Sunday, October 14, 2012

Red Bull DDRS Plausible Functionality

Red Bull had introduced their own version of the Double DRS system (DDRS) system in Singapore, tested it and used it for the race although at the time no one outside the F1 teams realised it. In Japan though thanks to Sutton Images, we had seen photos of the RB8 with the DRS open revealing two holes in the endplates, one in each side. At that point we knew that Red Bull were using a DDRS system but we didn’t know what they were blowing. We were sure though that unlike Mercedes Red Bull weren’t blowing the front wing as photos of the front bulkhead showed that it was unchanged.
The aim of this article is to reveal a possibly or definitely what Red Bull is blowing with their version of the DDRS. The first thing discovered this weekend in Korea, again thanks to Sutton Images, is that each hole is actually divided into two smaller ones, however not of equal size. 

Then the idea rose that they were actually blowing at two different places. The first one is possibly below the rear wing main plane in order to stall flow in the corner between the rear wing main plane and the endplate to reduce downforce and increase top speed. 

Furthermore the size of the hole below the rear wing main plane is consistent with the size of the smaller hole in the endplate. 

Here we come to the most intriguing part, it is believed by other Formula 1 technical journalists, Giorgio Piola and Mark Hughes, that Red Bull is blowing the central 15 cm of the beam, where there are less restriction as to what teams can do, in order to reduce its downforce and achieve the drag reduction effect.

However, the central 15 cm of the beam wing is situated behind the gear box, the engine and Red Bull’s cannon like hot air outlet, so it doesn’t get clean flow and is producing relatively less downforce already. So the drag reduction effect would be that high. At first I though that it couldn’t be right, they must be blowing something else. But then it dawned on me.  To understand why they are blowing the central 15 cm of the beam wing we have to look at Red Bull’s ramp coanda exhaust with the tunnel underneath. Red Bull unlike other teams is using a ramp to guide the exhaust to the diffuser instead of a McLaren style bulge. By doing this they can more accurately aim the exhaust plume to the diffuser (red colored flow). The ramp though takes up space from the tight coke bottle shaped sidepods that Andrian Newey’s cars have been featuring since 2009. The effect of the tight coke bottle shape was cleaner flow on top of the diffuser allowing it to produce more downforce. In order to retain this advantage Newey has created two holes underneath the coanda ramp. 

The first and bigger tunnel (blue colored flow) is directing air flow inside the sidepods and together with the sidepods internal flow, the air exits above the diffuser again to gain the advantage described above. The second and smaller tunnel (yellow colored flow) is redirecting flow to the starter motor hole, something that Red Bull was doing last year with the RB7 as well. The two tunnels however add a lot of surface area to the bodywork and create additional drag and the RB8 had one of the lowest top speeds.

The reason for blowing the starter motor hole is because it is the steepest part of the diffuser and the one most difficult to keep the flow attached to. The started motor hole behaves like an extra slot in a wing. Blowing inside that slot accentuates this effect keeping the flow attached.

So what does all this have to do with the DDRS system? 
The low pressure below the beam wing helps with the extraction of air from the bigger tunnel and from the diffuser. Stalling the central section of the beam wing, removes that effect and airflow from inside the tunnel is now slower and flow underneath the central 15 cm of the diffuser is more likely to stall. When the air entering the two tunnels underneath the coanda ramp can not flow easily on the other side it will spill out and follow the rest of the airflow to the rear of the car. 

This sheds some of the drag induced by the two tunnels. So Red Bull are getting a triple effect by blowing the central 15 cm of the beam wing by removing drag from the beam wing itself, stalling the central 15 cm of the diffuser and shedding some drag from the two tunnels underneath the coanda ramp. Add to that the drag reduction from blowing some air below the rear wing main plane and they have achieved a quadruple effect.

If this is indeed what Red Bull are doing, it’s ones again hats off to Andrian Newey and Peter Prodromou.

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