In F1 one thing is clear: every team wants to design the fastest car on the grid. However, there is no general solution to the challenge of designing the 2022 sidepods. This has been very clear ever since the testing sessions in Spain and Bahrain. In this article, I am going to give an insight into the technical reasons behind the choices made by the top 3 teams in how they produced their sidepod design concepts. Changes will most certainly be made as the season progresses, as each circuit has its own characteristics and engineers begin to tweak the design and improve performance.
The overall purpose of the new sidepods
The 2022 technical regulations brought a new era to Formula 1 aerodynamics. The cars use the concept of ground effect in order to produce downforce which implies heavy aerodynamical changes to the body of the car. With the introduction of ground effect, the sidepods are now used for more than cooling purposes and their shape is no longer dictated by the need for drag reduction. However, the aerodynamical goals of the new sidepods are to increase downforce, decrease drag and work with the help of the floor towards sealing the underfloor (the floor is the side viewed from above and the underfloor is the bottom side). While the first two seem obvious, why is there a need to seal the underfloor? In order to understand this, let’s take a look at the concept of ground effect and the relation between the sidepods and the floor:
F1 ground effect is the phenomenon which occurs when the sidepods of the car are shaped like inverted wings which use the venturi effect to produce downforce: creating a low pressure area under the car produces downforce with the help of higher pressure which pushes the car down onto the track. As the car moves over the ground, the track can be imagined as the floor of a venturi duct. When running air through a duct, the same amount of air particles that enter the duct must also exit (qin = qout, q=airflow). However, if you restrict a small portion of the duct, the air particles will have to travel faster through this area called the throat due to the law of mass conservation. If Bernoulli’s principle is applied to this case, higher air velocity implies pressure loss: air particles create pressure through their random motion. In order for the air to speed up, a part of the kinetic energy from this random motion has to be transformed into the energy of the forward airflow. This leads to losses in air pressure, as the particles have less energy to shift randomly.
For this effect to work at its peak, the floor needs to be sealed, which is achieved through a variety of engineering solutions. First, the floor is very close to the ground, which means that the cars are set up with very low ride heights. Second, the edge of the floor has cuts, curls and ripples which build and release vortices used for sealing the underfloor (the ripples create vortices, the curls shape them and the cuts release them).
Why is sealing the underfloor so significant for ground effect? Through an underfloor seal, the leak path of the airflow is blocked, so the low pressure under the floor is kept the same, leading to no aerodynamical losses. Technology from the previous ground effect era used sliding side skirts to engineer around the same problem, but they were soon banned due to safety issues.
The design spectrum
There are 3 significant categories of sidepod proportions: Ferrari, Aston Martin, Alfa Romeo and Haas went wide, Mercedes and Williams went narrow and the rest went with an in-between size. Later this season, Aston Martin changed their design concept to a medium size sidepod. Each type has a slightly different philosophy in terms of how the sidepods interact with the airflow around them, however, the main objective for most of the teams is to tidy up the heavy airflow towards the back of the coke bottle area of the cars, where it comes in contact with the airflow through the diffuser. Other important targets are increasing floor performance and managing front tyre wake.
The wide concept: Ferrari
Ferarri is one of the teams with the most striking sidepod designs in the paddock. The sidepods are very wide, as the team has opted for a long and narrow body, but horizontal radiator inlets and they maintain the same approximate width all the way towards the back, where they eventually narrow. The cooling inlets begin with a straight line, from where they curve towards the back, creating a wing effect. This reduces drag, as their shape is very aerodynamical.
The front of the sidepods have an undercut which replicates the shape of the floor more aggressively, channelling the airflow to create downwash. This feature is extremely important for achieving the goals of the sidepod design. If we apply Newton’s third law stating that every action has an equal and opposite reaction, the action of downwash created by the undercut corresponds to the reaction of positive pressure air. This occurs right under the inlets, which produce a series of consequences: the air separation from the floor is reduced, tyre wake is outwashed and the air that flows towards the floor is more energised, creating more powerful vortices which seal the floor more efficiently. Another significant consequence is the increased downforce generated through better suction at the front of the underfloor which is achieved with the help of the high pressured air under the cooling inlets.
