Let’s analyze how the floor of an F1 car works, one of the most crucial elements of a single-seater as it generates the majority of the aerodynamic load.
The 2022 regulations have emphasized the ground effect in Formula 1. The current generation of cars uses the underbody to generate most of the aerodynamic load, practically half of the total. It is, therefore, a fundamental component for the performance of a single-seater. For this reason, we want to examine how the bottom of an F1 car works specifically.
The physics of a Formula 1 floor
The operating principle of the floor is the Venturi effect. It is a phenomenon where fluid pressure decreases as its speed increases. The entire process is governed by the simplified Bernoulli equation for a steady, incompressible flow without changes in altitude:
P + 0.5*ρv2 = constant
where P is pressure, ρ is density, and V is velocity. It can be seen that as the speed increases, the pressure must decrease, and vice versa.
The bottom of an F1 car is designed to exploit this principle precisely. There are two channels known as Venturi channels. These have a wide entrance section to capture the airflow (A), narrow in the central part of the bottom (B), and then widen again in the diffuser area (C). This shape causes the airflow to accelerate, and thus, as seen before, generates a low-pressure zone. This creates a suction effect, downforce, which keeps the car glued to the asphalt, allowing it to carry much more speed through corners.
In the diffuser area, the channel expands, allowing pressure recovery. This facilitates the extraction of air towards the rear of the car. In the diffuser, the pressure increases again, but this ensures better maintenance of pressure conditions and flow beneath the car.
How the flows under the floor of an F1 car are managed
Now that we have seen the operating principle, we can analyze how teams manage the air under the car. The goal is to have the cleanest possible airflow for better performance. For this reason, not all the collected incoming air is sent into the main channel of the bottom.
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In the inlet sections, there are fences that direct the dirty air, coming from the wake of the wheels and suspension arms, outside the car. Additionally, these components also generate small vortices that help feed the main channel (blue). Some of the air is also channeled into the side area of the floor. However, this serves more to feed the rear ducts.
For teams, it is crucial to prevent external air infiltration under the car. Miniskirts are no longer allowed by the regulations, but teams try to recreate them pneumatically. To do this, it is essential to work well on the “curb” of the bottom, but the height from the ground also plays a significant role.
The importance of ground clearance
An F1 car functions much better the closer it is to the ground. This brings us back to the Venturi effect. The closer the central part of the bottom is to the ground, the more the air is forced to pass through a smaller section, increasing its speed. This generates an increasingly intense low-pressure zone, and the car is sucked down to the track with more force. Therefore, the generated load increases. Of course, there is a limit because if the air is too restricted, the flow “interrupts,” triggering the porpoising phenomenon.
Another important factor, where ground clearance plays a key role, is the pneumatic sealing of the car. Teams work extensively on the side of the bottom to find shapes capable of generating a vortex structure that prevents external air from infiltrating under the car. This structure is stronger the closer the curb is to the ground.
When the car is lifted, there is a double negative effect. The first is that the load generated by the bottom decreases. The second is that the lateral vortices weaken, making it easier for external air to infiltrate under the car. This can cause sudden loss of load and instability.
Teams are working hard to ensure the best possible working conditions for the bottom. The goal is to have a more consistent aerodynamic map. For example, Ferrari suffered a lot in this regard with the SF-23. The bottom is one of the most important components, and teams guard it closely. This year, thanks to the incidents in Monaco, we had the opportunity to observe some bottoms, allowing us to understand even better how the bottom of an F1 car works.