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TECHNOLOGY – BLOWN FLOORS


A load of hot air?


Formula 1’s blown diffuser theory was topical in 2011. While designers are still trying to master it in 2012, one student applied the theory to a Pilbeam Sportscar


I


n 2010 and 2011 there was one major area of discussion surrounding Formula 1 aerodynamics. With the banning of the


multi-level diffusers pioneered by Brawn, Toyota and Williams, Red Bull had found a new way to boost the performance of its car’s underbody – it had placed its exhaust exits lower than was then conventional, so the gas from the pipes blew into an area around the rear wheels. Using exhaust gases for


aerodynamic gain was not new. Various Formula 1 cars over the years have featured ‘exhaust- driven diffusers’, many of them designed by Adrian Newey, notable as the designer of the current breed of Red Bulls. Key to this is using the gases expelled by the exhausts to energise the flow around critical components


BY SAM COLLINS


such as wing elements or, more importantly, the diffuser. The concept is not only limited


to open wheelers and has also made an appearance in Sportscar racing, with the Allard J2X of 1992. While that car is largely forgotten, it housed its exhaust tailpipes in a through-car tunnel, in theory increasing downforce. The concept had dropped out of fashion of late, possibly because the tools required to fully understand what is going on with the airflow were not well developed. Even then, it was the preserve of high-end cars such as the highly advanced Allard.


HOLLAND CALLING It was a subject that fascinated Dutch graduate, Thijs van Rees, who was working on a Phd at Cranfield University. He decided to make the concept the subject of his thesis, but not on the traditional top-end open wheeler. Instead, he picked out a mid-range, full-bodied car as the model for his study.


‘I used the Pilbeam MP98 CN


regulations Sportscar [shown in lead pic, above]. It was developed purely in CFD and later tested on track, which is fairly unique in that category,’ explains the Dutchman, who now works in Formula 1 with Williams. ‘The regulations for that class of car


“Using exhaust gases for aerodynamic gain was not new”


stipulate that exhausts must be mounted in a specific area and must point either rearward or sideways, which gave me an interesting challenge. But they do not prevent you locating them in an area that can bring aerodynamic gains.’ To study the implementation


of such a layout on a mid-range car (turnkey CN machines retail for around £80,000-£100,000 ($125,575-$157,000) makes this an unusual piece of work, and the results of the research are substantial. Van Rees was heavily influenced by Red Bull’s recent designs, which appear to be all about the flow structure around the rear wheel. ‘Their concept was to manage the wheel wake at the rear of the car, and that was to improve the flow through the diffuser,’ he explains. ‘Tyres are


July 2012 • www.racecar-engineering.com 67


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