Technical analysis of the diffuser

Now, I believe you all have heard of diffuser and know what it is and where it is located, but how many of you actually know how the diffuser works?

The diffuser is responsible for creating the majority of the car’s downforce and is located towards the rear of the car’s floor as it slopes upwards.

Written by Ive Bauk, Edited by Aiden Hover

This ‘professionally’ drawn picture represents the simplified side profile of an F1 car’s floor. The green area shows low pressure air. The orange part shows the start of the diffusers effect. As the floor slopes up, there is more volume for the air to fill and so it begins to accelerate in order to fill the widening gap. Therefore, the diffuser is speeding up the air, sucking the air under the floor as it reduces air pressure. Lastly, the red area represents the end of the floor at which point the air matches the pressure under the rear wing and is almost ambient, reducing drag.

In summary, the diffuser sucks air from under the car and pushes it out the other side at a higher speed. It’s not as simple as that, however, as this process not only creates downforce, but drag. This is where teams get creative in order to reduce the drag. The main objective is to smooth the air flow around the car, but each team has two very big obstacles in achieving this. The rear tyres create lots of large vortices due to their smooth curved shape which destroy the gentle air. Teams attempt to seal air affected by the diffuser from the tyres, some examples of this are the double diffuser and the blown diffuser. The double diffuser was the invention which helped win Brawn GP their championship in 2009 as Honda designers found a loophole in the FIA’s new rule set which aimed to reduce aero. They were able to section the diffuser allowing the bottom part to be affected by the dirty air from the tyres whilst the top section reamined safe and secure. The FIA subsequently banned this technique for 2010.

Brawn GP’s 2009 car

To get around this, RedBull implemented their blown diffuser. In this case, the team would get around the issue by directing the exhaust gases towards specially designed slots within the floor which would seal the diffuser and split the air into two parts of flow. This was quickly copied by Ferrari and McLaren, as was the case with Brawn GP in 2009.

RedBull’s 2010 car

Moving into more recent seasons, teams attempted to clean the flow of air around the diffuser with highly complicated wings and flaps all around the floor. This worked, but would create much more dirty air for the car behind which would severely hamper the effectiveness of the following car’s aerodynamics. The FIA have reduced the team’s freedom with this area for 2021 in an attempt to fix this, but McLaren seems to have found a way around this. Click here to find out more.

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