- Ground effect in cars
:"For another similarly named effect relating to aircraft, see
Ground effect in aircraft."
Ground effect is term applied to a series of aerodynamic effects used in car design, which has been exploited to create
downforce, particularly in racing cars. This has been the successor to the earlier dominant aerodynamic theory of streamlining. Champ Carsemployed ground effect to some extent, but Formula Oneand most other racing series' worldwide currently use design constraints to heavily limit its effectiveness.
In racing cars, a designer's aim is for increased downforce, allowing greater cornering speeds. (Starting in the mid 1960s 'wings', or inverted aerofoils, were routinely used in the design of racing cars to increase downforce, but this is "not" ground effect.) This kind of ground effect is easily illustrated by taking a
tarpaulinout on a windy day and holding it close to the ground, it can be observed that when close enough to the ground the tarp will suddenly be sucked towards the ground.
However, substantial further downforce is available by understanding the ground to be part of the aerodynamic system in question. The basic idea is to create an area of low
pressureunderneath the car, so that the higher pressure above the car will apply a downward force. Naturally, to maximize the force one wants the maximum area at the minimal pressure. Racing car designers have achieved low pressure in two ways: first, by using a fan to pull air out of the cavity; second, to design the underside of the car so that incoming air is accelerated through a narrow slot between the car and the ground, lowering pressure by Bernoulli's principle.
Jim Hall built Chaparral cars to both these principles. His 1961 car attempted to use the shaped underside method but there were too many other aerodynamic problems with the car for it to work properly. His 1966 cars used a dramatic high wing for their downforce. His
Chaparral 2J"sucker car" of 1970 was revolutionary. It had two fans at the rear of the car driven by a dedicated two-strokeengine; it also had "skirts", which left only a minimal gap between car and ground, to seal the cavity from the atmosphere. Although it did not win a race, some competition had lobbied for its ban, which came into place at the end of that year. Movable aerodynamic devices were banned from most branches of the sport.Harvnb|Nye|1985|p=94] Formula Onewas the next setting for ground effect in racing cars. Several Formula One designs came close to the ground effect solution which would eventually be implemented by Lotus. In 1968 and 1969, Tony Ruddand Peter Wright at British Racing Motors(BRM) experimented on track and in the wind tunnel with long aerodynamic section side panniers to clean up the turbulent airflow between the front and rear wheels. Both left the team shortly after and the idea was not taken further. Robin Herd at March Engineering, on a suggestion from Wright, used a similar concept on the 1970 March Formula One car. In both cars the sidepods were too far away from the ground for significant ground effect to be generated, and the idea of sealing the space under the wing section to the ground had not yet been developed.
On a different tack, Brabham designer Gordon Murray used air dams at the front of his
Brabham BT44s in 1974 to exclude air from flowing under the vehicle. Upon discovering that these tended to wear away with the pitching movement of the car, he placed them further back and discovered that a small area of negative pressure was formed under the car, generating a useful amount of downforce - around 150lbs. McLaren produced similar underbody details for their McLaren M23 design.In 1977 Rudd and Wright, now at Lotus, developed the Lotus 78'wing car', based on a concept from Lotus owner and designer Colin Chapman. Its sidepods, bulky constructions between front and rear wheels, were shaped as inverted aerofoils and sealed with flexible "skirts" to the ground. The design of the radiators, embedded into the sidepods, was partly based on that of the De Havilland Mosquito. [Harvnb|Nye|1985|p=96] The team won 5 races that year, and 2 in 1978 while they developed the much improved Lotus 79. The most notable contender in 1978 was the BrabhamBT46B Fancar, designed by Gordon Murray. Its fan, spinning on a horizontal, longitudinal axis at the back of the car, took its power from the main gearbox. The car avoided the sporting ban by claims that the fan's main purpose was for engine cooling as less than 50% of the airflow was used to create a depression under the car. It raced just once, with Niki Laudawinning at the Swedish Grand Prix. The car's supreme advantage was proven after the track became oily. While other cars had to slow, Lauda was able to accelerate over the oil due to the tremendous downforce, which rose with engine speed. [Harvnb|Nye|1985|p=130] The car was also observed to visibly squat when the engine was revved at a standstill, and could survive a 10,000rpm clutch drop in 1st gear with no wheelspin. [ [http://www.forix.com/8w/fancar.html 8W - Why? - Brabham BT46B ] ] Brabham's owner, Bernie Ecclestone, who had recently become president of the Formula One Constructors Association, reached an agreement with other teams to withdraw the car after three races. However the Fédération Internationale de l'Automobile(FIA), governing body of Formula One and many other motor sports, decided to ban 'fan cars' with almost immediate effect. [Harvnb|Henry|1985|p=186-187] The Lotus 79, on the other hand, went on to win 6 races and the world championship for Mario Andrettiand gave team-mate Ronnie Petersona posthumous second place, demonstrating just how much of an advantage the cars had. In following years other teams copied and improved on the Lotus until cornering speeds became dangerously high, resulting in several severe accidents in 1982 (most notably the death of Gilles Villeneuve), flat undersides became mandatory for 1983. [Harvnb|Nye|1985|p=33] Part of the danger of relying on ground effects to corner at high speeds is the possibility of the sudden removal of this force; if the belly of the car contacts the ground, the flow is constricted too much, resulting in almost total loss of any ground effects. If this occurs in a corner where the driver is relying on this force to stay on the track, its sudden removal can cause the car to abruptly lose most of its traction and skid off the track.
