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.
After going through two low downforce cicuits Monza and Spa, F1 came to Singapore, a narrow street circuit requiring high downforce. Correspondingly, most teams brought new setup for this track, while some of them gives a speed boost, others don’t seem to benefit anything. Successful examples are Red bull’s new break ducts and Mercedes Coanda effect exhausts. However Ferrari, using Alonso’s word, had a development error again, while Lotus expierenced a lack of grip throughout the weekend.
They’ve finally joined the group of ‘Coanda’ Exhaust after it was introduced by McLaren early season and used by Ferrari, Sauber, etc. The new exhaust utilise sidepod bulges to improve airflow passing through the sides of the car to the floor. Coanda effect basically describe the tendency of fluid attaching to the nearby surface. The bulge would help bending the flow at exhaust area down to the diffuser, therefore seal and speed up the airflow to create a low pressure area underneath the car. This effect increases downforce at the rear and gives advantage at low speed corners – that’s why it’s preferred in Singapore.
Mercedes Coanda Exhaust
The narrow street circuit indicates huge pressure on the brakes and cooling system. Red Bull came with new brake discs and ducts made of CER, a new material whose wear resistance feature is about 4 times better than the old CCR.
Red Bull Singapore Front Brake Duct Detail
They’ve also modified their front wing with slots in the front of wheel area to reduce wake behind and seperate flaps to decrease drag induced by the high downforce setup.
Red Bull Singapore Front WIng
Williams was in quite good pace in Singapore actually with Maldonaldo hitting 2nd in qualifying, although hydraulic problem for Maldonaldo and KERS problem for Senna leave both drivers nothing in this race. They’ve introduced a much more rounded nosecone with centre bulge in this race, quite similar to the Lotus one.
Williams Singapore Nosecone
They brought two sets of wings into Singapore with the new one having more louvres on the endplates and deeper cuts on the top flap. There’s also 8 gills added to the side of the diffuser, wishing to generate more downforce. However, testing result on Friday was rather frustrating so that the team decided to use the oler version for Singapore race. This happened quite a few time throughout the season, which makes Alonso quite worried – Ferrari focused on understanding ‘development errors’
Ferrari Singapore Rear Wing – Not Used
They’ve modified their rear wing for Singapore and here is a nice flow viz picture of it.
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!