"Batman" is the name used in motorsport for the peculiar wings, triangular in shape, that most of the Formula 1 cars used, until 2008, placed ahead of the rear wheels.
The way it operates has little to do with a conventional wing and its base concept originated in the delta wings of supersonic fighter aircraft.
In the mid-eighties it began to be used on the side pods of the IndyCar, small aerodynamic devices in the form of inverted delta wings, whose aim was to take advantage of the free space left in the sidepods, narrowed in that area, to obtain some additional downforce.
This was the start of the single setter use of a concept of wing that was originally developed for supersonic aircraft and later used in the "space shuttle” that had, until then, limited application in racing cars.
The concept of delta wing had been, since the sixties, used discreetly, as small fins, called "dive plates", applied to the bodywork of the GT and Sport- Prototypes cars, in order to balance the downforce of these vehicles.
The delta wing, designated by its triangular shape, when used upside down and positioned in an angle of attack with respect to the air flowing over it, as can be seen in drawing 2a, will induce the formation of a vortex in the underside of the wing, which develops along its free edge (the other is attached to the bodywork) and moving along this edge in the entire length of the wing.
This vortex is created by the sudden inflection of the airflow to overcome the leading edge of the wing.
The vortex thus generated will be stronger the more sharp is the leading edge and the greater the angle of attack. The drag caused by such wings is smaller in the case of a delta wing with rounded leading edge, as used in the "space shuttle", but in these wings, the induced vortices have lower strength.
This vortex is being boosted, in its path along the underside of the wing, by the inflow of new air flows ranging flowing along the wing’s leading edge and that will feed the growing vortex.
The vortex airflow is rotating on itself at a very high speed. Since we know that the pressure in airflow is inversely proportional to its velocity, we can easily imagine that it will induce a negative lift force applied along the entire free edge of the lower face of this delta wing.
In the remaining area of the lower surface of the wing, limited externally by the vortex, the air flows smoothly and linearly, as if it were a conventional wing and, as can be seen in drawings 2a and b, inducing a negative lift of considerably less force than the one produced by the vortex.
In drawing 2b we can compare the negative aerodynamic load difference induced by these two types of flow on the lower surface of a delta wing and may also observe the gain in strength of the vortex, then of the force induced in the wing by the vortex, when the external delta wing edge is in additional angle with respect to the airflow.
When compared with a traditional wing, the delta wing is less effective, not only because it requires a greater angle of attack to achieve similar aerodynamic loads, but also because the drag produced for the induction load is higher than that of a conventional wing.
The great advantage of the delta wing is that of maintaining effective, with adherent airflow in the lower face, when working under turbulent airflows and at angles of attack higher than tolerated by a traditional wing, which loss would occur at an angle of attack in which the delta wings usually are more effective.
The drag produced by this type of wing is, as stated above, higher than by a conventional wing, but the fact that their effectiveness is due to the vortex created in it, allows it to remain effective when crossed by turbulent airflows.
The wide use of such wings on Formula 1 cars of a few years ago, when the technical regulation allowed the use of free space on the side pods, ahead of the rear wheels, is very telling of its effectiveness in achieving aerodynamic load.
But its widespread use did not prevent that every single setter presented a different wing, in a diversity that was derived from the fact that a technical device streamlined to suit a vehicle does not necessarily work well when applied in another vehicle.
Thus, comparing the three best cars of 2005 Formula 1 season, we found that while Renault (drawing 3) adopted, from the European season, a double delta wing, McLaren (drawing 6) and Ferrari (drawing 9) remained faithful to the single delta wing, with the Italian team, from mid-season, to add a small delta wing, placed at the beginning of the side pods, at the same height as the main delta wing.
In Renault that used two delta wings, the main upper and the lower secondary, their technicians managed it in order to get an additional downforce at the expense of a slight increase of drag.
In circuits where they needed bigger aerodynamic loads, the French team chose to use an upper wing with side fins, as we can see in drawing 3, which allowed generating some additional loads at the back of the wing, where it worked as a traditional wing, with separated upper and lower faces airflows.
When used in the delta wings "pure" configuration, as seen in rear and bottom view in drawing 5, the outer edges of the wings were in additional angle, inclined upwards, in order to increase the angle of attack of this edge of wings and to induce the formation of a strong vortex along it.
In McLaren, as can be seen in drawings 7 and 8 (in back and bottom view), the technical staff chose to keep the simplest wing, being perhaps the most effective of the three solutions presented here, which worked almost exclusively as delta wing.
Inferior and rear views (above) and lateral one (down) of McLaren MP4/15-Mercedes’s delta wing, with visualization of the streamlines of the air flowing over it.
In the rear third of the outer edge, also inclined upwards, in further angulations, a side fin extended only to the upper face, allowing the vortex created in the bottom side to continue to be powered by additional airflow but preventing that the airflow on the upper surface of the wing to pass to the bottom face, gaining here some additional aerodynamic loads.
In Ferrari (drawings 9 and 10), they used throughout all the season a mixed wing, where the front two-thirds functioned as a delta wing and the rear third as traditional wing, by the introduction of side fins. Although the vortex created in the front part of the wing is maintained on the back thereof, the use of side fins made the airflow a two-dimensional one, separating the upper and bottom wing airflows.
Article by António Eiras - 22/02/2015
From the middle of the season, the Italians single setters began to use a small fins placed at the front end of the side pods, as can be seen in the same figures. These wings operated together with the main delta wing as a strake, that is, its original function was to create a vortex that reaches the edge of attack of the main delta wing and would lead to be generated a stronger vortex than the one that would be created from a airflow which had not been disturbed in its path along the lateral surface of the side pod.
With the additional wing, the aerodynamic loads produced by the main wing will be greater, thus improving its effectiveness, similar to the effect achieved in fighter aircraft, by the strakes on the main delta wing.