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19 Oct 2015


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)

Back in 2010 McLaren arrived to pre-season testing with what they code named the RW80, but was latterly dubbed the F-Duct by the mainstream media.  
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 system, whatever you choose to call it, had a scoop mounted on the upper surface of the chassis, with ductwork passing through the monocoque to the rear of the car.  Meanwhile the air box was divided, with some pipe work responsible for the usual task of intake air and cooling whilst the another made its way toward a junction.  This junction split, with pipework feeding both the rear wing and the outlet just above the beam wing.  This was made possible by the connecting engine cover and slots placed on the rear face of either the mainplane or top flap (each team chose differently dependent on how they wanted to stall the rear wing).
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'
Under normal conditions airflow passing through the airbox duct would pass down through the engine cover outlet.  In order that the wing 'stalled' / drag reduction took place the driver would place his hand/knee (dependent on the car) over a hole in the cockpit, which in-turn created a switching effect at the junction (fluidic switch) causing the airflow to pass down the pipework to the rear wing through the slots on the rear wing, interrupting the normal flow pattern and 'stalling' the wing.
Here's an overview of how the F-Duct system worked.  When not in operation air flowed through the duct astride the cockpit and into the cockpit via the aperture, the pipework at the junction was shaped that when inactive the airflow from the airbox passes down through the neutral feed.  When activated by the driver (places his hand/knee/leg over the cockpit aperture) the airflow moves down toward the junction and the airflow switches, to supplying the rear wing.  NB Green denotes active airflow, whilst Yellow denotes no supply.
Outlawed by the FIA in 2011 owing to the danger of driver interaction it was replaced by DRS (Drag Reduction System), which was initially, during qualifying, unlimited in its use, whilst in race conditions it can only be used in 'activation' zones and only when a driver is 1 second behind the one he trails at the detection point.  It's use has been somewhat diluted since its introduction in my opinion, with the length of zones increased/decreased throughout race weekends in the past in order to facilitate better racing.  This often led to teams carrying numerous flap sizes and having to test their vMax in order to decide which way to go for qualifying and the race.  With the zones rigid in their length throughout race weekends it has become somewhat of a formality that the chasing car will overtake and is now moreover a tool to return the drivers to their status quo dependent on the tyre wear, rather than a tool to create overtaking opportunities.

In 2012 Lotus looked into another option to reduce drag, which they simply dubbed the 'device', I decided to call it DRD (Drag Reduction Device) as the mainstream media (Sky and the BBC) had begun confusing fans by calling it Double DRS (DDRS), an acronym already in use with Mercedes employing a drag reducing device that used DRS to 'stall' the front wing.
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
DRD was tested repeatedly by Lotus throughout 2012 and others joined them, with Mercedes, Sauber and Red Bull all trialling their own versions (albeit I was never really convinced that Red Bull were doing the same thing).  However, it never really reached its potential and featured in just one race, when Kimi Raikkonen gave it an outing at Silverstone.  The problem with DRD was it was passive, unlike the RW80/F duct it relied solely on air speed to create the switch, which made it difficult to tune.  The problem was speed, set the threshold too low and it would create an imbalance during cornering, too high and its effect was nullified by the additional weight and complexity of the components. 

So, come on Matt, why are you dragging all this up again?..

Well, if we take a mixture of both the RW80 switchable concept and DRD blown pylon it is entirely plausible the introduction of wastegate exhausts may have inadvertently reopened the door to the blown wing.  There are undoubtedly several ways in which this could work (trust me I've drawn several), but I've chosen perhaps the easiest to explain in order that we get the idea out on the table.

Firstly let's talk about the wastegates function, which is to relieve boost from the turbine when it exceeds the requirement.  F1 Powerunits have electronically controlled wastegates, of which the ECU are in command of and can specify changes based on differing parameters.  Therefore it is entirely plausible that you could utilize a low speed wastegate and high speed wastegate, with the low speed wastegate opened up until a given rpm or a steering wheel override command is deployed by the driver.  Furthermore, as the Turbo is supplemented by the MGU-H whilst the wastegate is in operation you can still keep the turbo in the optimum operational window.

Safe in the knowledge that you now have a method with which to switch airflow at a given speed you can once again set about stalling the rear wing.
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.
The wastegate pipe is shown in red, whilst the ducting sleeve shown in green is hollow, allowing airflow (blue) to be pulled through the sleeve when the wastegate is in use.  This image is only being used for illustrative purposes there would clearly have to be some geometric shaping of the sleeve in order for it to fulfill its purpose.
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.

Trade-off

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.
Red Bull RB6 - You'll note how much wing angle is used here in comparison with the almost ironing board configuration used by Red Bull in 2015 (above).  The ability to 'stall' the rear wing after exiting the corner means you get maximum downforce during cornering and a reduction in drag for an increased top speed when the DRD is active.

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.
Above is a graphical representation of just some of the options available to the teams past and present.

  1. 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.
  2. Middle-Top is has the same legality box but uses a central pylon for stiffness and to carry DRS hydraulics.
  3. Upper-right has the maximum legality box but uses twin pylons set at the maximum Y100 (200mm).
  4. 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.
  5. 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.
  6. 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.

Whilst I've generalised about the central pylon up until this point and only really referenced the Lotus design below [4] 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.
Whilst the pylon used on the E20 met with the underside of the mainplane, both Sauber and Mercedes trialled designs that fell slightly short.  Furthermore Mercedes trialled a design very much in vein of the RB6 F-Duct we saw earlier from the Monza images where a duct sat quite a bit below the mainplane.

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.


