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31 August 2012
Mercedes WO3 Passive Rear Wing 'Device' (DDRS, Super DRS, F Duct)

Wet weather in Spa has put pay to a lot of the running the teams were hoping to do in order to evaluate new parts.

Mercedes bought a surprise package to Spa in the form of a drag reduction device much like the lauded Lotus device.

Due to the weather conditions getting shots of the WO3 in action were slim but as we can see from the images below the device mimics the effect Lotus are trying to achieve.



Just like Lotus an adaption to the engine cover has been placed around the airbox in order to recapture air along with any being spilt off throttle (This occurs when the opening can no longer receive anymore air and so the airflow tumbles back out and over the sides of the airbox)
Airbox Spillage being captured by these ducts also helps tidy up the airflow that may become turbulant and affect the Rear Wings effectiveness.

The air that passes through these ducts is then sent down the engine cover before being diverted up the Periscope to the Rear Wing.  Unlike the Lotus version Mercedes periscope stops short of the underside of the Rear Wing.  (It's unclear at present if this is part of the design process or a different Rear Wing will be used in conjunction with the device)



As the periscope was taped up (Due to weather) it's unclear how big or the orientation of the blow holes but what is clear is, if the periscope does indeed drop short of the Rear Wing the blowing effect may cover an increased area than the Lotus variant.


As I explained in my previous article the possibilities on offer with these devices are large and can be used to create additional downforce aswell as for drag reduction: http://somersf1.blogspot.co.uk/2012/08/bank-holiday-monday-musings-rear-wing.html

In short if I'm right by being able to blow the rear wing via these pylon holes it allows for the Rear Wing to run at a steeper angle of attack (AoA) this is because the holes decrease the boundary layer build up and so increase downforce.  As speed exponentionally increases the holes get to a point whereby they can't provide enough airflow for the wings AoA and so the wing stalls (Critical Angle / CL Max) Downforce is reduced and so is the drag.  This allows for the car to ultimately attain a higher speed (I'd predict 5-10KMH)

Mercedes will continue to use DDRS in tandem with this device thus aiding with further drag reduction whilst DRS is unavailable. 

The mainstream media still seem intent on calling these devices DDRS (Double DRS) or Super DRS as I first coined it.  For me that is a name that should only be used for the original Mercedes system as it requires the use of DRS for it's secondary usage to come into play.

The Lotus team simply call theirs the 'Device' so perhaps we should by using the acronym DRD? Drag Reduction Device?

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27 August 2012
Bank Holiday Monday Musings: Rear Wing Design & The Past, Present &Future of Passive Ducts, F Ducts, DDRS and Super DRS - Lotus E20

As much of the traffic to my site atthe moment centres around the Lotus DDRS/Passive F Duct system Ithought for my pre Spa Musings I'd talk a little about thepast iterations of such a system. 

We can go as far back as 2008/09 to seethe first signs of these devices emerging with both McLaren and Toyota fielding passive ducting on their cars for more co-efficient designs. 

The designs of all the systems have always centred around the premise of the central 15cm of the wing being free to allow holes. The Toyota and McLaren designs of 08/09 featured such holes in the15cm region which would increase downforce in the central portion of the wing by injecting airflow below the normal wing gaps. 

As we can see from the pictures below of the McLaren from behind at Monaco in 09 the slot gap projects the same width on the rear as it does at the frontal collection area. McLaren angled the wing fences on the wing in order to augment the airflow across the wing. The slot gap delays the onset of boundary layer separation caused by the wing being run at additional angle of attack, resulting in a downforce gain with the slot acting as a third slot gap separating the wing plane. The rear wing planes angle of attack and the size of the hole in the wing are crucial at higher speed. As the speed increases the air provided by the hole gets to a point where a blockage occurs, (ie no more air can be vented) this causes the boundary layer to separate and thus the wing stalls. 
In aerospace the term 'stall' is used in a different context to the way the F1 fraternity use it. In terms of an F1 wing a stall occurs when the angle of attack is too large (same as aerospace) whereas when an airplane wing stalls, lift is lost due to the critical AoA being exceeded and the flow separates creating drag.  This is where the major confusion occurs as principally when an F1 wing stalls just like an airplane it creates drag but essentially there is a resultant loss of downforce.   The loss of downforce makes the wing less efficient and so cancels out the drag further giving a top speed advantage of between 5-10km/h dependent on the system.

 Above: Toyota TF108 - Monaco 2008 you can see the central duct in the 15cm free zone
Above: McLaren MP4-24 - Monaco 2009 Shows the passive duct used by McLaren which was the genesis for the 2010 driver controlled F Duct

It is widely accepted that drag reduction is the desired effect of both passive and F ducts but it is entirely plausible downforce is also gained as a result of careful management of the rear wings angle of attack (AoA).

