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{{Short description|Aerodynamic principle}}
{{distinguish|Ground effects}}
In car design, '''ground effect''' is a series of effects which have been exploited in ] to create ], particularly in racing cars. This has been the successor to the earlier dominant aerodynamic focus on ]. The international ] series and American racing ] employ ground effects in their engineering and designs. Similarly, they are also employed in other racing series to some extent; however, across Europe, many series employ regulations (or complete bans) to limit its effectiveness on safety grounds.


⚫ ==Theory==
:''For another similarly named effect relating to aircraft, see ].''
In racing cars, a designer's aim is for increased downforce and grip to achieve higher cornering speeds. A substantial amount of downforce is available by understanding the ground to be part of the aerodynamic system in question, hence the name "ground effect". Starting in the mid-1960s, ] were routinely used in the design of race cars to increase downforce (which is not a type of ground effect). Designers shifted their efforts at understanding air flow around the perimeter, body skirts, and undersides of the vehicle to increase downforce with less drag than compared to using a wing.


This kind of ground effect is easily illustrated by taking a ] out 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 be drawn towards the ground. This is due to ]; as the tarp gets closer to the ground, the cross sectional area available for the air passing between it and the ground shrinks. This causes the air to accelerate and as a result pressure under the tarp drops while the pressure on top is unaffected, and together this results in a net downward force. The same principles apply to cars.
'''Ground effect''' is term applied to a series of aerodynamic effects used in car design, which has been exploited to create ], particularly in racing cars. This has been the successor to the earlier dominant aerodynamic theory of streamlining. ] employed ground effect to some extent, but ] and most other racing series' worldwide currently use design constraints to heavily limit its effectiveness.


The Bernoulli principle is not the only aspect of mechanics in generating ground-effect downforce. A large part of ground-effect performance comes from taking advantage of ]. In the tarp example above, neither the tarp nor the ground is moving. The ] between the two surfaces works to slow down the air between them which lessens the Bernoulli effect. When a car moves over the ground, the boundary layer on the ground becomes helpful. In the reference frame of the car, the ground is moving backwards at some speed. As the ground moves, it pulls on the air above it and causes it to move faster.{{dubious|date=June 2023|reason="The air is not moving relative to ground, only the car is. So in the reference frame of the car, the air is already moving, with or without the ground 'pulling' on it."}} This enhances the Bernoulli effect and increases downforce. It is an example of ].
⚫ ==Theory==
In racing cars, a designer's aim is for increased downforce, allowing greater cornering speeds. (Starting in the mid 1960s 'wings', or inverted ]s, 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 ] out 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.


⚫ 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 ] which is apparent in aircraft at very low ].
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 ] underneath 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 ].


==History== ==History==
]
⚫ ] built ] 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 ] "sucker car" of 1970 was revolutionary. It had two fans at the rear of the car driven by a dedicated ] engine; 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.<ref name="Ground Effects">{{Harvnb|Nye|1985|p=94}}</ref>
]
⚫ American ] developed and built his ] cars around the principles of ground effects, pioneering them. 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 ] "sucker car" of 1970 was revolutionary. It had two fans at the rear of the car driven by a dedicated ] engine; 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.<ref name="Ground Effects2">{{Harvnb|Nye|1985|p=94}}</ref>


In 1968, the ] designer and engineer, ], developed the ] for the ] category,<ref>{{Cite web |last=Automundo |first=Viejas |date=8 April 2013 |title=Viejas Automundo: Revista Automundo Nº 154 - 16 Abril 1968 |url=http://viejasautomundo.blogspot.com/2013/04/revista-automundo-n-154-16-abril-1968.html |access-date=2024-04-17 |website=Viejas Automundo}}</ref> making its first appearance in ] for the 1969 season with ] and ] as drivers.
⚫ ] was 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, ] and ] at ] (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 ], 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.<ref name="Ground Effects" />


