EDIT 04/01/16 - Before you get your teeth into this article I can now verify I've seen a Technical Directive issued by Charlie Whiting that rules out the concept. (Although it's still worth a read as it not only explains my thoughts behind this concept but also the previous use of DRD and the F-Duct)
It's about that time when changes to the regulations cause us to have a good old look at what might now be possible. The implementation of wastegate exhausts has got us all wondering what advantage the teams can possibly glean. Unfortunately their positioning along the cars centreline rules out any edge of floor/diffuser blowing tomfoolery. However, how they're used along the centreline could yield some interesting applications in any case
Before we get going, make sure you're sitting comfortably and have a drink as this is going to be a long one. Let's start with a little history lesson.... (If you want to cut to the chase and/or don't need the history lesson skip to the end of the article where I've added a brief version of the Active-DRD concept)
|McLaren's blown rear wing concept was known in-house as the RW80 but when the media noted the chassis duct had the 'F' from Vodafone emblazoned on it, it became known as the F-Duct.|
|The shark fin engine cover connected the pipework to the upper flap|
|The flaps were hollow, allowing the airflow ducted to them to pass air through slots on their rear face|
|The slots on the rear face of the wing were placed differently depending on how the team wanted the wing to 'stall'|
|The Lotus drag reduction device seen implemented on the E20 here with flo-viz applied. You'll note the flow separation in the centre of the wing caused by airflow being blown laterally out of the slots in the pylon|
The base principle of the Lotus DRD is retained for my model, however, instead of requiring a blockage of airflow in the main pipework to cause the switching effect the wastegate is used to entrain the airflow into the lower outlet.
When drag reduction isn't required / inactive (ie the driver is cornering or braking the wastegate is opened), the plume it generates from the tip entrains the airflow of the pipework that surrounds it (see below) pulling the airflow through the sleeve. As speed builds and drag reduction is required the wastegate is closed and as it is easier for the airflow to pass over the lower, smaller diameter duct it passes up through the pylon to the underside of the rear wing and ejected into the rear wings path, this creates seperation, reducing downforce and drag.
Sounds like a slam dunk then, yea?
No, there are so many other factors involved in making this work. Firstly, the control of the wastegate(s): Having two wastegate exhausts does make things easier as it means you can isolate which one does low speed events (needed for this Active-DRD to work) whilst another takes care of any high speed usage. As I've already mentioned the MGU-H can fulfill some of the holes in terms of turbo management this creates, however, based on the way the hybrid systems operate it is plausible that not all manufacturers would be able to do this and/or it could have a performance effect on the powerunit, negating the aero gains.
Furthermore, there are other aero implications. With the loss of the beam wing for 2014 the teams have been using the exhaust to energise the aerodynamic structures that surround it, such as the diffuser and rear wing. Introducing two new energetic exhaust plumes into these structures will need careful management, as they will change the point of seperation. Throwing Active-DRD into the mix may further complicate matters but could also yield an increase in downforce not only a drag reduction boost.
How can you get more downforce? Teams run the rear wing (and other components for that matter) at an optimum level based upon how much downforce they can get before it compromises them in terms of drag (efficiency). That's why if you take the two extremes of Monaco (low speed street circuit) and compare it with Monza (essentially lots of straights punctuated by chicanes) you'll see a huge disparity in the wing angle being run.
With that trade-off in mind you'll note that sometimes teams essentially have to give up downforce based on the circuit and how others around them are performing. But, what if you could have your cake and eat it? That's what happened in 2010 when the F-Duct was the must have aero appendage. Teams had already designed their challengers around the double decked diffusers that had caused a ruckus in 2009 and were in the throws of another war: exhaust blown diffusers (EBD). Meanwhile, McLaren's RW80/F-Duct meant that teams not only focused on downforce but a way of reducing it and drag with it. The rear wing assemblies used during 2010 were positively barn doors in comparison to what the teams use today.
Another spanner in the works for 2016...
Just to make things more interesting the rules pertaining to the mainplane and flap geometry have also been amended in the latest draft of the regulations, making the use of a 'Spoon' rear wing more achievable. For those unfamiliar with the 'Spoon' design it can achieve more downforce from the central portion of the wing as it dips below the mainplanes intended legality window, whilst the outer sections being shallower help to retain a smaller drag footprint, meaning the car punches a different wake profile.
|Sauber C32 in Australia 2013 with a 'Spoon' style rear wing|
When the new regulations were introduced in 2014 they increased the previous Y75 zone to a Y100, inline with the exhaust placement regulations. This allowed the winglets (Monkey Seats) to be increased in size too, whilst some teams opted to run dual mounting pylons 100mm from the centre line too, with the Mercedes W05 probably being the prime example, although Sauber have continued the trend this season.
