Following Lotus’ use of DRD in British Grand Prix, Mercedes tested their updated DRD system in Germany GP practice. The basic idea of Mercedes DRD is similar to that of Lotus, although the mechanism for turning on/off the air switch might be different.
Instead of having two ears besides the airbox as Lotus did, Mercedes has two additional inlets at the back of airbox. This is easily fitted as Mercedes has integrated some removable design to their bodywork around roll hoop this season. The combination of a big and a small inlet may act as the control system for the air switch.
In terms of outlet, there are two outlets with the upper one below the main plain of the rear wing and lower one below the monkey seat/ beam wing. Above a certain high speed, such as long straights and high speed corners where less downforce is needed, the upper outlet switches on. The air blowing out under the rear wing disturbs the flow and therefore stall the wing for less downforce and drag. This would give an extra boost on the speed of the car.
Another noticeable detail is that both Lotus and Mercedes now have an extra small outlet below the rear wing. This is used to let out leaked air under the rear wing when the upper outlet is not supposed to be switched on.
In the last few races, Red Bull came back to the dominate position again nearly as the situation in previous 2 seasons. It’s not due to a development of one single miracle part, but rather the whole aerodynamics pakage – DDRS, Flexi front wing and nosecone, modifidied exhaust profile etc. I’ll look into the DDRS first in this post and hopefully continue this series in coming posts.
After Mercedes’ Front wing DDRS and Lotus’ passive DRD, Red bull’s introduced their DDRS, kind of inspired by both systems. As the name DDRS suggests, it’s activated by DRS, the same as the Mercedes system. However, it’s fully equiped in the rear wing assembly same as the Lotus system.
RB8 now has a small hole on each side of the endplates, which is covered by a oversized plate attached to the rear wing main plane when DRS is not activated. When DRS is in operation, the rear wing tilts and exposes the holes, allowing air to pass through and guided out underneath the beam wing to stall it.
Red Bull DDRS inlet – notice the hole exposed as the covering plate tilts
As mentioned, Red Bull’s DDRS is fully compact in the rear wing assembly. The duct curve is slightly shown in some close shots on their endplates.
Red Bull DDRS – Duct curve on endplates?
There’s possibly two outlets under the beam wing – one in the middle and the other near trailing edge, although the exact part it stalls – either the centre of beam wing or wing tips – is still ambiguous. ScarbsF1 inclines to the wing tip stall idea as he sees small impact on stalling the middle section (Analysis: Red Bull DDRS). Major media however believe that it’s the centre part that stalls although there’s no clear picture showing the existence of these holes. techF1Les came up with three posible conficurations with the last one mostly proved by actual observation.
Red Bull DDRS possible outlets position
I personally agrees with the wing tip stall argument since I’ve not noticed any clear picture showing the central part outlets. Some arguments regarding the central part stall working in coherence with diffuser does look interesting, although more evidence is needed for that.
I was a bit surprised as Red Bull introduced this system near the end of the season, while it’s going to be banned next year. However, they’ve somehow showed it’s worth investigating by continuing strong performance recently. This system has definitely given Red Bull a better qualifying performance and top speed boost during the race.
There’re quite a few comprehensive analysis on Lotus E20 Drag Reduction Device, however I’m trying here to put on a simple explanation to the system so that everyone can understand.
Lotus DRD, we call it DRD instead of DDRS as this system is nothing related to DRS, although the function is the same – reducing drag. It’s completely passively controlled by car speed to achieve drag reduction. The benefit of isolating from DRS (compared to the Mercedes DDRS system) is that it’s not limited use to the specific DRS area on the circuits and does not have a delay over activation – the Mercedes DDRS needs to go all the way from the rear wing to the front wing, causing delay.
The whole structure of this device looks like this:
It basically contains two inlets – the airbox and the ‘ears’ and two outlets – the periscope/L duct and the mini diffuser/monkey seat. I’m not going through the internal ducting as it’s purely speculation going into this area, for which I’m not very sure about.