During 1968, a 1/5 scale model was made, which was tested in the wind tunnel of the ] usually employed by the ], demonstrating the functionality of the ground effect at that scale. In 2023, the Pronello Huayra chassis #002 was invited to the ]. During its stay in ], the car was taken to the ], where a complete aerodynamic analysis was carried out by the argentine engineer and professor ].
⚫ On a different tack, Brabham designer Gordon Murray used air dams at the front of his ]s 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.<ref name="Ground Effects" />
⚫ ]
⚫ In 1977 Rudd and Wright, now at Lotus, developed the ] 'wing car', based on a concept from ] owner and designer ]. 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 ].<ref>{{Harvnb|Nye|1985|p=96}}</ref> The team won 5 races that year, and 2 in 1978 while they developed the much improved ]. The most notable contender in 1978 was the ] ] Fancar, designed by ]. 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 ] winning 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.<ref>{{Harvnb|Nye|1985|p=130}}</ref> 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.<ref></ref> Brabham's owner, ], who had recently become president of the ], reached an agreement with other teams to withdraw the car after three races. However the ] (FIA), governing body of Formula One and many other motor sports, decided to ban 'fan cars' with almost immediate effect.<ref>{{Harvnb|Henry|1985|p=186-187}}</ref> The Lotus 79, on the other hand, went on to win 6 races and the world championship for ] and gave team-mate ] a 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 ]), flat undersides became mandatory for 1983.<ref>{{Harvnb|Nye|1985|p=33}}</ref> 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.


''"We always thought it had ground effect... When Heriberto tested it at the National University of Córdoba, he verified its air resistance with a 1/5 scale model that was perfect, without door and hood openings, without the intake turrets..."'' Rinland said.<ref>{{Cite web |last=Autocosmos |date=2023-07-17 |title=Pronello Huayra Ford: el primer auto de competición con efecto suelo del mundo |url=https://noticias.autocosmos.com.ar/2023/07/17/pronello-huayra-ford-el-primer-auto-de-competicion-con-efecto-suelo-del-mundo |access-date=2024-04-17 |website=Autocosmos |language=es-AR}}</ref>
The effect was used in its most effective form in ] designs. Racing series based in Europe and Australia 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, ] 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 ] of 1990, optimize the airflow conditions at the front of the car.{{Fact|date=February 2007}}


''“The tests we did in the ] demonstrated its great aerodynamic efficiency: we obtained a Cx 0.25 with the short tail and a Cx 0.23 with the long tail, which it used on the fastest circuits. Almost, almost what Heriberto had measured at the time”''<ref>{{Cite web |date=2023-07-16 |title=Pronello Huayra Ford: el primer auto de competición con efecto suelo del mundo |url=https://automundo.com.ar/pronello-huayra-ford-efecto-suelo-catesby-tunnel-2023/ |access-date=2024-04-17 |website=AUTOMUNDO |language=es-AR}}</ref>
⚫ Note that while such downforce-producing aerodynamic techniques are often referred to with the catch-all term "]", they are not strictly speaking a result of the same aerodynamic phenomenon as the ground effect which is apparent in aircraft at very low ]s.


'''“'''It has a slippery upper shape and a flat floor with a ] that gave it quite an edge in its day. The diffuser has an expansion ratio that puts it staggeringly close to the maximum ] you can get from a diffuser. The car was at the tunnel with pressure tapings added to it, in order to look at the pressure distribution around the car which looks to completely confirm that it works exactly as the designer expected.”, explained ]. These tests were carried out with and without the "long tail" which was used for high-speed circuits, with the vehicle propelled by its own means, at working temperature, returning consistent and repeatable results.<ref>{{Cite web |last=Brook-Jones |first=Callum |date=2023-07-26 |title=Huayra Pronello-Ford tested in Catesby Tunnel ahead of Goodwood FOS |url=https://www.automotivetestingtechnologyinternational.com/news/aerodynamics/huayra-pronello-ford-tested-in-catesby-tunnel-ahead-of-goodwood.html |access-date=2024-04-17 |website=Automotive Testing Technology International |language=en-GB}}</ref><ref>{{Cite web |title=Huayra Pronello Ford: Argentinian sensation {{!}} Classic & Sports Car |url=https://www.classicandsportscar.com/features/huayra-pronello-ford-argentinian-sensation |access-date=2024-04-17 |website=www.classicandsportscar.com}}</ref>
⚫ ==Porpoising==
]
Porpoising is a term that was commonly used to describe a particular fault encountered in ground effect racing cars.
]
⚫ ] was 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, ] and ] at ] (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 ], 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.<ref name="Ground Effects2" />