The effect was used in its most effective form in
Champ Cardesigns. Racing series based in Europe have mainly followed the lead of Formula One and mandated flat undersides for their cars. This heavily constrains the degree to which ground effect can be generated. Nonetheless, as of 2007, Formula One cars still generate a proportion of their overall downforce by this effect, vortices generated at the front of the car are used to seal the gap between the sidepods and the track and a small diffuser is permitted behind the rear wheel centerline to re-accelerate the high speed underbody airflow to free flow conditions. High nose designs, starting with the Tyrrell 019of 1990, optimize the airflow conditions at the front of the car.Fact|date=February 2007
Note that while such downforce-producing aerodynamic techniques are often referred to with the catch-all term "ground effect", they are not strictly speaking a result of the same aerodynamic phenomenon as the ground effect which is apparent in aircraft at very low
Porpoising is a term that was commonly used to describe a particular fault encountered in ground effect racing cars.
Racing cars had only been using their bodywork to generate downforce for just over a decade when
Colin Chapman's Lotus 78and 79 cars demonstrated that ground effect was the way to go in Formula One, so naturally at this point under-car aerodynamics were still very poorly understood. To compound this problem the teams that were keenest to pursue ground effects tended to be the more poorly-funded British "garagiste" teams, who had little money to spare for wind tunnel testing and tended simply to mimic the front-running Lotuses.
This led to a generation of cars that were designed as much by hunch as by any great knowledge of the finer details, making them extremely pitch sensitive. As the centre of pressure on the sidepod aerofoils moved about depending on the car's speed, attitude and ground clearance, these forces interacted with the car's suspension systems and cars began to resonate, particularly at slow speeds, rocking back and forth - sometimes quite violently. Some drivers were even known to complain of sea-sickness... This back-and-forth rocking motion, like a
porpoisediving into and out of the sea as it swims along at speed, is what gives the phenomenon its name.
Ground effects were largely banned from Formula One in the early 1980s, but Group C sportscars and other racing cars continued to suffer from porpoising until gradually better knowledge of ground effects allowed designers to minimise the problem.
Ground effects(Aerodynamic body pieces)
Ground effect in aircraft
Formula One car
* Harvard reference
Title=Brabham, the Grand Prix Cars
* Harvard reference
Title=Autocourse History of the Grand Prix car 1966 - 1985
* [http://www.photoessayist.com/canam/chaparral/index.html Photoessayist.com: The Chaparral 2J]
* [http://www.vintagerpm.com/chaparral_history.htm VintageRPM: Chaparral history]
* [http://8w.forix.com/fancar.html 8W: Brabham-Alfa BT46B "fan car"]
* [http://www.ddavid.com/formula1/lotus79.htm Dennis David: Lotus 79]
Wikimedia Foundation. 2010.
См. также в других словарях:
Ground effect — may refer to:* Ground effect in aircraft, mostly related to aerodynamic lift * Ground effect in cars, an effect that creates downforce, primarily in racing cars … Wikipedia
Ground effect in aircraft — Aircraft may be affected by a number of ground effects, aerodynamic effects due to a flying body s proximity to the ground.One of the most important of these effects is the Wing In Ground effect, which refers to the reduction in drag experienced… … Wikipedia
Effect of the Siege of Leningrad on the city — Timeline of the Siege of Leningrad 1941 *June 22: Operation Barbarossa begins. *June 29: Evacuation of children and women from Leningrad starts. *June–July: Over 300 thousand civilian refugees from Pskov and Novgorod manage to escape from the… … Wikipedia
Chaparral Cars — Joakim Bonnier 1966 in the Chaparral 2D during practice at the Nürburgring … Wikipedia
Chevron Cars Ltd — This article is about the manufacturer of racing cars, for the Chevron promotional cartoon see Chevron Cars. Chevron Cars Ltd. is a manufacturer of racing cars, founded by Derek Bennett in 1965. Following Bennett s death in 1978, the firm has… … Wikipedia
Tony Rudd — Antony Cyril Tony Rudd (March 18, 1923 August 22, 2003) was an engineer involved in aero engine design and motor racing, with particular associations with BRM and Lotus. Early life and war service Rudd became involved with motor racing in the… … Wikipedia
Downforce — Three different styles of front wings from three different Formula One eras, all designed to produce downforce at the front end of the respective race cars. Top to bottom: Ferrari 312 (1979), Lotus 79 (1978), McLaren MP4 10 (1995) Downforce is a… … Wikipedia
Automotive aerodynamics — forces at high speeds. For some classes of racing vehicles, it may also be important to produce desirable downwards aerodynamic forces to improve traction and thus cornering abilities.An aerodynamic automobile will integrate the wheel arcs and… … Wikipedia
Diffuser (automotive) — Top: Lateral view; the red circles mark the front air dam/splitter and rear diffuser. Bottom: Underbody view. A diffuser, in an automotive context, is a shaped section of the car underbody which improves the car s aerodynamic properties by… … Wikipedia
History of Formula One — Formula One has its roots in the European Grand Prix motor racing ( q.v. for pre 1947 history) of the 1920s and 1930s. However, the foundation of Formula One began in 1946 with the Fédération Internationale de l Automobile s (FIA s)… … Wikipedia