The F Duct systems of 2010 (Once again with McLaren at the fore, using their 2009 experience) were a development of this principle. Adding the driver as the controlling influence allowed the team to make the slots on the rear of the wing  larger meaning they could gain more downforce from an aggressive wing AoA whilst blowing the wing. When the driver covered the hole in the cockpit the airflow to the rear wing would cease and drag would be reduced.

 Above: McLaren MP4-25 - 2010 Slot gaps extend across the top plane of the rear wing

The FIA changed the rules in 2011 to stop the F Duct systems by placing a minimum radius of 100mm on the wing planes, this stops the teams from adding the slots that ran almost the length of the wing planes but the 15cm central zone still remains open to interpretation. Obviously with the allowance of DRS the FIA assumed that teams would no longer pursue this method of downforce enhancement / drag reduction. However the system that Lotus have been testing since Hockenheim uses these exact principles.

Lotus Passive Pylon Duct

With the 100mm Radius rule stopping the placement of elongated blow holes on the rear of the planes it would appear that only the original straight through style duct would be viable in order to create the F Duct effect (Like the Toyota and McLaren versions shown above).  However smartly the Lotus system takes cues from the original F Duct concepts but rather than using holes/slots in the wing planes these are placed in the pylon that connects the engine cover to the Rear Wing. The holes blow tangentially from the pylon across the wing span.

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.

Above: Lotus E20 - Hockenheim Showing the rear wing painted with Flo-Viz, due to the Flo-Viz you can see in the central section the airflow separating

Above: Lotus E20 Airbox 'Ears'

As I have talked about previously the 'Ears' are used as a way of recovering airflow when off throttle.  The main airbox entry blocks when off throttle and the air that usually tumbles over the side and disturbs the airflow heading towards the rear wing now enters the ear ducts.  This obviously helps by keeping the system in loop during the Braking and Turning phases generating more downforce.

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.

In order to see how Lotus (nee Renault) came up with their current system lets quickly look back at their 2010 efforts.  The team actually used two variants of the rear wing drag reduction system back in 2010, they ran the passive style system that McLaren used in 09 and then a full blown F Duct system. Their full blown system used similar Airbox ears we now see on the LotusE20. The pylon being used as a means of carrying the air to the under side of the Rear Wing also featured in the original 2010 designs but this was structural in the 2010 versions. This however must have given the team a head start in CFD and Wind Tunnel in terms of modeling the structures involved.

 Above: Renault R30 - 2010 (Hungary) Passive System
  Above: Renault R30 - 2010 Showing the similar Airbox 'Ears' being used currently on the Lotus E20
Above: Renault R30 - 2010 F-Duct System

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'

Above: McLaren introduced a Red Bull style Diffuser gurney in Hungary in order to aid the generation of downforce


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. 

Images Copyright: Sutton Images
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15 August 2012
The trouble at Mercedes

Mercedes are a company that have invested hugely in F1 over the last few years in response to buying the Championship winning Brawn GP. In terms of Mercedes interest in F1 they had for a long time aligned their selves with the McLaren team, having some of their SLR road range carrying the McLaren logo. Mercedes also owned a 40% stake in the McLaren outfit with McLaren effectively acting as their works team. Ron Dennis having moved across from the F1 team at the end of 2008 to focus on a road car project meant that the two had a conflict of interest. McLaren and Mercedes amicably agreed that McLaren would purchase back around 30% of the shares and so Mercedes found their way into owning the majority of the Brawn GP team (with only the directors of Brawn GP owning small percentage shares in the Mercedes GP team)

Brawn GP was the legacy of a hugely expensive project formerly owned by Honda who had also elected to buy the team from the well established BAR who in 1999 had bought the team from Ken Tyrell. This year (2012) is the third iteration under the Mercedes marque which as a project was supposed to bear fruit as a manufacturer in its own right rather than just be an engine manufacturer. (Just as its previous owners Honda were looking to do) The trouble is always one of transition, time and of course money. Lets look a further back down the line to see how Mercedes current struggles can also be attributed to the past and where they are going to go from here.

2009


2009 was a difficult time for the Brackley based team, on one hand they were winning races and taking the plaudits for building a fantastic car but on the other hand they were restructuring and losing staff to fall in line with the loss of Hondas money and support. 

In 2008 Honda had realized their car was a dog and switched their focus early to the RA109/BGP001 knowing a new set of regulations gave them a blank canvas on which to base their design. They also accrued some of the team that had been working within the Super Aguri team that had folded in 2008. This was believed to be pivotal in Honda's design approach for the 09 car with the Super Aguri crew rumoured to have bought the DDD concept to Ross Brawns attention (whilst others who left Super Aguri made their way to Toyota and Williams). Honda threw resources and money at the 09 contender although the Japansese marque will never be remembered for the success as Ross Brawn the man who lead the buyout had his name above the door. In fairness to Honda they didn't simply withdraw from the sport but looked for another source to continue their work and keep their employees in a Job. Several avenues were approached but eventually it was to be Ross himself who would take the the team on.

