gear Magazine , and was awarded best supermini four times in a row by the JD Power Satisfaction Survey UK and second most efficient supermini (Citroën DS3 1.6 e-HDi 115 Airdream : True MPG 63.0mpg) by What car ? behind the C3 . In 2013 the DS3 was again the best-selling premium subcompact car, with 40% of the European market share, validating

10586-423: The brake pedal response. The powered system was different from the typical assisted systems in that there was virtually no travel on the brake pedal even when braking hard. The hydraulic suspension allowed the car to be raised for rough terrain at low speeds (a feature taking account of the country lanes of its native France) and to full height for easy access to the partially enclosed rear wheels. The hand brake lever

10720-517: The business model of this product development. Aerodynamics Modern aerodynamics only dates back to the seventeenth century, but aerodynamic forces have been harnessed by humans for thousands of years in sailboats and windmills, and images and stories of flight appear throughout recorded history, such as the Ancient Greek legend of Icarus and Daedalus . Fundamental concepts of continuum , drag , and pressure gradients appear in

10854-486: The car was considered underpowered. In September 1972 Citroën addressed the issue with the introduction of an optional 1,222 cc engine. Claimed power increased from 41 kW (55 bhp; 56 PS) to 45 kW (60 bhp; 61 PS), with improved torque. Both the second gear and final drive ratios were adjusted, increasing the vehicle speed per 1,000 rpm from 23 km/h (14.3 mph) to 24.5 km/h (15.2 mph). Larger front brake discs were also fitted. From

10988-690: The choice between statistical mechanics and the continuous formulation of aerodynamics. The assumption of a fluid continuum allows problems in aerodynamics to be solved using fluid dynamics conservation laws . Three conservation principles are used: Together, these equations are known as the Navier–Stokes equations , although some authors define the term to only include the momentum equation(s). The Navier–Stokes equations have no known analytical solution and are solved in modern aerodynamics using computational techniques . Because computational methods using high speed computers were not historically available and

11122-462: The continuum assumption is reasonable. The continuum assumption is less valid for extremely low-density flows, such as those encountered by vehicles at very high altitudes (e.g. 300,000 ft/90 km) or satellites in Low Earth orbit . In those cases, statistical mechanics is a more accurate method of solving the problem than is continuum aerodynamics. The Knudsen number can be used to guide

11256-601: The country. In May 2019, it was reported that PCSA would re-introduce the Citroën brand into South Africa, this was later confirmed by PCSA, in August 2019, that new Citroën models will go on sale in the middle of October 2019. From 2003 to 2010, Citroën produced the C3 Pluriel, an unusual convertible with allusions to the 1948–1990 2CV model, both in body style (such as the bonnet) and in its all-round practicality. In 2001 it celebrated its history of innovation when it opened

11390-526: The dashboard. Adjacent to the radio was a suspension height adjustment lever. The steering wheel was single-spoke design, minimizing its potential intrusion on the driver in the event of an impact. On the later GSA, controls were organized in flanking satellites and a diagram of the car provided information on indicator lights or mechanical problems. The GS was offered in four trims: G Special (base), GS Club (midrange), GS X (sports), and GS Pallas (luxury). The GS X and Pallas were only offered as saloons. The GS

11524-463: The desire to improve the aerodynamic efficiency of current aircraft and propulsion systems, continues to motivate new research in aerodynamics, while work continues to be done on important problems in basic aerodynamic theory related to flow turbulence and the existence and uniqueness of analytical solutions to the Navier–Stokes equations. Understanding the motion of air around an object (often called

11658-501: The development costs and new factory for the DS-replacing Citroën CX , the 1973/1974 oil crisis , and an aborted Wankel rotary engine , led Citroën to declare bankruptcy in 1974. The GS met with instant market acceptance and was the largest selling Citroën model for many years. 1,896,742 GS models and 576,757 GSA models were produced in total. Unlike the 2CV, Ami, DS and SM, the GS was never officially imported to

11792-453: The development of the RE-2  [ fr ] helicopter . From a model range perspective, the 1970s started well, supported by the successful launch of the long-awaited mid-size Citroën GS , finally filling the huge gap between the 2CV and the DS – with a 1-litre, hydropneumatically suspended car. The GS went on to sell 2.5 million units; 601,918 cars were produced in 1972 alone, up from

