The change in the 2014 Formula 1 rule book will bring about a shift in how teams manage the airflow around their chassis. The main cause for this shift in aerodynamics is the mandated repositioning of the exhaust exit to the center of the car, just between the diffuser and rear wing, which should not allow any more use of the exhaust gasses for aerodynamic benefit. The extradition of the exhaust from the floor of the car could lead to a change in aerodynamic effect to advert tire squirt, and may end up helping this new generation of Formula 1 cars look different than some initially anticipated.
An exhaust blown diffuser works by running the exhaust exit either below or above the diffuser/floor to increase the airflow underneath the diffuser. The faster the air flows at the rear of the floor, the more that the air is stretched thin, creating a lower pressure area and pulling the car down. An added benefit of these blown diffusers were the sealed off airflow around the diffuser that would otherwise be disrupted by the turbulent air running off the rotation of the tires.
The FIA's first attempt at 'banning' blown diffusers was only met with ingenuity by Formula 1 engineers through the utilization of the Coanda effect to reposition the exhaust gasses back down toward the diffuser and seal off the turbulence from the rotating tires. Infinity Red Bull Racing have been particularly noteworthy regarding the blowing of the rear diffuser, and their chief aerodynamicist, Adrian Newey, has been able to extract performance from the blown exhaust that no team in the paddock can seem to match.
In the 2014 Formula 1 rulebook, the exhaust has been repositioned by the FIA to a place where no engineer or aerodynamicist should be able to extract any extra performance; this means that sealing the rear diffuser from tire squirt has to be met with some other sort of innovation. Just a few years ago, the exhaust, up and down the grid, was in no place to aid the diffuser, and the cars were adorned with all sorts of winglets and vortex generators that helped to seal the diffuser and rear wing off from the tires, as well as create downforce on their own. In 2014 with the exhaust repositioned, the designers will have to find some other way to clean up the tire squirt and improve the efficiency of the diffuser, and may revert to some of those winglets and floor cuts near the rear of the floor.
The similarity of the 2014 F1 cars with the 2008 chassis may remain distant due to the 2009 bargeboard ban, even though the engineers would love to be able to control the air surrounding the rear of the car with a ridiculous amount of winglets and fins. However, the similarities of the 2014 chassis may be much closer to the 2009 cars, as Criag Scarborough explain's in a comment to his article, 2014 Rules: First Look:
scarbsf1on July 9, 2013 at 9:29 am said:
With no exhaust blowing the diffusers edge, the footplate area will need to be shaped as it was pre 2010 to offset tyre squirt, so lots of slots and coved tyre decks.
This will be an area of extreme interest to the 2014 designers who will try and skirt around the complicated old rules banning "extemporaneous bargeboards" from the rear body work in an attempt to control the turbulent air from the tires ruining the efficiency of the diffuser. Pair this with the changing engines/power systems, and we are looking at a season that could possibly be won with a bit of luck from a team that picks a cleaver innovation and runs with it while everyone else is trying to catch up on the new engines.