Honda continued to financially support the team well into the season with around 100 million still filtering to the team into 09. The team were unable to align themselves with a title sponsor in such a short time frame meant they attained sponsors on a race by race basis. This may not seem the most business savvy approach but can be a lucrative one if deals can done for each race. Richard Branson's Virgin brand was the one to be most associated with the team during the 09 season but again this was a case of sponsorship on a race by race basis although Branson would have had you believed otherwise (shrewd marketing on his behalf)

With the 09 season being the first in a new rule set Honda had obviously ploughed large resources into making the 09 car successful. The largest problem Brawn faced when trying to get the car to the Melbourne grid was the engine supply as Honda had no allegiances beyond their own works team they no longer had to supply anyone in F1. Ross initially went to his previous employers Ferrari but swiftly realized that integrating that engine into the car would be a monumental task. The next port of call was Mercedes at which point from the specifications it became clear fitting the Mercedes FO108W would be much easier and so began a partnership with Mercedes that would later see them become the works team. It's widely reported that although fitment of the Mercedes engine was easier than the Ferrari counterpart it still had compromises notably the CoG was raised and crank centre position was far from ideal. The team were desperate to utilize the gearbox designed in house as it's design was both light and centered around the utilisation of the DDD concept. Both Jenson and Rubens were vocal in their admiration for the Mercedes engine which was reportedly much more linear in it's power delivery giving much better driveability. The Honda engine was always well known for having a very peaky top end performance and this obviously showed when the team transitioned to the Mercedes powerplant. It remains unclear whether Honda intended to use KERS but the designs shown of the RA109 place the energy storage (batteries) lined up in series in the bottom of the nosecone. A novel solution considering the weight and cooling complications this may have had. http://www.greencarcongress.com/2010/11/hondas-f1-kers-motor-60-kw-21000-rpm-7-kg.html

The KERS technology was not passed onto the Brawn outfit and/or would have been difficult to implement with the Mercedes engine due to the crank position, cost and purely timing, KERS wasn't possible for the team to introduce in 09. As other teams struggled to utilize their own KERS systems Brawn were able to move ballast around their car but mainly loaded their bib/tea tray area with ballast echoing the weight distribution ethos that the RA109 equipped with KERS may have had. KERS packages in 09 weighed around 30KG's which is a substantial amount of weight when you consider being able to put this wherever you like in the car. The likes of McLaren & Ferrari had to place their heavy systems in certain places to utilize cooling and weight distribution.


It turned out that Red Bull would be Brawn GP's closest rival during 2009 with Brawn leading the charge from Australia and the DDD being the coup of the season finding a loophole in the regulations relating to diffuser overall height and using a section above the starter hole to create an additional deck in order to create more diffuser volume. This was much to the frustration of all but Williams and Toyota who too had similar designs and interpreted the rules in much the same way. Ross Brawn as part of the Technical Working Group (TWG) had throughout the draft stage of the technical regulations for 09 pointed out that the area should be looked at due to the potential it possessed to create downforce. He later argued when the teams tried to retrospectively ban Double Deck Diffusers 'I told you so'. The ruling by the FIA to allow DDD's was a huge frustration to a lot of the teams as they knew the lengths that would need to be taken to integrate it into their own cars. The development and implementation of DDD's would take several races and lead to a total shift in the development path most teams would need to take for the season. However it was clear that the BGP001's diffuser was the silver bullet and needed for the fastest package. Red Bull were seemingly the most frustrated having designed what was essentially the quickest non DDD car. Adrian Newey's bug bear was not that he hadn't come up with DDD it was that he could neither get it banned or quickly adapt his RB5 to have it, due to them adopting pull rod rear suspension. Whilst the Red Bull team poured resources into integrating DDD the Brawn team just tried to stay consistent as they couldn't afford the massive cost of a development race and perhaps capitalized on the change from Bridgestones grooved tyres to a more traditional slick tyre whereas others struggled. 