After the curvature of the cooling inlets, the sidepod is designed to be straight in order to maintain the outwashed front tyre wake at a distance, so it then clashes with the rear tyre instead of attaching to the body of the car which would disturb the airflow going towards the coke bottle area. At the back, the sidepod narrows in order to achieve this coke bottle shape. The importance of the coke bottle shape is mainly given by its effects on downforce production due to its relation to the diffuser, which is similar to the relation between the beam wing and the diffuser. This shape also facilitates the airflow around the rear tyres, managing some rear tyre wake and airflow towards the rear brake ducts.
In order to maximise the effectiveness of the airflow going on top of the overbody, the top part of the Ferrari sidepod channels the air to the beam wing through its pool-like design. The beam wing is incredibly important for producing downforce and increasing the performance of the diffuser. The beam wing creates downforce on its own, which means that positive pressure is at the top of the wing and negative pressure is at the bottom. Knowing that the beam wing sits above the diffuser, the negative pressure (also known as low pressure) is located at the top of the trailing edge of the diffuser. In contrast, the air pressure which reaches the rear of the diffuser is high. The difference in pressure between the two sides of the diffuser creates the phenomenon which benefits the suction of airflow through the diffuser. This happens because the energy levels of the airstreams want to balance each other out, so high-pressure air tries to spill over to the low-pressure side.
Picture from: www.wikimediacommons.com
The narrow concept: Mercedes
The most shocking side pod design this year is the work of Mercedes, a design which is called “size zero’’. This is the most radical take on the regulations, with the 3 main objectives being drag reduction, floor performance and efficient cooling.
The sidepods have a tall and narrow radiator inlet and widen out further down towards the floor, creating a downwash effect. This directs the air (which travels around the sidepods) towards the floor. Width is the main factor in terms of the design of the Mercedes sidepods: they look very taken in from the profile view of the car, however, viewed from above, the true size of the sidepods is more reasonable. This is done for the purpose of reducing drag, as bulkier surfaces tend to generate more drag. The result is that the interaction of the sidepods with the airflow around them is minimised, however, this doesn’t mean that the sidepod shape doesn’t direct the airflow towards specific points of other parts of the car.
Through the side crash structure, which is exposed and designed to be aerodynamic and turning vein-like, some of the airflow is directed towards the top part of the sidepods in form of a powerful vortex travelling from front to rear which also creates downwash. The downwash effect of the sidepods leads the airflow towards the floor and towards the coke bottle area. With the help of the leading edge of the floor being raised and exposing the front of the turning vanes mounted inwards on the underfloor, outwash is being created along the bottom side of the sidepods, thus sealing the floor all the way towards the back.
Picture from: foxsports.com.au
The in-between size: Red Bull
Red Bull have also turned heads with their sidepods, designing some very aggressive ones and sharing the concept with Alpha Tauri. The aggressiveness is true in the case of the radiator inlet, however, the general shape of the sidepods follows the same concept and goals as some other teams on the grid. Red Bull is using the same downwash technique in order to pressurize air near the radiator inlets (same technique used by Ferrari and Mercedes), but the upper side of the radiator inlet shell is cut back. This is due to having flexibility with rearranging the lower leading edge of the radiator inlet for specific aerodynamical and cooling demands. It also leaves space for aerodynamic development, which a normal upper leading edge would not allow as easily. The Red Bull engineers have found a very clever way of fine-tuning their cars for specific needs in terms of aerodynamics. Also, the top of the sidepods create downwash towards the gap between the rear wheels, something Alpine and Alpha Tauri have also incorporated into their design.
Picture from: Motorsport.com
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