Blowing the air across the wing plane reduces the boundary layer which in combination with the steep angle of attack of the wing creates more downforce. At a certain threshold the blowholes reach a point where they can't produce enough air to stop the wing from stalling and so drag is reduced. Careful management of the wing AoA and the size of the pylon blow holes will decide the speed threshold at which the wing loses downforce and drag.
Lotus placed their exhausts in a more aerodynamically neutral position than say McLaren this season and as such have a more consistent aerodynamic platform. Realising that without EBD the downforce level is inconsistent the team have decided to achieve downforce in a more consistent way via the Rear Wing (Including the Beam Wing) and airflow en mass over the Diffuser.
The addition of the pylon for the passive F Duct required the team to have the engine cover finish further back toward the wing and so a funnel now presents itself at the Monkey Seat / Beam Wing. This Funnel and Monkey Seat act together acting as a mini diffuser atop of the beam wing creating more downforce.
Something to think about?....
Before the FIA increased deflection tests and then latterly mandated the size of the slot gap teams intentionally designed the top flap to flex under load closing the gap between it and the main plane. This had the desired effect of stalling the wing and reducing downforce/drag as the AoA of both wings combined became too large.
As a parting thought on this subject I propose the use of a trailing edge Gurney that although dimensionally would be within the regulations (The Latter part of article 3.10.1: Once this section is defined, ‘gurney’ type trim tabs may be fitted to the trailing edge. When measured in any longitudinal cross section no dimension of any such trim tab may exceed 20mm.) would be different to the perceived Rear Wing 'Gurney'
If we take the current design of the Red Bull, Ferrari & McLaren diffuser gurneys as inspiration these Gurneys act as a method of increasing downforce through airflow injection. Using a similar design approach at the trailing edge of the rear wing flap could produce more downforce . Similarly it could be used in conjunction with the flap to stall the main plane by the use of flex. The Gurney doesn't have the same deflection tests as the flap and main plane and so could be designed so that the gap is open to generate downforce and closes at higher speeds. The 'Gurney' has no real restrictions placed on it's design and so could have a small or large chord as long as it doesn't extend beyond the 20mm mandated. The height of the gurney and the slot gap left between it and the flap could be adjusted in order to suit the characteristics of the downforce/drag reduction required.
As usual these are my thoughts and should be taken with a pinch of salt as I haven't got access to CFD etc in order to access the general principles and most importantly the effects of DRS when the top flap is open may make the idea mute. In my eyes the Gurney could offer a source of both additional downforce and drag reduction by lending principles from former designs.
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