At about the same time, Shawn Buckley began his work in 1969 at the ] on undercar aerodynamics sponsored by ], founder of Formula One ]. Buckley had previously designed the first high wing used in an ], Jerry Eisert's "Bat Car" of the ]. By proper shaping of the car's underside, the air speed there could be increased, lowering the pressure and pulling the car down onto the track. His test vehicles had a ]-like channel beneath the cars sealed by flexible side skirts that separated the channel from above-car aerodynamics. He investigated how flow separation on the undersurface channel could be influenced by boundary layer suction and divergence parameters of the underbody surface.<ref>S. Buckley, "Vehicle Surface Interaction" Ph.D. Dissertation, University of California - Berkeley, Sept., 1972</ref><ref>B. Shawn Buckley, "Road Test Aerodynamic Instrumentation", SAE paper 741030, 1974-02-01</ref><ref>B. Shawn Buckley, Edmund V. Laitone, "Air Flow Beneath an Automobile", SAE paper 741028, 1974-02-01</ref> Later, as a mechanical engineering professor at ], Buckley worked with Lotus developing the ].
⚫ Racing cars had only been using their bodywork to generate downforce for just over a decade when ]'s ] and ] 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.


⚫ On a different tack, Brabham designer ] used air dams at the front of his ] 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 {{convert|150|lbs|abbr=on|disp=flip|sigfig=1}}. McLaren produced similar underbody details for their McLaren M23 design.<ref name="Ground Effects2" />
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 ] diving into and out of the sea as it swims along at speed, is what gives the phenomenon its name.
⚫ ] used a large fan to reduce underbody air pressure.]]
⚫ In 1977 Rudd and Wright, now at Lotus, developed the ] 'wing car', based on a concept from Lotus owner and designer ]. 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 ] aircraft.<ref>{{Harvnb|Nye|1985|p=96}}</ref> The team won five races that year, and two in 1978 while they developed the much improved ]. The most notable contender in 1978 was the ]-] ] 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 ] winning at the ]. The car's 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.<ref>{{Harvnb|Nye|1985|p=130}}</ref> The car was also observed to squat when the engine was revved at a standstill.<ref></ref> Brabham's owner, ], who had recently become president of the ], reached an agreement with other teams to withdraw the car after three races. However the ] (FIA), governing body of Formula One and many other motorsport series, decided to ban 'fan cars' with almost immediate effect.<ref>{{Harvnb|Henry|1985|pp=186–187}}</ref> The Lotus 79, on the other hand, went on to win six races and the world championship for ] and gave teammate ] a posthumous second place, demonstrating just how much of an advantage the cars had. In the following years other teams copied and improved on the Lotus until cornering speeds became dangerously high, resulting in several severe accidents in ]; flat undersides became mandatory for 1983.<ref>{{Harvnb|Nye|1985|p=33}}</ref> 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 underside 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.


After a forty-year ban, ground effect returned to Formula 1 in 2022 under the latest set of regulation changes.
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.

The effect was used in its most effective form in ] designs. IndyCars did not use ground effect as substantially as Formula One. For example, they lacked the use of skirts to seal off the underbody of the car. IndyCars also rode higher than ground effect F1 cars and relied on wings for significant downforce as well, creating an effective balance between over the car downforce and ground effect.

⚫ ==Porpoising==
⚫ "Porpoising" is a term 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 ]'s ] and ] cars demonstrated that ground effect was the future in Formula One, so, at this point, under-car aerodynamics were still very poorly understood. To compound this problem the teams that were very keen to pursue ground effects tended to be the more poorly funded British "garagista" teams, who had little money to spare for wind tunnel testing, and tended simply to mimic the front-running Lotuses (including the ] and ] teams).{{Citation needed|date=March 2010}}