What the regulations didn't do was adjust the centreline measurement for the mainplane and top flap, even though it had been proposed, in order to mitigate some of the downforce that had been lost. This changes in the new regulations though:
3.10.8 Any horizontal section between 600mm and 750mm above the reference plane, taken through bodywork located rearward of a point lying 50mm forward of the rear wheel centre line and less than 100mm from the car centre line, may contain no more than two closed symmetrical sections with a maximum total area of 5000mm2. The thickness of each section may not exceed 25mm when measured perpendicular to the car centre line.
- Upper-left is a standard wing using the full height of the legality box, no centre support is used and so additional bracing would be needed at the wings base and/or thicker endplates which also carry the DRS hydraulics (Williams took this option in 2014.
- Middle-Top is has the same legality box but uses a central pylon for stiffness and to carry DRS hydraulics.
- Upper-right has the maximum legality box but uses twin pylons set at the maximum Y100 (200mm).
- Bottom-right is a 'Spoon' style rear wing with twin mounting pylons, the maximum height is set at 150mm in the centre but arches to a smaller height at the tips.
- Middle-bottom exceeds the maximum 150mm in the centre Y100 section of the wing and can have a range of flap sizes upto the maximum 150mm height at the tip.
- Bottom-right shows the difference between the geometry that was available in green (Y75) vs the geometry that will be available in 2016, marking in red (Y100)
|Mercedes did use a 'Spoon' design for both Spa and Monza this year, although the Monza wing wasn't strictly adhering to the 'Spoon' design as it stayed within the regular regulation box.|
Why the hell are you bringing up 'Spoon' wings Matt? Well funny you should ask, the two topics don't seem interlinked, however, they are. Sauber's last foray into the use of DRD was in tandem with a 'Spoon' style wing as they looked to further improve both downforce and drag reduction, mounting their stalling pylon under the mainplane.
Sauber C32 - An even better shot of the internal pipework associated with DRD via @SuttonImages #TechF1 #F1 pic.twitter.com/hl6HbI96Ud— Matt Somerfield (@SomersF1) February 21, 2013
Whilst I've generalised about the central pylon up until this point and only really referenced the Lotus design below  with its small vertical slits that blow latterally across the wing...
....there are other considerations to make in terms of the pylon's design, which will also have an effect on how the rear wing 'stalls' and recovers. Teams have, on the whole, moved toward a swan neck design for their mounting pylons, meaning that the pylon is slightly ahead of the rear wing structure, with the upper section arching over the top of the mainplane to meet with the DRS actuator pod. This is because the pylon itself can cause a distrubance to the airflow, causing seperation and reducing the wings ability to create downforce. Having said that, Mercedes still lead the pack yet run with a pylon design that connects under the mainplane, so, it can just come down to how you design the components to work with one another.
Furthermore, in order to maximise the shape and design of the rear wing endplates teams have been using the pylon(s) in order to house the hydraulic components required to operate DRS. This means that careful consideration would need to be taken in order that a compromise is met.
|Red Bull RB11 - DRS hydraulics are fed through the bodywork to the pylon, where they are fed through it to the DRS actuator.|
Last but by no means least there is also the possibilty of using either a twin pylon configuration which could stall a wider area of the wing or the mounting of another carefully shaped winglet under the mainplane in the Y100 zone. The latter would need to be shaped in order that it doesn't impinge on the actual performance of the rear wing but could also blow a much wider area of the rear wing.
What (I'm saying if you haven't skipped past the history lesson) is there is no one-size fits all solution, as always if teams do pursue Active-DRD they will all come up with different solutions. What I've given is a very basic overview and so I'm not for a moment suggesting it's a silver bullet that everyone will have, infact I'm not even saying anyone will have it. Moreover, I'm simply putting it out there as a theory, just as Craig did on Twitter last week..
There has also been a healthy discussion taking place on F1Technical on the matter too, with previous 'stalling' devices used in order to rationalise its use just as I have. If you fancy a look here is a link to the thread: http://www.f1technical.net/forum/viewtopic.php?f=4&t=23573Remember the DRS duct on the Lotus? I've just found a way to make it work reliably within the new exhaust rules! pic.twitter.com/nPGe0PjFTc— Craig Scarborough (@ScarbsF1) October 15, 2015
As this is a long winded post I've decided to summarise how DRD could be made active by the use of the new wastegate outlets below: