“Ground Effect”. Its History and Theory explained

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Ground effect is a 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. IndyCars employ ground effect to some extent, but Formula One and most other racing series worldwide currently use design constraints to heavily limit its effectiveness.


Jim Hall built Chaparral 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 2 stroke; 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.

 sucker car

Formula 1 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 Univ. of California – Berkeley on undercar aerodynamics sponsored by Colin Chapman founder of F1 Lotus. Buckley had previously designed the first high wing used in an Indy 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 BT44sin 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 150 lbs. 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 aircraft.

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 Brabham 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 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. The car was also observed to visibly 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 (FOCA), reached an agreement with other teams to withdraw the car after three races. However the FIA 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 team-mate Ronnie Peterson 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; 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 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 IndyCar 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: 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 slow down the high speed underbody airflow to free-flow conditions. High nose designs, starting with the Tyrell 019 of 1990, optimize the airflow conditions at the front of the car.

The article is from Wikipedia: TJ13 would like to offer readers to contribute to our community by writing this kind of material. If interested contact thejudge13@hotmail.co.uk

Seeing as so many of you enjoyed Enrique yesterday, here his is again with simple tools of a water flow, a spoon, a flat surface, some paper and a pencil.  Former Williams and Ferrari Design Engineer, Enrique Scalabroni, looks at the aerodynamic phenomenon called ‘ground effect’ and how it generates more down force for the rear of the car.

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.

Other interesting material for you to consider. Here’s from beyond the grave Colin Chapman who some call the ‘father of ground effect’.

BBC Horizon’s explanations of ground effect with some historic context.


10 responses to ““Ground Effect”. Its History and Theory explained

  1. Enrico’s video is number 12 in a series of 12 on a youtube page . Several of the others are also QI. Is the Merc one real?
    Make tea first before you start to watch.
    It is humbling to realise that all that Enrico is explaining, is just background, taken for granted, before even you get to the starting point of designing anything in the slightest way aerodynamic.

  2. Amusing… or ironic… to see Bernie withdrawing his own Fan Car to keep his newly formed FOCA colleagues happy – in effect, did he sacrifice Gordon Murray for his own longer-term designs…?

  3. A few thoughts about the craft in the WIG video …

    The craft depicted look like a poor man’s Ekranoplan ….. 🙁

    And the ” Hoverwing ” design is in many ways a re-itteration of philosophy behind the SES ( Surface Effect Ship ) along with Lippisch’s Inverse Delta wing design.

    Both design’s from the 1960’s.

    As you said the term ” ground effect ” in aircraft wings is completely different from that in automotive terms.

    A better way of describing ground effect in aircraft or ekranoplans etc. is – compessibility. The term ground effect was used in aircraft because the effect was noticed near the ground, when air under the wings compressed to give increased lift.

    Whereas in cars it has more to do with the venturi effect, causing reduced pressure on the underside of the vehicle, relative to the upper surface.

    The ” bendy ” front wings that have appeared in recent years in F1 seem to use a combination of the traditional effect of an inverted wing along with some venturi effect.

    • Nice one mankyboy! Sparked up my memory of compression of fluids there, just enough to realize, erm. I never paid attention to those classes!

      I’m definitely liking the fact some of these discussions are showing up the talents of who knows Physics, and demonstrating who can explain what they mean. My last Physics tutor was a lady on secondment from RR Aero, in her sabbatical year. She had two qualities that were significant: the first I think stems from the fact that she had had to gain her way to seniority as a woman in the 70s and 80s, and as a result just could command attention with the simplicity of her explanations. I imagine she had to be superbly succinct to get through prejudices and office politics. The other was, erm, she was the hottest teacher we every had, and so 20 boys were hanging on her every word. I never regretted taking Maths and Physics as primaries. Pure and Applied Maths, at A Level, but I still suck at Pure – applied was something I could grasp far more easily. I cruised Applied and flunked Pure.

      I flunked from school, for many reasons, mostly personal. For years I had dreams of flaking a Physics exam. Literally woke up sweating, because to this day I have a real deficit on certain calculations. But flunking school was the reason I kept on learning. Our teacher instilled such a conceptual picture of the world as still is the foundation of much broader thought, and to this day, I think she actually made our class “get it” in ways that make me very jealous of that ability, and enrich my thinking two decades and more later.

      There’s obviously titles such as Race Car Engineering and many many others. Just so many trade magazines do so little to educate. That’s a gap I’ve tilted at a few times. If TJ13 with a little help, can time to time push this education deficit, I’d be overjoyed. Sommers, thanks man. But to the rest of you too long to list, it rocks my boat that we can drop in and out of this kind of discussion.