It turned out that the early advantage that Brawn got in 09 was enough to take both Drivers and Constructors titles making only minor changes to the BGP001 throughout the season. The BGP001 considering it's late change to Mercedes power remained very reliable with the team only having 2 retirements all season only 1 of which was a mechanical failure (Rubens Barrichello at Turkey with a rear suspension failure)

Throughout 09 Brawn had realized that the high chassis / nose / suspension of the RB5 was worth pursuing for 2010. They ran a sight bar / nose ridges to test during Free Practice sessions in 09 in order to assess whether this was the right design process to follow. It's difficult to know from the outside how much effort Brawn had to sacrifice on their 2010 car in order to win the 09 championships.
Mercedes decided to purchase Brawn GP but the announcement wasn't made until after the 2009 season had concluded. 2009 had been a hard fought battle with Red Bull and although the team took the title, it had come at the expense of balancing the development of the 09 car further into the season than perhaps was really wanted.

2010




The WO1, Mercedes first car in F1 since the 50's was flawed for many reasons although the Brawn GP team had been world champions in 09 they neither had the resources or money to contest the battle for 09 and produce another championship winning car for 2010. When design focus was needed to be placed on the 2010 car during the 09 season both Jenson Button and Rubens Barrichello were at the helm of the BGP001 neither of which drove in Mercedes first season compromising the W01 with traits that perhaps their new driver line up of Michael Schumacher and Nico Rosberg wouldn't like. Michael returned to the sport in 2010 after a 3 year absence in which time he spent the first year as an advisor to Ferrari and continued his motorsport journey on two wheels until at which point he had an accident and injured his shoulder. It was afterall this injury that had stopped his return for Ferrari in 09 for the injured Massa at Ferrari and reignited Michaels passion to be in F1.
The DDD diffusers that were the catalyst for Brawn GP's success in 09 were already now fully integrated into the lead teams packages, aided by Exhaust blown diffusers some of the teams now had a huge chunk more rear downforce than the W01.

Several rules were bought in, in order to make adjustments from the rules first laid down in 09:

The front tyres were reduced in width from 270mm to 245mm in order to remove some mechanical grip from the front of the cars.
A new points system and qualifying process was bought in to both balance the larger field and add further entertainment for the fans.
Refuelling would also be excluded. This would see teams carrying around 160-180 Litres of fuel from the start of the race rather than the 70-90 Litres they carried in 09. This in itself required a major rethink in order to balance the requirements of qualifying and the race and selecting wheelbase/weight distribution correctly would give one team more of an advantage than it's competitors.
The 2010 season saw all the teams agree on an exclusion of KERS due to the heavy costs involved for the 3 new teams entering the sport.


The largest changes from the BGP001 to the WO1 came in the form of the higher ridged nose/bulkhead as I alluded to earlier that the team had taken a cue from Red Bull and in a latter upgrade a blade style roll over hoop with twin airbox entries either side.

It was McLaren who stole the limelight in regard to innovation for 2010 with their F Duct system which reduced drag when the driver placed his knee/hand over a cockpit aperture moving airflow normally designated for the engine cover exit and instead blowing the rear side of the rear wing plane via the shark fin style engine cover which was attached to the rear wing plane. All teams realised that the device was a very clever interpretation of the rules and set about designing their own variant. This turned out to be a protracted battle as McLaren's tub was designed with this in mind whereas the other teams were not. Mercedes decided that they couldn't effectively develop a close loop (driver operated) F Duct system into their package without further compromising their current aero (due to the low slung blade roll hoop) and so set about adding an open loop (passive) rear wing drag reduction duct. 

They teased everyone at first with a loop that went from the main plane to top plane but it would appear no other ducting lead from other areas of the cars to this section. The design they eventually used was remarkably similar to a design that McLaren ran in Monaco 2009 who cited this to be their original inspiration behind the current F Duct. Ducts like these are activated by air speed and so when the car reaches a certain velocity the air moving through the duct to the slots on the rear wing plane reduce drag. If indeed this arrangement was passive then I see no reason that Mercedes having experience with the device couldn't fit it or a similar system to the W03 to reduce drag on straights that DRS is unavailable just as Lotus are looking to do with their DDRS system. The slot and ridges are formed in the central 15cm free zone that allows for the DRS pylons etc and so should still be legal under the 2012 regulations.

2011


This year was the first year proper for Mercedes as a team and with a car designed with Nico and Michael in mind. Gone was the controversial blade style roll hoop/airbox in favour of a more conventional one. Even though both Force India and Team Lotus had taken cues from the W01 with their 2011 challengers and ran with blade style hoops. Brawn and the team cited the blade hoop as being part of the compromise of the W01 causing CoG issues. The double decked diffusers of 09/10 were no longer available to the teams in 2011 being banned by the FIA.
With DRS taking the place of 2010's F ducts systems in order to reduce drag, the aerodynamics of the car before the rear wing would be paramount. Mercedes unlike most of their competitors positioned their DRS actuators in the endplates leaving the wing planes free of any obstructions or moving parts. Mercedes did however have problems both the actuation of DRS and problems with the wing aerodynamically especially it would seem with Michaels setup. A larger angle of attack chiefly to be blamed with aero balance being affected when DRS was deactivated in the braking phase. As the top plane snapped shut downforce should be restored allowing a stable turn in. However as in aeronautics if you run too high an angle of attack the wing stalls and loses aero efficiency. Both car stance (through suspension setup) and AoA can be blamed for the stall that was occurring, as soon as the wing pitched to the right angle the airflow reattached and downforce is restored.

