Banned: How F1 finally overcame blown floor trickery

In the lead-up to the 2012 season, the governing body had made numerous changes to fight against the growing trend of using the exhaust to affect the car's aerodynamic output.

This had followed the ban on double diffusers, which had subsequently been enhanced in their second year by the use of exhaust blowing solutions which the FIA also made an attempt at stopping.

As we explained last week, the clampdown wasn't effective and in fact the tighter restrictions actually led to the practice mushrooming. But, with particularly stringent dimensional criteria being put in place for 2012, it was hoped the sport could move on.

However, with blown floors being such a good avenue for increasing car performance, designers were not going to sit back and let any opportunity pass them by.

The 'Coanda' effect

McLaren MP4-27 'Semi-Coanda' exhaust solution

Photo by: Giorgio Piola

McLaren introduced a solution that was most widely adopted for 2012, utilizing the exhaust plume to leverage the 'Coanda effect,' This was where the jet of exhaust gas expelled from the engine pulled nearby airflow towards it, and together would alter the overall trajectory of the exhaust's energetic flow regime.

This would result in it being driven toward the gap between the tyre's sidewall and the diffuser's outer wall, just as it was with the exhaust blown diffuser solutions used in 2011.

The critical thinking behind the design of the McLaren solution was that with the exhaust mounted in a pod that overhung the sidepod, airflow would still flow around the sidepod and into the coke bottle region.

Sauber C31 'Coanda' exhaust ramp

Photo by: Giorgio Piola

This was a key issue that the users of a ramp down solution, such as Sauber shown here, had to wrestle with. For the exhaust plume would mix with the flow ordinarily destined for the coke bottle region - diluting the effect of both.

Adrian Newey was having none of this though. He'd already convinced himself that the McLaren style solution was inelegant and that the full ramp configuration was not going to cut it either. He needed that coke bottle flow to remain uninterrupted, and so set about finding a way to reclaim it.

Red Bull's search for a solution that would offer the best of both worlds was much more complex and would utilise a crossover tunnel. This would not come without its complications though, as the team grappled with trying to make it work in the real world after simulations offered some promising potential.

So convinced was Red Bull that it was onto something special, it actually ran a benign exhaust solution through the course of pre-season testing in an effort to delay anyone being able to copy its arrangement.

It finally unveiled its crossover ramp solution on the penultimate day of testing, and duly came up against issues, as it suddenly found it had flow instability with the tunnel that made the car inconsistent on turn-in. But an almost unwavering belief that it was the right way to go rather than McLaren's idea led to an intense development phase for Red Bull.

The regulatory changes for 2012 not only had an impact on the position of the exhaust but also the surrounding bodywork. As such, many of the designs seen up and down the grid that used this Coanda-style solution had bodywork with a trough-like appearance. Dimensionally this was bounded by the new regulations and most opted for a simple letterbox style trough. However, Red Bull pursued numerous ways of manipulating this shape to influence the trajectory of the exhaust plume and tried different solutions, some of which hoped to manipulate flow into the tunnel beneath.

For the Chinese GP, Sebastian Vettel even reverted to the pre-season testing solution, as he not only felt it might arrest some of the issues he was having with the car but also help the team understand where those issues might lie.

A hole in this position, rather than a slot, was more aerodynamically potent, so the other teams believed its use by Red Bull was a deliberate infringement on the technical regulations. You'll also note at this point that Red Bull had changed the point at which airflow from the crossover tunnel had been moved (see right inset for initial exit), with flow now exiting further down the car.

The tinkering continued, now with a renewed effort being made to reshape the crossover tunnel's entrance in order to smooth the passage of airflow into the tunnel and beyond. This meant a total redesign of the sidepod, including the movement of the exhaust tailpipe. There was also a lengthening of the tunnel, the shape of the tunnel's entrance being enlarged and a vertical separating slot mounted within.

At this point it appeared that the team had finally got on top of its aerodynamic instability issues and the car behaved more predictably, meaning it could now hunt for extra performance. This would come from a continued push to refine the crossover tunnels and bodywork that surrounded the exhaust's shape and a renewed effort by Renault to find ways to stabilise the exhaust flow. You'll note that the shape of the sidepod bodywork around the exhaust would change from trying to influence flow into the tunnel to a section that protected the two flow regimes from one another.

Meanwhile, the team had worked out that the plume created by the exhaust's shape, itself mandated by the new regulations, was having a detrimental effect. In order to soften a damaging vortex that was being formed, it worked on using a Helmholtz resonance chamber. The amount of work done by Red Bull during 2012 to make its solutions work was monumental but that's not to say others on the grid were resting on their laurels either.

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Sauber, which did not have the luxury of being able to bring new parts to every race and had started with the ramped solution, would have a brief dalliance with the crossover solution before realizing the amount of development that would be needed to make It work. As such, it switched to a McLaren-esque Coanda solution during the season instead..

Ferrari F2012 different 'Acer duct' exhaust configurations used

Photo by: Giorgio Piola

Ferrari remained an outlier throughout, preferring to try and modify its 'Acer' duct solution on an ad-hoc basis while it worked out the best way to maximize the Coanda solution that it finally introduced.

The FIA let the use of these Coanda style exhausts slide for 2013 knowing the financial burden that teams had gone through to develop them. It was acutely aware that with the new hybrid rules coming into play for 2014, the ability to blow the diffuser with the exhaust would no longer be viable.

So, whilst it was never specifically banned by a target new rule, the regulations were altered to account for it. With the exhaust having to exit along the car's centerline going forward the days of blown floors were over.