Red Bull RB7 – Sidepods and Cooling

When the Red Bull RB7 was rolled out, it was clear the car was a neat development of the RB6, but was not an innovative car. As with well developed cars like this, its details are well thought through, a particular case is the sidepod design. If you look at the RB7s sidepods, from the radiators back they appear to slope away to nothing. This leaves the distinctive flat floor and open area ahead of the rear wheels. This creates an obvious aero gain, but how is cooling achieved with such a tight design?

Firstly the sidepod forms the main blockage to the rear wing and diffuser. We’ve seen several approaches this year to manage the airflow around the sidepods to the rear of the car. In each case the team are trying to get the best and most direct airflow to the top of the diffuser and beam wing. As the better flow these devices receive, the more downforce they produce and the less drag is required from a larger rear wing.

Since the 2009 aero rules sidepods are extremely limited in the openings they are allowed, so most of the flow has to exit between the rear wheels. Normally sidepods send the heated air from the radiators back through the tapered rear (known as the coke bottle, due to its shape). In a simple sidepod this means the coke bottle ends with an opening and the hot air passes out and over the diffuser. However this makes the tail of the coke bottle unduly wide, which creates a blockage between the rear wheels and blocks flow over the diffuser. Red Bull discovered with the RB5 that the radiator airflow can pass up towards the centre of the car and exit above the gearbox in a bulged opening. This keeps the tail of the coke bottle nice and narrow.

With the RB7 Red Bull have taken this a step further, there is no appreciable exits in the tail of the coke bottle, so nearly all the radiator airflow ends up passing through the bulged outlet. This means the coke bottle is the slimmest and simplest of all the cars on the grid. Clearly the huge floor area and exposed beam wing show how easily airflow can reach the rear of the car. The concession Red Bull has to make for this benefit is the increased blockage in front of the rear wing. But as they are aiming for downforce from the more efficient diffuser and beam wing, the rear wings effectiveness is not such a concern. Other teams have similar low swept coke bottle shapes, but each of them still exploits some cooling exit at the back of the sidepod. Given enough testing a fully enclosed sidepod with the central bulged outlet could be copied.

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