Perhaps one of the most controversial aerodynamic elements at the end of 2010 and carried on rumbling into 2011 were the flexi front wings being used by the Red Bull and Ferrari teams. Most of the teams found it incredible the wings were making it through deflection tests but even when the FIA increased the load/deflection tests they still passed. McLaren's 2011 contender (MP4-26) also ran with a Front flexi wing but not to the same degree as the RB7. Mercedes were once again late to the party and it was Germany before the team started testing/using their own iteration. Whilst on the subject of front wings Mercedes really played with 2 front wings for the start of the season with one of these having a hole in the main body of the wing. See Craig Scarboroughs article on this: http://scarbsf1.com/blog1/2011/03/11/mercedes-w02-new-front-wing-analysis/

Above: Front Wing with hole in the main element

The Sidepods entries were angled inward toward the tub encouraging airflow around the Sidepods. The nosecone took further influence than the W01 from Red Bulls designs with a higher much flatter nose in order to drive more air under the car and even more pronounced ridges running longitudinally around the suspension.

What i found strange from the original test car were the sidepod airflow conditoners were very small (vertically) of which my only prognosis was they wanted to get as much more air toward the rear wheels rather than concentrating the flow at the sidepod itself. These were replaced at the last pre season test with more conventional height conditioners.

The W02 took the W01's moving wheel base throughout 2010 and decided on a stunted short wheel base. The short wheel base could attribute to some of the issues the team had both with CoG, aerodynamic deficiencies and tyre degradation. With Pirelli re entering the sport and taking over from the out going Bridgestone era the focus for tyre degradation in 2011 was always destined to take a front seat. Tied to this was the FIAs introduction of a weight distribution ruling in which mandates a 46/54 split. This was done so that teams didn't steal a march on another by stumbling across the perfect tyre balance and causing a development war between the teams to find the perfect balance. Although the teams had decided to omit KERS from their cars in 2010 it made a triumphant return in 2011 and Mercedes had been working on improving theirs with the system also reduced to around 24kgs.


Above: The original Mercedes WO2 Exhaust design
Their original exhaust much like their rivals exited rearward but seemed to pointed further outward toward the wheel/tyre than say Red Bull perhaps in an attempt to seal the diffuser edge. The second version of their exhaust taken to the last pre season test was much further forward, exiting out of the side of the Sidepod encouraging airflow across the floor toward the rear of the car enmass with the airflow already pushing around the side of the Sidepods. The movement of the exhaust further forward could also be in response to their short wheel base. A small vertical strake in front of the wheel helped to navigate the airflow inbound toward the region above the diffuser.
Above: The WO2's second version of the exhaust 

It took Mercedes until Valencia to converge on the Red Bull solution who had their exhausts exiting much more rearward and enclosed in a tunnel above the floor to the outside edge of the floor sealing the diffuser much further back and eliminating the effects of tyre squirt (see my tyre squirt article). Even with the FIA curtailing the off throttle effect this remained the most effective way of getting a diffuser sealing effect.
Mercedes GP found in 2010 as with the other Mercedes powered cars using the exhaust plume to enhance downforce was unpredictable. This is most likely down to the mapping constraints and general attributes of the Mercedes powerplant in comparison to the Renault, Ferrari and Cosworth power units. With throttle sensitivity and overheating of bodywork all being issues for the Mercedes powered cars. The problem with modern F1 is the lack of testing and the cost implications of taking test parts to the circuit. On the other hand some teams throw caution to the wind and will take more physical parts to a race weekend to test than others. The problem with assessing exhaust plume airflow in simulation is getting the simulation right after all the exhaust is ballistic and changes based on throttle input make using the exhaust plume an aerodynamic advantage by exiting into atmosphere very much a driver controlled entity. Enter Off throttle blowing something not only the Mercedes teams were doing but something that definitely helped those using Mercedes engine to narrow the gap to their rivals. Using off throttle blowing helps to keep a continuous flow over the diffuser, energizing the boundary of the diffuser and helping to draw more air through the diffuser.