11926-437: The discrete molecular nature of gases is ignored, and the flow field is assumed to behave as a continuum . This assumption allows fluid properties such as density and flow velocity to be defined everywhere within the flow. The validity of the continuum assumption is dependent on the density of the gas and the application in question. For the continuum assumption to be valid, the mean free path length must be much smaller than

12060-506: The early DS models experienced teething issues with the complex hydraulic system, eventually, the hydraulic seals and system component design were sorted, becoming reliable. Licensing such a technological leap forward was pursued to a limited extent: in 1965 the Rolls-Royce Silver Shadow used this type of suspension, while the 1963 Mercedes-Benz 600 and Mercedes-Benz 300SEL 6.3 tried to replicate its advantages with

12194-509: The engine was turned on, like a "mechanical camel" (per Car & Driver magazine). A lever ( later replaced by an electronic switch ) beside the driver's seat allowed the driver to adjust the height of the car; this height adjustability allows for the clearing of obstacles, fording shallow (slow-moving) streams and changing tyres. Since Citroën was underfunded, its vehicles had the tendency to be underdeveloped at launch, with limited distribution and service networks outside France. Consequently,

12328-430: The entire Quattroporte II prototype, which was a four-door Citroën SM under the skin. Citroën was one of the early pioneers of the now-widespread trend of aerodynamic automobile design, which helps to reduce fuel consumption and to improve high-speed performance, by reducing wind resistance . The DS could happily cruise at 160 km/h (100 mph) without any discomfort for the occupants. The firm began using

12462-481: The financial ruin of the company. In December 1934, despite the assistance of the Michelin company, Citroën filed for bankruptcy. Within the month, Michelin , already the car manufacturer's largest creditor, became its principal shareholder. However, the technologically advanced Traction Avant had met with market acceptance, and the basic philosophy of cutting-edge technology used as a differentiator, continued until

12596-504: The first person to identify the four aerodynamic forces of flight ( weight , lift , drag , and thrust ), as well as the relationships between them, and in doing so outlined the path toward achieving heavier-than-air flight for the next century. In 1871, Francis Herbert Wenham constructed the first wind tunnel , allowing precise measurements of aerodynamic forces. Drag theories were developed by Jean le Rond d'Alembert , Gustav Kirchhoff , and Lord Rayleigh . In 1889, Charles Renard ,

12730-673: The first powered airplane on December 17, 1903. During the time of the first flights, Frederick W. Lanchester , Martin 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 behind thin-airfoil and lifting-line theories as well as work with boundary layers . As aircraft speed increased designers began to encounter challenges associated with air compressibility at speeds near

12864-477: The flow pattern ahead of the object and giving the impression that the fluid "knows" the object is there by seemingly adjusting its movement and is flowing around it. In a supersonic flow, however, the pressure disturbance cannot propagate upstream. Thus, when the fluid finally reaches the object it strikes it and the fluid is forced to change its properties – temperature , density , pressure , and Mach number —in an extremely violent and irreversible fashion called

12998-458: The flow speed is much greater than the speed of sound. Aerodynamicists disagree on the precise definition of hypersonic flow. Compressible flow accounts for varying density within the flow. Subsonic flows are often idealized as incompressible, i.e. the density is assumed to be constant. Transonic and supersonic flows are compressible, and calculations that neglect the changes of density in these flow fields will yield inaccurate results. Viscosity

13132-570: The flow speed is much greater than the speed of sound. Aerodynamicists disagree over the precise definition of hypersonic flow; a rough definition considers flows with Mach numbers above 5 to be hypersonic. The influence of viscosity on the flow dictates a third classification. Some problems may encounter only very small viscous effects, 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. An incompressible flow

13266-418: The gap in Citroën's range, between the 2CV and Ami economy cars and the luxurious DS executive sedan . The DS had moved significantly upmarket from its predecessor the Citroën Traction Avant , and beyond the finances of most French motorists. Leaving this market gap open for fifteen years allowed other manufacturers entry into the most profitable, high volume market segment in France. This combined with

13400-492: The hands from the single-spoked steering wheel; similar to the CX layout. The GSA was joined and gradually replaced by the larger BX in 1982, with production continuing in reduced volumes until 1986. Citroën did not return to the small family hatchback market until the launch of the ZX in 1991. Contemporary journalists noted the smooth ride quality – the hydropneumatic suspension