      I define education deficit not as a question of expenditure, or even nurture, let alone being force fed OC/Cam board A level papers at 13, but instead the paucity of discussion in real life. My parents talked about banking and finance all day. There you have a reason I was inured to that. The most essential thing in learning, is exposure to discussion, and yet when I flit about online, there are so few people who can convey what they mean, illustrate with their words, invite a passer by to partake of a debate.

      The sheer privilege of my own education embarrassed me at a very early age. I’ll never cogently argue that that had no effect on my decision to drop out, and find the real world. which – quelle surprise – I found rather harsh. I have been known to get bitter, in a bad week, how easily I might have had things in life. The absolute expectation, fait accomplis from age 12, that I would have a high flying academic or managerial career, will haunt me to my grave. As will the tears my father shed when he thought he’d done something wrong. Far from it, he’d done everything right. The intensity was a bit much for a teenager to deal with, and that’s why ever since I sought to learn other ways of teaching. Or rather instilling a urge in others to learn. I cruised so easily through early academia that I became a plain tearaway. I’ve deep ambitions to counteract the idea that good education in the mass is not taking a random lucky few starving intellects to the scholastic Ritz. If you guys can do anything – or just keep on, it feels the right direction – that helps my ideal of wider education, then consider me your loyal servant.

      My company is 18 this year, so it’s looking forward to being able to vote in the world! It may even get its drivers license, if I am generous. It’s still a stroppy, spotty, ineptly amorous thing unsure of its missteps and advances, snatching a kiss here and there and occasionally acting like a a dog humping your leg. But the aim is to bring trade and niche publications into the lives of who is learning. To do so required not being a slouch at this commerce thing, nor slacking at any aspect of that.

      I hope TJ allows this, because I’ve a ambition beyond merely commenting, but to solve a array of commercial problems that afflict publishers of all kinds when they try to strike out and illuminate the world they know and see. I guess you can say I have my reasons, to dedicate time to projects I think have potential. I’ve no intent to hijack anything, but when I read good commentary, I feel a little twitch in my spine that makes me feel good. The more people contribute, explain to others, add more than a “simple” discussion, the more I’m happy.

      Please everyone, read the TJ13 manifesto, and consider how you can be involved, passively or practically, to help find ways that as the project scales, we may capture hearts and minds, and above all young minds. To me, this place is a gift. Not a soap box, but something that aligns with my better instincts and desires. I think that could be a truism for everyone here, id we each allow ourselves to be mindful of what our own ambitions would be if we wanted the best outcome from a “mere” website, and focused our individual dreams through our commentary or assistance.

      My late business partner had a test: he would just start asking “But is it any good?” and keep on going, until we either had something to do, or floors could be spotted, and inadequate thought averted.

      Just about everything I do is meant to reflect the good memory of my friend who was a incredible expositor of the positive in life, and scourge of inadequate thoughts. The passion I hold for involvement did not solely originate with my late friend, but was nurtured by many years of guidance and intellectual generosity. I think everyone here who contributes or adds to the debate is in some way honoring their own positive influences in life. We’ve such a scope here to be a good influence, in turn, I’m desperate to see this turn out well. It’s part of my good dreams, and so let it roll.

      Go for more, not less, and I do not mean word count, for those of you who want to scroll by what I write!

      • Dear John ( other John ) and maybe other TJ readers, here’s a publication that I would highly recommend reading, and think you would thoughly enjoy, if you can find a copy. It’s called –

        Automobile Design : Great Designers and their work

        Edited by Ronald Barker & Anthony Harding
        Published in 1970 by David & Charles
        ISBN 0 7153 4905 8

        and covers the careers of

        The Bollees
        Fredrick Lanchester
        Henry M. Leyland
        Hans Ledwinka
        Marc Birkigt
        Ferdinand Porsche
        Harry Miller
        Vittorio Jano
        Gabriel Voisin ( my hero )
        Alec Issigonis
        Colin Chapman

        If you don’t recognise some of the names – just Google to see what geniuses these men were 🙂

        I have a 1st edition which as you can see has 11 designers – the 2nd edition has 12 ……



        • Just ordered the “last” copy.

          Taiichi Ohno: Toyota Production System

          is so far my favorite auto / engineering book.

          Pure poetry.

          But I’m really looking forward to reading Barker and Harding.

          I’m guessing you’re more widely read on auto subjects. Think we could drum up a book review every now and then? I’d have different angles, but no probs getting review copies, or making the time. Once a month maybe?

          Thanks, mankyboy, no better gift than a good read that can enlighten. ~ john

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