 Above: (Top & Middle) shows the solution's Mercedes used to enhance EBD running an exhaust channel on top of the floor at the extremities of the diffuser. (Bottom) Shows the heat treatment added to the exterior of the diffuser to help with heat demand placed on the area by the exhaust position.  Mercedes version of EBD ran much shorter on the floor than say the Red Bull variant which may be due to exhaust tuning requirements of the Mercedes engine.
2012

Mercedes began their 2012 campaign in quite a strange manner using the W02 at the first test. This allowed the team to correlate tyre data from 2011 with the new Pirelli compounds of 2012. Apart from tyre data, testing with an old car offers little benefit as the new car differed significantly in wheelbase. The WO3 for all in tense and purposes should have sorted most of Mercedes 2011 problems with a years running on the Pirelli tyres, a new simulator and an enhanced team with new members of staff during the design phase of the WO3.
The largest innovation at the start of this season came from the Mercedes team in the shape of the Double DRS (DDRS) system. Part of the system had been tested at the end of season test in Abu Dhabi but most passed it off when the drivers complained of difficulties when entering the braking and turning phase. This device then muted the 'W' duct (as the airflow pattern looks like a W) used the driver cooling hole as a method of passively blowing the front wing. Air entering the cooling slot passes down the wing pylons and out of a slot on the underside of the wing. However when this test took place they were using the WO2, for the WO3 the team had also integrated pipes which run the length of the car joining the Front wing with the rear wing meaning that DRS plays a part in the activation of the system in a similar manner to the original F duct concept found on the McLaren etc during 2010. The Lotus team protested DDRS but the system was deemed legal due to the driver not being part of the activation process like the original F ducts demanded and rather the DRS being active or inactive provided the switch for drag reduction. If you have followed my work on Final Sector since the start of the season you may see that I don't fully subscribe to the Mercedes Front wing DDRS function others do.
How i believe Mercedes DDRS works


This is my theory and is based upon techniques used in aircraft like blown flaps, circulation control wings, boundary layer control etc. Below I'll aim to explain my ideas further/better than I did in my original article: http://finalsector.co.uk/mercedes-super-drs-f-duct/
I must add that this is a theory and please feel free to dismiss it over the conventional theory.

My theory is based on the slots under the front wing making the wing work when blown. This is based on the assumption that when Mercedes originally tested the 'W' duct it was in order to create additional downforce aswell as reducing drag. Wings can only create so much downforce, this can either be done by dimensionally adding more wing or by increasing the angle of attack. The size of the flaps available to F1 designers is heavily restricted in order to limit the downforce available, they can add gurney flaps but these will add drag and so on the front wing are usually limited in size. Wing angle of attack (AoA) can effect how much downforce is generated but once again at the compromise of drag. I'd guess 15 degrees is about the stalling level of a wing (ie the point at which it won't create additional downforce and stalls) if you were to blow the rear face of the wing you can elevate the wing angle by perhaps another 5 degrees before it stalls. This gives you the advantage of being able to run a higher AoA than if you didn't blow it, resulting in a net increase in downforce.



Above: Cascadeless Front Wing adopted from Montreal onwards

Since Montreal, Mercedes have run their front wing without the cascades which again highlights that they may have been creating too much front end downforce and the cascades creating drag as a net result. (They also changed their wing pylon design to a very McLaren-esque design) I believe the wing from the WO2 with the hole in front of the wing planes paved the way for this, with the designers wanting the air to be forced in behind the main planes to allow a higher AoA. Being able to do this without the need for the through hole would be more efficient.

Above: Mercedes WO2 Front Wing with blow through hole
So how does this all work with DRS i hear you say well i believe the original 'W' duct is intrinsically linked with the DDRS tubing from the rear wing:
Airflow captured in by the nosecone cooling hole is sent down the wing pylons and exits underneath the wing allowing for a higher AoA


When DRS is deployed the airflow that usually goes down the pylons toward the front wing is sucked/pulled past and sent along the tubing to the rear wing.

Above: Image of the tubing that runs inside the Sidepod from the front wing through to the rear wing endplates
This has two effects: it augments the airflow around the DRS flap by laterally blowing across the underside of the top wing plane enhancing the DRS effect but more importantly without the blown effect on the underside of the front wing, the wing has too high an AoA and stalls shredding both downforce and drag.

Some of Nico's quickest lap times at the start of the season saw him deactivating DRS prior to the braking phase which if my theory is correct would see the front wing becoming blown restoring front end downforce and balance for cornering/braking.

Mercedes DDRS is really a qualifying enhancement and if my theory serves correct becomes more of a hamper as the race goes on.  This is due to pitch angle, as the fuel burns off during a race the AoA on wings alter ever so slightly which puts the car through an evolution process.  This could be part of the reason for Mercedes tyre struggles (again speculation).