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 the cars began to resonate, particularly at slow speeds, rocking back and forth - sometimes quite violently. Some drivers were known to complain of sea-sickness.{{Citation needed|date=March 2010}} This rocking motion, like a ] diving into and out of the sea as it swims at speed, gives the phenomenon its name. These characteristics, combined with a rock-hard suspension, resulted in the cars giving an extremely unpleasant ride. Ground effects were largely banned from Formula One in the early 1980s until 2022, but Group C sportscars and other racing cars continued to suffer from porpoising until better knowledge of ground effects allowed designers to minimise the problem.<ref name="elleray2">{{Cite web |last=Elleray |first=Peter |title=Mulsanne's Corner: Peter Elleray on the Bentley LMGTP |url=http://www.mulsannescorner.com/bentleyelleray.html |access-date=2017-10-21 |website=Mulsanne's Corner}}</ref> At the first pre-season test in Barcelona ahead of the ], ] said extreme porpoising could lead to safety issues and later stated he was suffering from chest pain due to extreme porpoising during the ]. At the ], ] struggled to get out of the car after the race due to violent porpoising.<ref>{{cite web |last1=Mitchell |first1=Scott |date=24 February 2022 |title=F1 2022 car porpoising 'safety concern' at its worst |url=https://the-race.com/formula-1/f1-2022-car-porpoising-a-safety-concern-at-its-worst/#disqus_thread |access-date=24 February 2022 |website=The Race |publisher=The Race Media}}</ref><ref>{{Cite web |date=2022-04-25 |title=George Russell reveals chest pain from Mercedes porpoising at Emilia Romagna GP |url=https://www.independent.co.uk/f1/george-russell-mercedes-chest-pain-porpoising-imola-b2064898.html |access-date=2022-04-27 |website=The Independent |language=en}}</ref>


==See also== ==See also==

*]
*] * ]
* ]
*] (Aerodynamic body pieces)
* ]
*]
*] * ]
*] * ]


==References== ==References==
{{reflist|2}} {{reflist|2}}


* {{Citation |surname1=Henry |given1=Alan |title=Brabham, the Grand Prix Cars |year=1985 |publisher=Osprey |isbn=0-905138-36-8}}
* {{Harvard reference
* {{Citation |surname1=Nye |given1=Doug |title=Autocourse History of the Grand Prix car 1966–1985 |year=1985 |publisher=Hazleton publishing |isbn=0-905138-37-6}}
| Surname1=Henry

| Given1=Alan
⚫ ==External links==
| Year=1985
| Title=Brabham, the Grand Prix Cars
| Publisher=Osprey
| ID=ISBN 0-905138-36-8
| URL=
| Access-date=
}}
* {{Harvard reference
| Surname1=Nye
| Given1=Doug
| Year=1985
| Title=Autocourse History of the Grand Prix car 1966 - 1985
| Publisher=Hazleton publishing
| ID=ISBN 0-905-138-37-6
| URL=
| Access-date=
}}


⚫ == External links ==
* *
* * {{Webarchive|url=https://web.archive.org/web/20141226044211/http://www.vintagerpm.com/can-am-history-of-chaparral/ |date=2014-12-26 }}
* *
* * {{Webarchive|url=https://web.archive.org/web/20110605093433/http://www.ddavid.com/formula1/lotus79.htm|date=2011-06-05}}
{{DEFAULTSORT:Ground Effect (Cars)}}

]
]
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Latest revision as of 17:29, 27 November 2024

Aerodynamic principle

In car design, ground effect is a series of effects which have been exploited in automotive aerodynamics to create downforce, particularly in racing cars. This has been the successor to the earlier dominant aerodynamic focus on streamlining. The international Formula One series and American racing IndyCars employ ground effects in their engineering and designs. Similarly, they are also employed in other racing series to some extent; however, across Europe, many series employ regulations (or complete bans) to limit its effectiveness on safety grounds.

Theory

In racing cars, a designer's aim is for increased downforce and grip to achieve higher cornering speeds. A substantial amount of downforce is available by understanding the ground to be part of the aerodynamic system in question, hence the name "ground effect". Starting in the mid-1960s, 'wings' were routinely used in the design of race cars to increase downforce (which is not a type of ground effect). Designers shifted their efforts at understanding air flow around the perimeter, body skirts, and undersides of the vehicle to increase downforce with less drag than compared to using a wing.

This kind of ground effect is easily illustrated by taking a tarpaulin out 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 be drawn towards the ground. This is due to Bernoulli's principle; as the tarp gets closer to the ground, the cross sectional area available for the air passing between it and the ground shrinks. This causes the air to accelerate and as a result pressure under the tarp drops while the pressure on top is unaffected, and together this results in a net downward force. The same principles apply to cars.