In Summary


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=23573

In Brief

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:
 
At low speed the wastegate is opened, with the MGU-H being used to fulfill its task of keeping the compressor spooled.  The plume (red) from the wastegate exhaust entrains the airflow flowing through the ducting from the airbox (green) allowing the wing to operate at its normal downforce level.
Once the driver has exceeded a predetermined rpm threshold the wastegate closes, the airflow from the airbox no longer travels through the lower outlet as its path is more constricted, instead it passes up the pylon and is ejected in a way that destabilises the airflow that normally attaches to the underside of the wing, causing a 'stall'.  This allows the teams to run with a more aggressive rear wing angle of attack, creating more downforce for cornering as they know the drag can be shed for the straights.
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15 comments:

  1. Matt you must be a technical advisor for a racing team..just leave, Scarbs must be an idiot he never clearly explains anything to the fullest like you!!!!

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  2. Elaborating on a point half-made in that other thread: Activating the duct based on speed is difficult and limited to speeds above the circuit's fastest corner. An alternative aggressive strategy totally under driver control could be:
    Set up gears 1 through 6 so that they can cover everything from 0 to 300km/h. Those 6 operate normally. Then set up 7th to operate between, say, 270 and 340km/h and 8th to operate between 200 and 270km/h (so shorter than 6th and 7th). Now make 7th and 8th gears that always open the second wastegate, which only opens in that case.
    Then the driver can activate his f-duct at will at any point above 200km/h (going quickly from 5th to 8th if needed), while always having it on above 300km/h, which should be faster than any real corner in the season. Lifting the throttle before braking deactivates it to avoid performance losses in the initial phases of braking.
    You have to stretch gears 1 through 6 (but not much more than Mercedes did in 2014), but it means using the duct for a much longer portion of the lap in almost any circuit, plus a simpler activation mechanism, plus activation (mostly) only on demand.

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    1. Hi Hollus, thanks for stopping by and for posting a link to the article on F1Technical.

      Although I wouldn't rule out your implementation of gear ratios it's in opposition of how I see Active-DRD working. I don't want to open the wastegate at higher speeds to trigger DRD instead I would open the wastegate at low speeds to deactivate it.

      DRD inactive (low speed): Airflow enters the airbox, the wastegate is open so a plume pulls the air through the exhaust sleeve

      DRD active (above the highest corner exit speed): the wastegate closes and the airbox airflow makes its way up the pylon(s) and blows laterally across the wing, causing the stall.

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  3. Great article. Point of clarity please...controlling intermittent wastegate exhausting is a challenge; once done however, are the gasses sufficient to affect the aero er... properly/effectively/long enough?

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    1. Thanks, you aren't using the wastegate gases to 'stall' the aero they are used at low speed to entrain the airflow through the neutral feed. As speed builds the wastegate is closed and airflow from the airbox is fed through the pylon(s) and is ejected laterally into the rear wings airstream, causing separation and a 'stall' just as the F Duct did.

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  4. If the wastegate can't be controlled independently it will be extremely hard to use them to stall the rear wing. The moment you are about to brake at the end of the straight, as you let of the throttle the wastegates will open....hence stall your rear wing...during braking and cornering...bad idea. BUT, if you can control them idependently (looking at the first image in this topic) lower pipe controlled normally as of today with center pipe for exhaust from the turbine. Then you can use the top pipe to activate the drag system. You can add a loop in the program that detects if being at full throttle plus other inputs, therefore full acceleration during straight line. You can also link it to the "push to pass" or "overtake" which opens all the power available from MGU-K and MGU-H. In this scenario the turbine must be going at full speed and the wastegate must be open to keep it from overspooling. So during this period you have a constant gas flow through the top pipe that will stall the wing and help to pass.

    Great history lesson Matt
    Thanks!

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    1. Ah but I'm proposing the opposite, the wastegate is entrain in flow through the lower neutral outlet at low speed. At high speed the wastegate closes and the airflows makes its way up the pylon(s) as this is an easier path for it to navigate, which in-turn causes the 'stall'.

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  5. Ah DRD, an old friend with big ears has returned, stirring fond memories! This is a great discussion piece and merits much discussion. One thing though, if you are using the ECU to manage waste gate operation for Active DRD, does this not constitute a preprogrammed moveable aerodynamic device?

    Great piece as ever 👍

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    1. Thanks David :) the wastegate is part of the powerunit regulations thanks to the 2016 regs, creating a fluidic switch system with no moveable parts that uses it can't be classed as a moveable aerodynamic device, otherwise we'd be banning exhausts too.. ;)

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  6. So this will put customers like Williams at a disadvantage? But how big could this disadvantage be?
    Thanks!

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    1. That depends on their development of said system and/or the specification of the PU they're using. I'd expect gains of around 7/8kph on the straights and beyond that for well developed systems but it's the additional downforce that can be grabbed from higher wing AoA's that would also help lap time..

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  7. Wouldn't that create a problem, while braking from high speeds? Sure, the wastegate would eventually open after reaching lower speeds, but at the start of the braking, the stalling would be active, which would cause quite a bit of instability, when it's badly needed. Or am I missing something? :)

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Whilst I'm trying to keep atop of the blog you may have noticed of late that there is less content appearing. For those of you that haven't realised, most of my work has now been moved over to Motorsport.com where I'm working with Giorgio Piola.

I'm still doing the technical image gallery for each GP with the continued support of friend of the site Sutton Images. However, as always my time is limited and so this might not be updated as quickly as it once was, so keep checking back.

As some of you may have found out already I'm also working with the Missed Apex crew on their podcast from time-to-time, either doing race reviews or dedicated 'Tech Time' shows.

I've embedded the latest version of the podcast below and will update this a frequently as I appear. However, please head over to Itunes if you want it to appear in your player when episodes are available. The show is great to work on and has a great lineup of 'regulars' but has also enticed some bigger names recently too, with Will Buxton and Bradley Philpot on shows during the summer break.


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