13534-611: The hands of collectors, many without titles for some time as PSA did not want to recognize the cars. The GS and GSA were built in a number of countries besides France. 385,000 units were built in Vigo, Spain Besides Portugal, production or assembly took place in countries as varied as South Africa, Chile and Rhodesia (now Zimbabwe). The South African model was also available as the "GS-X2 Le Mans" special edition, only available in silver, red or black with an all-white interior with

13668-465: The high computational cost of solving these complex equations now that they are available, simplifications of the Navier–Stokes equations have been and continue to be employed. The Euler equations are a set of similar conservation equations which neglect viscosity and may be used in cases where the effect of viscosity is expected to be small. Further simplifications lead to Laplace's equation and potential flow theory. Additionally, Bernoulli's equation

13802-575: The historical Citroën DS is evident), to run in parallel to its mainstream cars. The slogan of the DS car marque is "Spirit of avant-garde". This new series of cars started early in 2010, with the DS3 , a small car based on the floorpan of the new C3. The DS3 is based on the concept that preceded the C3 Pluriel production model and the Citroën DS Inside concept car. The DS3 is customisable with various roof colours contrasting with

13936-466: The image of the Maserati brand in a downward brand extension to sell 40,000 of the newly designed Bi-Turbo models. The truck manufacturing company Berliet was sold to Renault . This new PSA venture was a financial success from 1976 to 1979. Citroën had two successful new designs in the market, the GS and CX . In the wake of the oil crisis, the brand also had resurgent sales for the 2CV and

14070-452: The late 1980s, many of the distinctive features of the brand had been removed or altered. Peugeot's conventional switchgear replaced Citroën's quirky but ergonomic Lunule designs, complete with self-cancelling indicators that Citroën had refused to adopt on ergonomic grounds. The cars were "more banal and conventional", but also able to break into new markets, like fleet vehicles in the UK. In

14204-493: The late 1990s. Pierre Michelin became the chairman of Citroën early in 1935. Pierre-Jules Boulanger , his deputy, became the vice-president and chief of the engineering and design departments. In 1935, the founder André Citroën died from stomach cancer. Pierre-Jules Boulanger had been a First World War air reconnaissance photography specialist with the French Air Force ; he was capable and efficient and finished

14338-433: The length scale of the application in question. For example, many aerodynamics applications deal with aircraft flying in atmospheric conditions, where the mean free path length is on the order of micrometers and where the body is orders of magnitude larger. In these cases, the length scale of the aircraft ranges from a few meters to a few tens of meters, which is much larger than the mean free path length. For such applications,

14472-484: The marketplace, but soon competitors who were still using a wooden structure for their vehicles, introduced new body designs. Citroën, who did not redesign the bodies of his cars, still sold in large quantities nonetheless, the cars' low price being the main selling point, which factor however caused Citroën to experience heavy losses. In 1927, the bank Lazard helped Citroën by bringing new much-needed funds, as well as by renegotiating its debt—for example, by buying out

14606-684: The meantime Citroën expanded into many new global markets. Beyond existing manufacturing plants in Argentina , Chile , Vietnam , and Yugoslavia , it added Iran , Greece , Romania , and China . In the late 1970s, the firm developed a small car for production in Romania known as the Oltcit , which it sold in Western Europe as the Citroën Axel . That joint venture has now ended, but

14740-456: The more general Euler equations which could be applied to both compressible and incompressible flows. The Euler equations were extended to incorporate the effects of viscosity in the first half of the 1800s, resulting in the Navier–Stokes equations . The Navier–Stokes equations are the most general governing equations of fluid flow but are difficult to solve for the flow around all but the simplest of shapes. In 1799, Sir George Cayley became

14874-579: The performance of the engine. Urban aerodynamics are studied by town planners and designers seeking to improve amenity in outdoor spaces, or in creating urban microclimates to reduce the effects of urban pollution. The field of environmental aerodynamics describes ways in which atmospheric circulation and flight mechanics affect ecosystems. Aerodynamic equations are used in numerical weather prediction . Sports in which aerodynamics are of crucial importance include soccer , table tennis , cricket , baseball , and golf , in which most players can control

15008-485: The point where entire aircraft can be designed using computer software, with wind-tunnel tests followed by flight tests to confirm the computer predictions. Understanding of supersonic and hypersonic aerodynamics has matured since the 1960s, and the goals of aerodynamicists have shifted from the behaviour of fluid flow to the engineering of a vehicle such that it interacts predictably with the fluid flow. Designing aircraft for supersonic and hypersonic conditions, as well as

15142-451: The poor cash flow situation and the unstable ownership structure, the French government arranged talks between Citroën and Michelin culminating in the merger of Automobiles Citroën and Automobiles Peugeot into a single company. Thus, one year after the break with Fiat, on 24 June 1974 Citroën announced the new partnership, this time with Peugeot. to whom Michelin agreed to transfer control of the business. In December 1974 Peugeot S.A. acquired

15276-622: The press in March 1919, just four months after the guns fell silent. The first production Type A emerged from the factory, located at Quai de Javel , Vaugirard , Paris , at the end of May 1919 and in June it was exhibited at a show room at Number 42, on the Champs-Élysées in Paris which normally sold Alda cars . Citroën persuaded the owner of the Alda business, Fernand Charron , to lend him

15410-421: The problem flow should be described using compressible aerodynamics. According to the theory of aerodynamics, a flow is considered to be compressible if the density changes along a streamline . This means that – unlike incompressible flow – changes in density are considered. In general, this is the case where the Mach number in part or all of the flow exceeds 0.3. The Mach 0.3 value is rather arbitrary, but it

15544-501: The show-room, which is still in use today. This C42 showroom is where the company organises exhibitions and shows its vehicles and concept cars. A few years later, Charron would be persuaded to become a major investor in the Citroën business. On 7 July 1919, the first customer took delivery of a new Citroën 10HP Type A . In the same year, it produced 30 cars daily, totaling 2,810 vehicles, with 12,244 produced in 1920. That same year, André Citroën briefly negotiated with General Motors

15678-450: The speed of sound. The Mach number is used to evaluate whether the incompressibility can be assumed, otherwise the effects of compressibility must be included. Subsonic (or low-speed) aerodynamics describes fluid motion in flows which are much lower than the speed of sound everywhere in the flow. There are several branches of subsonic flow but one special case arises when the flow is inviscid , incompressible and irrotational . This case

15812-459: The speed of sound. The differences in airflow under such conditions lead to problems in aircraft control, increased drag due to shock waves , and the threat of structural failure due to aeroelastic flutter . 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 the supersonic flow. Macquorn Rankine and Pierre Henri Hugoniot independently developed

15946-495: The system, so there was no clutch pedal. From 1957 the ID19 model offered a simplified hydraulic system, with manual steering and conventional manual gearshift, and a significant price reduction. From 1968, with revised front end style, the DS also introduced auxiliary driving lights, that moved directionally with the steering, improving visibility at night. Production from 1956 to 1975 totalled almost 1.5 million cars. The streamlined car

16080-446: The theory for flow properties before and after a shock wave , while Jakob Ackeret led the initial work of calculating the lift and drag of supersonic airfoils. Theodore von Kármán and Hugh Latimer Dryden introduced the term transonic to describe flow speeds between the critical Mach number and Mach 1 where drag increases rapidly. This rapid increase in drag led aerodynamicists and aviators to disagree on whether supersonic flight

16214-478: The time, even on its narrow tires (factory-mounted Michelin ZX 145SR15). Its central hydraulic system, powering the four disc brakes (inboard in front to help lower unsprung weight) and the advanced hydro-pneumatic self-levelling suspension , was derived from the Citroën DS . It also has a feature that increased or decreased braking pressure in accordance with cargo load, without any noticeable difference in

16348-580: The twin-headlight fixtures developed for export markets on their GSs (although never on the well-equipped Pallas model). Slovenian GSs were commonly finished in "campus beige" color. The GSA was called the GA in Yugoslavia. Between 1979 and 1983, around 5,500 were exported to East Germany making it one of the few western cars in the country. Erich Honecker , the East German party leader, also maintained

16482-535: The uprated 1,222 cc engine producing 48 kW achieved by using high compression pistons, round, rather than oval inlet manifolds, a Weber carburetor, and larger diameter driveshafts. A variant of the X2 marketed in Europe, it featured special wheel trim, twin stripes along the sides incorporating an X2 emblem on the front fenders, a rear spoiler, a rear window louvre, and four round headlights mounted in black plastic housings. All three body-styles, GS and GSA versions and