The Bernoulli principle is not the only aspect of mechanics in generating ground-effect downforce. A large part of ground-effect performance comes from taking advantage of viscosity. In the tarp example above, neither the tarp nor the ground is moving. The boundary layer between the two surfaces works to slow down the air between them which lessens the Bernoulli effect. When a car moves over the ground, the boundary layer on the ground becomes helpful. In the reference frame of the car, the ground is moving backwards at some speed. As the ground moves, it pulls on the air above it and causes it to move faster. This enhances the Bernoulli effect and increases downforce. It is an example of Couette flow.

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 altitudes.

History

Pronello Huayra-Ford, in its long tail, high speed configuration
Pronello Huayra-Ford

American Jim Hall developed and built his Chaparral cars around the principles of ground effects, pioneering them. 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-stroke engine; 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.

In 1968, the argentine designer and engineer, Heriberto Pronello, developed the Pronello Huayra-Ford for the Sport Prototipo Argentino category, making its first appearance in Córdoba for the 1969 season with Carlos Reutemann and Carlos Pascualini as drivers.

During 1968, a 1/5 scale model was made, which was tested in the wind tunnel of the Fábrica Militar de Aviones (FMA) usually employed by the Argentine Air Force, demonstrating the functionality of the ground effect at that scale. In 2023, the Pronello Huayra chassis #002 was invited to the Goodwood Festival Of Speed. During its stay in England, the car was taken to the Catesby tunnel, where a complete aerodynamic analysis was carried out by the argentine engineer and professor Sergio Rinland.

"We always thought it had ground effect... When Heriberto tested it at the National University of Córdoba, he verified its air resistance with a 1/5 scale model that was perfect, without door and hood openings, without the intake turrets..." Rinland said.

“The tests we did in the Catesby Tunnel demonstrated its great aerodynamic efficiency: we obtained a Cx 0.25 with the short tail and a Cx 0.23 with the long tail, which it used on the fastest circuits. Almost, almost what Heriberto had measured at the time”

“It has a slippery upper shape and a flat floor with a diffuser that gave it quite an edge in its day. The diffuser has an expansion ratio that puts it staggeringly close to the maximum downforce you can get from a diffuser. The car was at the tunnel with pressure tapings added to it, in order to look at the pressure distribution around the car which looks to completely confirm that it works exactly as the designer expected.”, explained Willem Toet. These tests were carried out with and without the "long tail" which was used for high-speed circuits, with the vehicle propelled by its own means, at working temperature, returning consistent and repeatable results.

Chaparral 2J at Goodwood historic
Rear of Chaparral 2J with large dual suction fan exhausts

Formula One was 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 Rudd and 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.

At about the same time, Shawn Buckley began his work in 1969 at the University of California, Berkeley on undercar aerodynamics sponsored by Colin Chapman, founder of Formula One Lotus. Buckley had previously designed the first high wing used in an IndyCar, Jerry Eisert's "Bat Car" of the 1966 Indianapolis 500. By proper shaping of the car's underside, the air speed there could be increased, lowering the pressure and pulling the car down onto the track. His test vehicles had a Venturi-like channel beneath the cars sealed by flexible side skirts that separated the channel from above-car aerodynamics. He investigated how flow separation on the undersurface channel could be influenced by boundary layer suction and divergence parameters of the underbody surface. Later, as a mechanical engineering professor at MIT, Buckley worked with Lotus developing the Lotus 78.

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 70 kg (150 lb). McLaren produced similar underbody details for their McLaren M23 design.

Brabham-Alfa's BT46B used a large fan to reduce underbody air pressure.

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 aircraft. The team won five races that year, and two in 1978 while they developed the much improved Lotus 79. The most notable contender in 1978 was the Brabham-Alfa Romeo BT46B 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 Lauda winning at the 1978 Swedish Grand Prix. The car's 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. The car was also observed to squat when the engine was revved at a standstill. 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 motorsport series, decided to ban 'fan cars' with almost immediate effect. The Lotus 79, on the other hand, went on to win six races and the world championship for Mario Andretti and gave teammate Ronnie Peterson a posthumous second place, demonstrating just how much of an advantage the cars had. In the following years other teams copied and improved on the Lotus until cornering speeds became dangerously high, resulting in several severe accidents in 1982; flat undersides became mandatory for 1983. 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 underside 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.

