to a fast car is to get the air from the front to the back as smoothly and quickly as possible , while making maximum use of its grip-inducing properties along the way .
Imagine an aeroplane wing : its underside is flat , the upper surface curved . Thus air going over the top has to accelerate to keep up , and when it does its pressure drops . There ’ s more pressure beneath it than above , so you get lift . Turn the wing upside down and put it on a race car , and that generates negative lift , or downforce .
Now flow the air beneath a car where the underside of the chassis is aerodynamically shaped , with an intake at the front , a level section , and then an upcurving diffuser to exhaust it all , and what happens is what Swiss boffin Daniel Bernoulli discovered in the 18th century , long before anyone knew what a car was . Run the airflow through that restriction betwixt chassis and ground – he called it a venturi – and its flow is speeded up and its pressure drops . Hey presto , there ’ s your undercar downforce or ground effect , pulling the whole car down to the track surface and doing it with less drag than you get using wings .
What Mercedes cleverly spotted was that the way the rules were framed you didn ’ t have to cover side impact structures with the usual sidepods with their downwash aerodynamics which were intended to smoothly direct the important airflow down the sides of the chassis and through the crucial gap betwixt the powertrain and the rear wheels . They postulated that a ‘ zero ’ sidepod design would facilitate much greater airflow down the sides and through that gap .
Just like the lengthened undercar aero devices on the aforementioned Lotus 80 , this different but equally clever idea promised vast downforce , so not surprisingly the team chased it . More downforce = more grip = more speed = more wins = more championships .
It might not quite be rocket science , but it ’ s just as complex . Because there was always a problem with too much downforce , even in the first ground-effect era . And that was called porpoising .
Basically , to generate decent downforce the chassis and floor must be incredibly stiff to withstand the forces generated . That means you want the suspension as stiff as you can get it without making the handling too spooky and harsh , because you want the basic car platform to absorb all the loads and stay as level and stable as possible . But forward motion at high speed is not just about aerodynamics , it ’ s about mechanical effects , too .
What happens beneath the car is this : the faster it goes the more the air beneath it speeds up and the greater the undercar downforce that is generated . But that can increase to the point where the flow becomes so great it pulls the chassis ever closer to the road until the venturi stalls , whereupon the ride height increases again . That reduces the stall and the process begins again but when that oscillation is happening very quickly at very high speeds it induces a violent up and down heaving motion in the car , and that ’ s porpoising . Allied to very stiff suspension to maintain that level platform , it can be incredibly uncomfortable for the driver . In the previous year ’ s flat-bottomed W12 , the aerodynamics would have damped out such oscillations , but with the mechanical side of things the 2022 aero also induced a mechanical vertical bouncing , which made things even more uncomfortable .
And this is what Mercedes spent all of 2022 chasing , trying to understand why their car refused to behave as predicted . Some of the problem lay within the accuracy of their simulation tools which failed to produce accurate predictions ,
↓ James Allison , Toto , Jérôme d ’ Ambrosio and Bradley Lord , Canada , 2022