Besides the normal airbox inlet, Lotus places two additional inlets along each side of it like two ears. Those ears help directing excess flow into the rear part, thus reducing turbulence from air spillage and help generating more downforce when DRD is not activated. In addition, it’s suspected that the air that goes into the ears and airbox subsequently flows into different route through internal ducting to the rear outlets. However, as I’ve mentioned, I’m not going into detail on this.
Airbox and ‘Ears’ On Lotus E20 Airbox
There are two ways that the air can goes out of the car, either through the mini diffuser or the L duct. The path that the air goes depends on the speed, or air pressure.In a relatively low speed, i.e. off throttle condition, air mainly goes through the mini diffuser since higher pressure is required to push air through the narrow L duct. As the critical speed reaches, air can pass into the L duct then exit through 2 slots on each side of the duct, causing stall on the main plain of rear wing.
The structure of both the mini diffuser and the L duct is quite tricky if you look into the detail.
For the mini diffuser, there’s actually a small internal part inside which aids downforce generation when device is not activated.
Lotus E20 Mini Diffuser/ Monkey Seat Detail
The L duct is very narrow to ensure that it’s only activated when a certain speed is reached, those tiny air exiting slots make huge difference to the airflow pattern – cause flow separation to stall the wing. The FlowViz picture can clearly show this effect:
Lotus E20 Flow Viz Interpretation
Basically Flow Visualization paint is a special liquid sprayed to the car in order to study airflow on the surface. When the car runs, flow pattern is recorded as the paint redistribute due to the air goes over. So as can be seen in the Lotus Flow Viz illustration, there’s a V-shape pattern beneath the main rear plain right in the middle at the exit of the L duct, indicating flow separation, i.e. drag reduction. Also those 3-5 cm slots are shown clearly once zooming in to this area:
Lotus E20 L duct/ Periscope Slots Detail
The device need to be adjusted from race to race to modify the speed of activation, mainly by modifying the cross section of the mini diffuser and the L duct.
So as Mercedes came up with the intelligent DDRS which is activated by DRS, Lotus brought out a entirely passive system DRD. However, neither of the systems has given distinctive advantage to their cars. Regardless of that, it’s still a very clever idea that may inspire engineers for more innovation.
F1 is finally back this weekend to Spa, a favourite circuit to many F1 fans and drivers. Lots of curiosity and excitement arised over the cars’ upgrades after the summer break. It is expected that McLaren would use their new DDRS design in Spa, together with Lotus further exploring their DDRS after the last two races before summer break. So huge focus is on DDRS again, which was introduced by Mercedes at the beginning of the season…
Let’s have a look at DRS first. DRS stands for Drag Reduction System. It was introduced to F1 in 2011 season, basically referring to adjustable flap on the rear wing. It’s a fairly simple system, as clearly illustrated in this 2011 video from Red Bull on both KERS and DRS. Jump to 1:24 for the DRS part.
KERS and DRS explanation
So when DRS is activated, the flap on the rear wing get flattened and therefore opens a slot at the rear wing, which produces a better streamlined shape of the car and consequently reduces both the downforce and the drag. Note that with the reduction of drag always comes along the sacrifice of downforce although the degree of reduction can be different. However, at long straights, less downforce is needed. By activating DRS, the car can boost 10 to 15 km/h extra top speed. DRS is allowed all the way in qualifying, but in races, only through overtaking zone when the a car is within 1 second to the front car after 2 laps is finished.
As the words suggests, DDRS = DRS+DRS, a double drag reduction system. It was primarily developed by Mercedes, as one of the biggest innovations of 2012 season. In addition to the DRS system, Mercedes introduced a passive system which activates when DRS is open. It basically feeds the air from the rear wing and guide it through the cockpit to the front wing, therefore forms another DRS at the front part of the car.
