In the latter part of testing at Jerez the Ferrari F138 appeared with a slot under the nose cone. In adopting a nose slot, Ferrari have followed other teams’ recent developments in this area. Contrary to much rumouring the slot is a relatively simple aerodynamic solution to improve the air flow under the raised section of chassis.
Nose box aero issues
The nose and the raised section of chassis it attaches to creates several issues for the aerodynamicists. Firstly the nose box forms a blockage in between the front wheels and reduces the flow that can pass in the gap between the wheels. Secondly the very high nose\bulkhead designs that are almost universal this year create a high pressure region under the nose\chassis that is effectively creating lift, thus working against the downforce.
Lastly the nose and chassis present some of the longest flattest sections of bodywork on the car (floor excepted) and thus a boundary layer builds up along these surfaces and can create issues with separating flow. A boundary layer is the airflow that is effectively stuck to the car; whereas the main flow is passing over the car. As the bodywork surface continues more airflow sticks and the boundary gets thicker. As the boundary later is not moving (relative to the car) it is providing no aerodynamic benefit and simply causes flow separation and aero issues downstream. It appears the nose slot is a solution to resolve these issues, which one of these creates the greater problem for the cars performance, is debatable, but a small aero gain can be had by easing this issues.
As long as two seasons ago, Red Bull also exploited a slot under their nose, its design was more discrete and even when the letter box slot at the top of their nose last year was introduced, the under nose slot largely went unnoticed. Thus the RB7 had a slot created at the intersection between the chassis and nose box. Rather than a slot being formed in the nose box shape, the slot was formed by a layer of bodywork being added below the chassis. The small duct formed by this panel lead back to the front axle line, where it entered a small recess moulded inside the monocoque. This recess was about the size of large paperback book and sported exit vents into the footwell area of the monocoque. I suspect this area housed the FIA timing transponder, but probably not much else, due to its small size. The cooling effect was probably of some benefit, although other teams do not see the need for specifically cooling the transponder.
In fact the benefit of the slot was the effect on the cars external airflow. As air passes under the nose, pressure and a boundary layer would start to build up. The airflow would then be split by the slot\duct airflow adjacent to the noses surface, air would enter the duct, skimming off the boundary layer in the, process. As the duct is also divergent it would reduce the air pressure under the nose at its entry, by the high pressure region venting into the slot. The off body airflow, that is the moving stream of air a few millimetres away from the bodywork and thus clear of the boundary layer, would pass over the slot and the reattach to the under surface of the raised chassis. This flow is moving faster and is at a lower pressure than the flow closely attached to the nose cone. Thus this flow will have more energy to work on aero devices downstream. By splitting the boundary layer and off-body flows at the slot, the preceding nose cone can be shallower, thus reducing the blockage it creates between the front wheels. This simple slot effectively negates the three negative aero effects presented by the nose box.
Ferrari solution is very similar to Red Bulls slot, but the slot is formed in the nose box itself. Legally the slot might be far forward enough to be considered the driver cooling slot, if so it will be restricted in inlet size. Or if the slot is behind the FIA defined A-A bulkhead line, then it will not be considered part of the nose box and has total freedom on inlet size.
The slot is mated to a corresponding opening in the monocoque, this appears to feed into the footwell area, I doubt that its purpose is to be ducted for aero effect elsewhere on the car (i.e. DRS) or cool anything that isn’t already inside the cockpit (i.e. KERS). The air most likely cools the driver from the ambient heat and the heat created by the power steering rack and electronics boxes.
This is a simple and effective solution, as the front bulkhead on the monocoque needs the slot made into it; it’s not something that can be easily copied in 2013.