In modern Formula One there are only a few areas where designers have any aerodynamic freedom. The outer part of the front wing is one; the zone around the rear brake ducts and surrounding floor is another.
The regulations governing the location of aerodynamic parts around the rear wheels are complex and going listing each one will be a boring exercise, but it is worth running through the essence of what they say.
Article 3 of the FIA Technical Regulations governs bodywork dimension. Bodywork around the floor is permitted as long as it does not extend a certain height above the reference plane and meets certain (restrictive) cross-section area and curvature requirements. Furthermore the floor must form a solid structure – i.e., cannot contain holes, which was a particular area of dispute in 2012.
Article 11 describes the brake ducts. It defines a cube-shaped area within which aerodynamicists are free to have as much or as little bodywork as they like. The position of this area is 160mm above and below the wheel centre line, 120mm from the inner face of the wheel towards the car, and 330mm fore and aft of the rear wheel centreline. In this area we see a proliferation of carbon fibre which is clearly designed to enhance downforce rather than improve braking performance.
The first illustration below shows some the detail around the RB10:
First, note the detail around the brake ducts. In this configuration the duct opening is quite small and there are at least four winglets protruding from the ducts. The brake ducts contribute substantially to the downforce produced at the rear of the car. This downforce is generated very close to the rear wheel, which helps get heat into the tyres and reduce degradation.
In addition there a number of flicks and vanes attached to the floor of the car. These serve the purpose of manipulating the airflow around the rear wheels to optimise the wing-wheel interaction. The tyre creates a lot of drag — this can be reduced by diverting airflow either side of the rubber or by altering the flow the structure hitting the rubber.
Also note the slot in the floor. Although this looks like a hole there is a hairline gap from the edge of the floor to the slot so it complies with Article 3 in the Technical Regulations. Again, this slot is designed to bleed air below the floor to optimise the wing-wheel interaction. This slot can’t be too large or else it would create too much turbulence, which would increase drag.
The illustration below shows the brake ducts from a different perspective – again note the complexity of the device with brake cooling being a secondary objective!
The original intention of the regulations was to ensure teams could properly cool the brakes. This is a very important safety requirement as we have seen with some recent high profile brake failures. Canny F1 engineers have exploited the regulations for aerodynamic benefit.
But as with double diffusers, exhaust blown diffusers and other inadvertent aerodynamic loopholes, don’t be surprised if FIA decide to impose tighter control over brake duct design to reduce their aerodynamic benefit in the future.
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Images © John Beamer