Construction of Mercedes DDRS
The video below shows clearly how the air flows through the car:
Mercedes DDRS System
DDRS is very good for further reduction of drag on the straights, it more importantly gives the car good aero balance. In F1, aero balance is very important to guarantee stability – the ratio of downforce produced on the front and rear wing should be roughly the same as the car front and rear weight distribution. DRS is normally used on straights as it would be dangerous to use at corners with an unbalanced car, whereas DDRS has a potential to be used in less curved corners, also allowing the driver to activate it earlier after corners before going onto straights.
How does Mercedes DDRS work? – History and Analysis
We might need to go through some history here. It’s widely acknowledged that the design of DDRS is inspired by the F duct of McLaren in 2010, which is a great application of passive ducting system fighting against those rules set by FIA.
A bit off topic.. if you look through the innovations in f1 technology history, what engineers have been doing can be summarised as ‘finding the flaws of F1 rules’! 2009, double diffuser; 2010, F duct; 2011, exhaust blown diffuser – all banned after one season of usage. However, the idea of passive ducting system has been inspiring engineers since 2008, being modified every year based on the rules.
For your information on F duct, as a genesis of DDRS:
How does F duct work
So the experience from F ducts tells us:
Slots on the wing can be used to disturb air flow, therefore stall the wing to reduce drag (Note: stall of F1 wings means a reduction of downforce and drag rather than lose of all lift force on airplane wings)
It’s beneficial ducting the air
Passive system is a clever choice to gain downforce/ reduce drag without violating the rule
These are taken into Mercedes DDRS design, in which the air is guided from the rear wing through the channel along the car, exit at the front and cause front wing stall – A clever passive system which only operates when DRS is activated.
Question still exists on how the air flows exactly out of the slots. Generally speaking, engineers add slots to the wing either to generate more downforce or to reduce drag depending on the direction of the slot. In this case, we’re focusing on reducing drag, in which the direction of air flow should disturb natural flow, causing flow separation in order to stall the wing.
It’s suspected that besides the F duct idea, Mercedes DDRS is also related to their W duct design in 2011 on their front wing, which guide the air into the nose and feed it into different parts of the front wing
W duct of Mercedes W02 in 2011
The point here is that by blowing air underneath the front wing, you’d be able to increase the maximum angle of attack allowed for the car to run. Basically engineers increase the angle of attack to increase downforce until a critical angle of attack is reached, in which case the wing stalls and no more downforce can be generated. The blown air has a positive effect on increasing this angle, therefore allow higher downforce to be generated. So the slot here in W duct aims to increase downforce. It’s uncertain whether this now works along with Mercedes DDRS system so that more downforce is generated when DRS is inactive while stall occurs when DRS is active – considering aero balance, there is actually not too much downforce required on the front wing. Nevertheless, opening slots on the front wing could be an inspiration for Mercedes when developing their DDRS this year.
However, the use of DDRS system didn’t make Mercedes the fastest car in F1. It seems to work well in qualifying while not showing any benefit in Sunday races. The effect of stalling the front wing is quite controversial, even though the advantage of aero balance, top speed increase and passive activation still looks really appealing.
Lotus Passive Pylon Duct
After Mercedes, Lotus brought out a completely different DDRS design that instead of reducing drag at the front wing, it further reduces drag at the rear. Since FIA has clearly banned F duct design that uses slots at rear wing, Lotus places the slot at the connection between the rear wing and the engine. This would also cause wing stall and is passively activated by DRS beyond a certain air speed. As this system is only tested in the last two races, no consensus is reached yet on how it works exactly. However I’ll keep updates on this system.
I’m very curious on what kind of DDRS system McLaren is going to use. It’s expected and should be completely different from the Mercedes and Lotus systems. DDRS system, especially Mercedes one, is actually very difficult to copy since it requires the change of whole monocoque. Like all the previous innovations, DDRS is likely to be banned in 2013 F1 season although the official announcement has not come out yet. Let’s see what can happen to DDRS in the rest of 2012.
Spa is in fact one of the most ideal circuit for DRS application – capable of reducing lap time by 1.2s! So get excited for the race this weekend!