F1 BODY & DIFFUSER
You may have heard the term BARGEBOARDS before when pundits talk about F1 cars. They are effectively carefully shaped panels behind the front wheels and in front of the side-pods.
The main purpose of them is to shape and deflect the airflow to different parts of the car. The y-250 vortex is created by the front wing and helps keep the airflow smooth along the body. the bargeboards coaches the vortex around the body of the car and allows clean air to pass through the air intake.
The bargeboards themselves and also the turning vanes (elements situated further up the nose) are also shaped to create their own vortices around the car floor which seals in the fast, low pressure air under the body. This stops it from leaking out which would reduce the downforce massively.
Pictures showing the bargeboards on a simple diagram. Where the bargeboards are in red an turning vanes in orange
Ferrari SF90 to the left showing its bargeboards. Note all the intricate fins and panels trying to make the car as aero efficient as possible.
DIFFUSER & GROUND EFFECT
The word DIFFUSER is also thrown around a lot when talking about Formula 1 cars. That is because they play a very important part in creating downforce for an F1 car. The diffuser is the section of under the car that transitions the air from under the floor to the outside air outside the car.
Something counterintuitive is that the floor/diffuser produces a lot more of the total downforce of the car than people think. To an average person, they probably would think that the front and rear wings produce the majority of the downforce as they are easily visible and the floor is, well, just a floor. However the floor/diffuser produces just as much and sometimes more than the wings of the car because of something called ground effect.
Ground effect was pioneered in the mid-1960s when aerodynamicists attempted to find more downforce without increasing drag like you get with wings.
It works the same way as wings. The car floor is situated very close to the ground. The smaller volume of space increases the speed of the airflow in this gap due to the Venturi Effect (explained on Aero Homepage). This creates an area of low pressure which the car is sucked into; giving a lot of downforce.
In the late 70s and early 80s Lotus were exploiting ground effect massively resulting is very high cornering speeds. They fitted skirts to the side of the cars to prevent the low pressure air under the car from escaping out the sides which would reduce downforce. See the yellow on the diagram of the Lotus '79
However, this presented a huge safety concern for the FIA as if the skirt was damaged or broke mid corner, the car could suddenly lose a large amount of downforce and skid. Also if the floor touches the ground then the airflow will stop altogether losing basically all ground effect. To stop this, ground effect was effectively 'banned' as cars had to have higher, flat floors (with the exception of the diffuser) and skirts were banned. All modern F1 cars have a plank floor reference plane and also a stepped plane on either side that is a bit raised.
But. Ground effect is back for the new 2022 regulations. Why? Because F1 cars nowadays are a lot safer and all the complicated over-body aerodynamic development has created so much turbulent air behind the car (dirty air) that following cars find it hard to overtake or even keep up.
To see how this has changed visit the page here: 2022 Regulations
Going back to what a modern diffuser does is that its main purpose is to provide space for the transition of the low pressure air to the ambient outside air behind the car. It expands the air out gradually making the car more aerodynamically efficient as if it was a sudden transition the low pressure air would not be able to exit the car at the back as the high pressure air would be blocking it in. This would result in a higher drag penalty. A diffuser also haas vertical straights (see pink on picture) which guide the air smoothly out the back of the car reducing turbulence.
See the simulation showing the speed of the airflow decreasing as it passes through the diffuser. (yellow high speed, blue low speed).
There was controversy in 2009 when the newly entered Brawn GP car sported a revolutionary 'double diffuser'. This means that the diffuser has two layers (see picture) and therefore has a greater volume than single layer designs. Both Williams and Toyota also has double diffusers and benefited hugely because of it. See the picture showing the difference between single and double diffusers. F1 banned double diffusers for 2011 and Red Bull predicted that the loss would cost 2 seconds a lap at some circuits.