Although initially the Lotus system was hailed a DDRS it would now appear it is very much a passive F duct system much like the one that Mercedes ran on the WO2 so if Mercedes are prepared to take their closest championship rivals on there is no reason why they couldn't employ a similar system to reduce drag on the lower plane like Lotus: http://somersf1.blogspot.co.uk/2012/08/lotus-e20-passive-f-duct-system.html (TDRS anyone?)
DDRS may have be becoming the WO3's Achilles heel as any upgrades placed on the car will need to be balanced with the aero shift that is created by the device. This however is not the largest problem in play for Mercedes and that more likely stems from the polar opposite of the WO2 with the current car having a very long wheel base. The wheelbase can effect everything from suspension geometry, to tyre wear, to how downforce is created amongst many other things. The WO2 suffered in terms of cooling due to its wheelbase as the Sidepods were too small compromising internal dynamics. This season the Sidepods are much bulkier to both accommodate the additional cooling requirements and the DDRS tubing. The boundary layer build up along the top surface must be fairly significant due to the length of the Sidepods. However having the exhaust exit on top of the Sidepod will at least enhance the airflow travelling along the top of the sidepod.
Unlike other teams that use the Coanda style exhaust positions and have adopted the vortex generator fins on top of the Sidepod Mercedes don't need these as the airflow doesn't need to be destabilized or guided in a downwash effect as the Sidepod remains fairly high to the rear. Mercedes haven't upgraded their car at the rate of their opposition with their major upgrade package featuring at Monaco: http://finalsector.co.uk/monaco-gp-technical-roundup/ and the race after in Montreal saw the team drop the front wing cascades most likely in response of balancing the upgrades from Monaco.

Mercedes have a difficult decision to make with now only 9 races of the season left, unlike their counterparts Mercedes have stood firm in their design ethos whilst others have converged on very similar exhaust design paths. This is something that the team did in 2011 too leaving them trailing to their rivals. They claim that by not adding upgrades they can better understand the effects of the Pirelli tyres, this all sounds well and good but whilst you stand still in F1 your are actually moving backwards in comparison to your opposition. Mercedes need to make a decision on where they need to finish this season as upgrades are the only way to stop the like of Williams, Sauber, and Force India overtaking them in the title battle. They could do the same as Honda in 08 and shift focus now to their 2013 contender but this could be at the cost of lucrative FOM money.

Conclusion

From the outside looking in it would appear that Mercedes internal processes take too long to implement leaving them at odds when either following their own design path or trying to converge on others. This problem is systematic and stems from the gestation period between Honda and Mercedes as highlighted here by Ross Brawn after a hard fought 2009 campaign:

"In the interests of fairness, we simply said that every department had to lose 40 per cent," said Brawn, something regretfully. "It was as crude as that. We had no other mechanism to go through the company and say, two from here, five from there."
A lot of good people were lost in that cull, not necessarily big names, but engineers that were a crucial part of forming a team's backbone, that helped ensure their departments could run with a certain degree of autonomy. The group that was left was not only shellshocked by the cull and the loss of several key working relationships, but had to establish a whole new dynamic.
Into that mix throw in the departure of a senior member of the engineering staff - Jorg Zander, who left early last year - and it's not really so surprising in hindsight that the car was a little unadventurous. Its gearbox, for example, was too short to make really aggressive use of the twin diffuser”

As Ross alludes to here Brawn GP didn't simply lose tea ladies in the cull, the staff lost were integral to the team and meant a total change in philosophy this would then be followed by the introduction of Mercedes who would want processes done their way. Mercedes like Honda before them will be thinking long and hard about their involvement at team level and the rewards team ownership brings. As I have been writing this article word has spread that Mercedes intends to step back from it's team involvement from 2013 onwards which shows that the money men in Stuttgart now realise that just like Renault, F1 can bring success without a having the need for a team.

All images used are copyright their original owners: Sutton Images / XPB Images / BAR555 / motorsport.nextgen-auto.com/  / Motorsport.com / Lat Photographic
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03 August 2012
Lotus E20 Passive F-Duct System (DDRS/Super DRS) – Part 2


You may well have already read my previous article on my feelings regarding the Lotus DDRS system http://somersf1.blogspot.co.uk/2012/07/lotus-e20-ddrs-hockenheim.html, as always the problem with not being able to see these items in the flesh leaves doubt over their actual purpose. As more images have become available it's become clearer that my original thoughts on the system although perfectly valid and usable are actually flawed. The trouble with fluidic switching systems is that there are so many ways in which you can move air from one location to another that the waters muddy.

Compounding this, Lotus had already stated that their system utilises the same loophole that the Mercedes DDRS system works within (ie using the DRS movement as a part of the flow adjustment for another device). It is plausible that is a Red Herring with the addition of the periscope simply acting as it's own device reducing drag by blowing the underside of the Rear Wing's main plane reducing drag passively above a certain speed threshold and then when DRS is activated it simply augments the DRS effect. I'll explain this first and then go on to explain how both this theory and my original one could be combined.