16616-717: The war with the rank of captain. He was also courageous, having been decorated with the Military Cross and the Legion of Honour. He started working for Michelin in 1918, reporting directly to Édouard Michelin , co-director and founder of the business. Boulanger joined the Michelin board in 1922 and became president of Citroën in January 1938 after the death in a road accident of his friend Pierre Michelin remaining in this position until his own death in 1950. In 1938, he also had become Michelin's joint managing director. During

16750-450: The war, however, he realized that unless he planned ahead he would have a modern factory without a product. Citroën was already experienced in the automotive business, thanks to a successful six-year stint working with Mors between 1908 and the outbreak of war . The decision to switch to automobile manufacturing was taken as early as 1916, which is the year when Citroën asked the engineer Louis Dufresne, previously with Panhard , to design

16884-525: The work of Aristotle and Archimedes . In 1726, Sir Isaac Newton became the first person to develop a theory of air resistance, making him one of the first aerodynamicists. Dutch - Swiss mathematician Daniel Bernoulli followed in 1738 with Hydrodynamica in which he described a fundamental relationship between pressure, density, and flow velocity for incompressible flow known today as Bernoulli's principle , which provides one method for calculating aerodynamic lift. In 1757, Leonhard Euler published

17018-509: Was a common sight on French roads until recently; 9 million 2CV variants were produced in the period 1948–1990. 1955 saw the introduction of the DS , the first full usage of Citroën's hydropneumatic self-levelling suspension system, tested on the rear suspension of the Traction in 1954. The DS was also the first production car with modern disc brakes . A single high-pressure hydraulic system

17152-494: Was a serious flaw with the plan particularly for companies producing engines with high fuel consumption. In 1974, the carmaker withdrew from North America due to U.S. design regulations that outlawed core features of Citroën cars (see Citroën SM ). Huge losses at Citroën were caused by the failure of the Comotor rotary engine venture added to the strategic management error of going the 15 years from 1955 to 1970 without

17286-490: Was achievable until the sound barrier was broken in 1947 using the Bell X-1 aircraft. By the time the sound barrier was broken, aerodynamicists' understanding of the subsonic and low supersonic flow had matured. The Cold War prompted the design of an ever-evolving line of high-performance aircraft. Computational fluid dynamics began as an effort to solve for flow properties around complex objects and has rapidly grown to

17420-469: Was facelifted in 1979 and given a hatchback , and renamed the GSA. This change reflected the growing sales of small family hatchbacks in Europe since the launch of the Volkswagen Golf . Revisions included the grille, plastic bumpers, taillights, hubcaps and exterior door handles. It also had a revised dashboard with the auxiliary controls on column-shaped pods so they could be reached without moving

17554-447: Was raised to 164 km/h (102 mph) for both long and short gearbox ratios). The GS and GSA needed full use of the free-revving engines to maintain progress, except when cruising, in the tradition of the Citroën 2CV . The four-wheel independent suspension featured a double wishbone layout at the front and trailing arms at the rear. Both axles comprised rigid sub frames that gave the car unmatched ride quality and road holding for

17688-489: Was remarkable for its era and had a remarkable sounding name – in French, DS is pronounced [de.ɛs] , which sounds the same as déesse , which means Goddess . It placed third in the 1999 Car of the Century competition. This high-pressure hydraulic system would form the basis of over 9 million Citroën cars, including the DS , SM , GS , CX , BX , XM , Xantia , C5 , and C6 . Self-levelling suspension

17822-577: Was sacked by the French Resistance , his name was prominent on a Nazi blacklist of the most important enemies of the Reich, to be arrested in the event of an allied invasion of France. Citroën researchers, including Paul Magès , continued their work in secret, against the express orders of the Germans, and developed the concepts that were later brought to market in three remarkable vehicles –

17956-420: Was used to actuate the power steering , the suspension and brakes; the brakes were fully powered, not power assisted, as pedal force was not a component of braking power. The gearshift, (semi- automatic transmission ) was also powered by the hydraulic system through a control valve, with actuating pistons in the gearbox cover to shift the gears in the transmission , and the clutch was operated automatically by

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