After a forty-year ban, ground effect returned to Formula 1 in 2022 under the latest set of regulation changes.

The effect was used in its most effective form in IndyCar designs. IndyCars did not use ground effect as substantially as Formula One. For example, they lacked the use of skirts to seal off the underbody of the car. IndyCars also rode higher than ground effect F1 cars and relied on wings for significant downforce as well, creating an effective balance between over the car downforce and ground effect.

Porpoising

"Porpoising" is a term 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 78 and 79 cars demonstrated that ground effect was the future in Formula One, so, at this point, under-car aerodynamics were still very poorly understood. To compound this problem the teams that were very keen to pursue ground effects tended to be the more poorly funded British "garagista" teams, who had little money to spare for wind tunnel testing, and tended simply to mimic the front-running Lotuses (including the Kauhsen and Merzario teams).

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 the cars began to resonate, particularly at slow speeds, rocking back and forth - sometimes quite violently. Some drivers were known to complain of sea-sickness. This rocking motion, like a porpoise diving into and out of the sea as it swims at speed, gives the phenomenon its name. These characteristics, combined with a rock-hard suspension, resulted in the cars giving an extremely unpleasant ride. Ground effects were largely banned from Formula One in the early 1980s until 2022, but Group C sportscars and other racing cars continued to suffer from porpoising until better knowledge of ground effects allowed designers to minimise the problem. At the first pre-season test in Barcelona ahead of the 2022 Formula One World Championship, George Russell said extreme porpoising could lead to safety issues and later stated he was suffering from chest pain due to extreme porpoising during the 2022 Emilia Romagna Grand Prix. At the 2022 Azerbaijan Grand Prix, Lewis Hamilton struggled to get out of the car after the race due to violent porpoising.

See also

References

  1. ^ Nye 1985, p. 94
  2. Automundo, Viejas (8 April 2013). "Viejas Automundo: Revista Automundo Nº 154 - 16 Abril 1968". Viejas Automundo. Retrieved 2024-04-17.
  3. Autocosmos (2023-07-17). "Pronello Huayra Ford: el primer auto de competición con efecto suelo del mundo". Autocosmos (in Spanish). Retrieved 2024-04-17.
  4. "Pronello Huayra Ford: el primer auto de competición con efecto suelo del mundo". AUTOMUNDO (in Spanish). 2023-07-16. Retrieved 2024-04-17.
  5. Brook-Jones, Callum (2023-07-26). "Huayra Pronello-Ford tested in Catesby Tunnel ahead of Goodwood FOS". Automotive Testing Technology International. Retrieved 2024-04-17.
  6. "Huayra Pronello Ford: Argentinian sensation | Classic & Sports Car". www.classicandsportscar.com. Retrieved 2024-04-17.
  7. S. Buckley, "Vehicle Surface Interaction" Ph.D. Dissertation, University of California - Berkeley, Sept., 1972
  8. B. Shawn Buckley, "Road Test Aerodynamic Instrumentation", SAE paper 741030, 1974-02-01
  9. B. Shawn Buckley, Edmund V. Laitone, "Air Flow Beneath an Automobile", SAE paper 741028, 1974-02-01
  10. Nye 1985, p. 96
  11. Nye 1985, p. 130
  12. 8W - Why? - Brabham BT46B
  13. Henry 1985, pp. 186–187
  14. Nye 1985, p. 33
  15. Elleray, Peter. "Mulsanne's Corner: Peter Elleray on the Bentley LMGTP". Mulsanne's Corner. Retrieved 2017-10-21.
  16. Mitchell, Scott (24 February 2022). "F1 2022 car porpoising 'safety concern' at its worst". The Race. The Race Media. Retrieved 24 February 2022.
  17. "George Russell reveals chest pain from Mercedes porpoising at Emilia Romagna GP". The Independent. 2022-04-25. Retrieved 2022-04-27.
  • Henry, Alan (1985), Brabham, the Grand Prix Cars, Osprey, ISBN 0-905138-36-8
  • Nye, Doug (1985), Autocourse History of the Grand Prix car 1966–1985, Hazleton publishing, ISBN 0-905138-37-6

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