As we can see in the images above small slots in the periscope blow the central section of the main plane reducing drag in that region of the wing. (Flow Viz is splayed in this region denoting the reduction in drag) This concept mimics the original F Duct principles in how drag is reduced on the rear wing but falls short of being as powerful. The original F Ducts had much larger slots on the rear wing plane in order for the drag to be reduced over a larger area. The original F Duct also required the driver to act as a switch effectively turning on or off the rear wing, this was outlawed as part of the regulation change back in 2011. The Lotus system is instead tuned to reduce drag at a certain speed by specifically designing the engine cooling outlet. At lower speeds the air consumed by the airbox inlet and ear ducts can escape through the engine cover cooling exit. As the car reaches higher speeds the air consumed becomes more than can be effectively exhausted from the cooling exit and so air spills up the periscope toward the rear wing reducing drag on the lower wing plane.
The rules were amended at the end of 2010 to stop the interaction of shark fin engine covers with the wing planes and DRS was introduced in response to the teams drive to reduce drag and increase overtaking. With DRS now moving the whole top element creating a union with the engine cover would obviously be very difficult anyway.  The periscope however doesn't join to the wing frontally but on the underside and so circumnavigates this rule.

Using the periscope to blow the bottom wing plane allows a dual drag reduction system with the lower plane being blown as soon as the car reaches a pre determined speed and DRS obviously adding the larger drag reduction element as and when it's activated. Passive F Ducting to the rear wing will provide a marginal advantage during qualifying where DRS is unlimited simply boosting the DRS effect but it's during the race where the system should give Lotus the largest advantage. On circuits like Spa and Monza they will be able to increase their wing angle of attack creating more downforce during cornering and have less drag on the straights than their counterparts where DRS is unavailable.


The addition of the Airbox Ear ducts are as I mentioned in my previous article paramount in terms of balancing the system due to Airbox Spillage. As the driver comes off throttle airflow is impeded in the airbox entry and so tumbles off the sides of the airbox down the engine cover creating a turbulent airflow toward the rear of the car and most importantly disturbs the airflow around the rear wing. The ears that Lotus have employed capture this airflow in order to keep the airflow heading toward the rear wing with a laminar flow which in turn will help create downforce more effectively in the braking and turning phase (Credit Gordon Mccabe - http://mccabism.blogspot.co.uk/2011/10/airbox-spillage-and-fluidics.html)

Pit Falls & Problems

Although McLaren were the first to introduce the F Duct in 2010 it's widely regarded that once integrated that the Renault team (now Lotus) had the most effective F Duct system. This obviously puts them in great stead in terms of understanding how best to utilise such devices. The problem with a passive system over a controlled system (like the original F Duct) is that the system is very much dependent on airspeed through the airbox. This may cause problems in the form of tunabilty especially when we consider the difference between the ability of a car during qualifying with a low fuel load and that of a car full of fuel. We also have to consider the high speed nature of circuits like Spa and Monza have corners with high speed exits and so reducing drag on corner exit as the passive duct inadvertly activates could be catastophic. This means that the Periscope Duct needs to be tuned to activate at a relatively high speed and as such won't have the same drag reduction capability the older F Duct did.

Combination of the above with my original theory

If we take the team at their word that the system employs the DRS as a lever to leverage another element in the system I believe that both variants of my thoughts could be in play. The problem with this is that we are yet to see a close image of the DRS open in order to establish if the wing covers any holes in the wing plane.

This would work by exhausting the airflow from the airbox inlet through the cooling hole and as it the exit becomes too small for the airflow exiting the air moves up the periscope and reduces the drag on a portion of the lower wing plane. When DRS is activated and a hole is opened on the rear wing plane a more positive draw would be created on the airflow from the airbox inlet drawing more air up the periscope and out of the slots. This would increase the effectiveness of drag reduction on this region giving a more positive DRS effect. I believe this offers the more balanced effect with a transition phase of drag reduction from both avenues.

In Summary

Until further evidence presents itself the exact operation of the device is speculation but it's application is something I'm sure the other teams will be looking closely at as in a year where the grid is so close even the smallest advantage could play a large hand in the results of the latter races. McLaren have already hinted that they haven't ruled out the possibility of such a system before the end of the season. One thing is however clear that systems linked to DRS won't be prevalent in 2013 as the teams have unanimously voted to outlaw them. This will be passed to the technical working group (TWG) who will work with the FIA in order to constrain such usage by adjustment of the regulations.  This however doesn't prevent the usage of the passive element of the system via the pylon being exploited.

Credit to Nick McDowell for the image pointing out the slots in the periscope


Original Images Copyright Sutton Images (www.suttonimages.com)
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