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10 Oct 2012

Since the start of the season McLaren have lead the way with their exhaust idea, with most of the field converging on a similar solution.  The 'Coanda' Exhaust as it has been coined uses the Coanda effect to draw airflow into the important 'Coke Bottle Region' situated above the floor of the car.  This helps to speed up the process of the diffuser resulting in more rear end downforce.

The 'Coanda effect' is an aerodynamic effect named after the pioneering aerodynamicist Henri Coanda.  Henri realised that by introducing a jet stream (in our case the exhaust plume) nearby airflow is attracted to the neighboring surfaces.

McLaren realised this and their original and newer iteration (introduced in Hockenheim) both use the principle in order to manipulate/guide the airflow over the diffuser.  In McLaren's newer iteration pictured below the team added shark gills aft of the exhaust to further influence the behavior of the airflow toward the Coke Bottle Region.

As teams have further understood how to use the 'Coanda Effect' to their advantage they have changed the profiles of their sidepods forward of the exhaust outlet in order to further draw more air around and over the sidepod towards the Coke Bottle Region.  Most of the teams with the 'Coanda' Exhaust have Vortex Genorator's atop of the Sidepods in order to speed up the airflow and reduce the boundary layer toward the exhaust channel.  The exception being McLaren & Sauber who have Sidepod Wings.

Above: McLaren's Original Vortex Generators were supplemented with a 3rd VG before they moved to the Sauber style 'Wing' arrangement (Below)
Above: McLaren's Sidepod Wings as used in Suzuka

The last 2 larger teams left without the 'Coanda' Exhaust were Mercedes and Lotus, with Mercedes testing it in Magny Cours and implementing it since Singapore the Lotus team who have had such a design the back burner have now announced they'll bring theirs to Korea. 

The Lotus E20's design ethos has very much been centered around great internal aerodynamics and so with Lotus introducing the 'Coanda' exhaust we should see a remarkably refined package introduced in Korea.  It will require upgrades to the frontal portion of the sidepod along with the downwash section of the sidepod being resculpted, a new floor, diffuser and maybe even a repositioning/re-design of the beam wing.  Mercedes neglected to implement such radical changes to the WO3 when they introduced theirs in Singapore and this could be part of the reason they are still struggling to get the performance leap from it they expected.  Both Lotus & Mercedes opted to stay away from the 'Coanda' Exhaust until such point they fully understood the concept in CFD and the Wind Tunnel knowing that implementing it in haste could be time and resources wasted.  With Focus now switching to 2013 designs having time on track with this exhaust system could prove crucial to next years campaign.

Lotus are also eyeing 4th place and now only need 24 points to overhaul Ferrari, this would not only be a substantial scalp in sporting terms but would provide the Genii Capital owned team with a significant financial boost from FOM prize money.

Ferrari have also stated they were looking to bring a large upgrade package to Korea and so with exhaust manipulation invariably offering the largest gain they too may look to further enhance their exhaust package.  Ferrari already have their own interpretation of the 'Coanda' exhaust however like Sauber did in Singapore they may revert to a more ramped style exhaust to gain performance as both these teams have their radiators in the vertical position.  Red Bull albeit with their tunnel system also run a more downwash ramp design than the 'Coanda' exhaust of McLaren etc.

EDIT 11/10/12

Thanks to Sutton Images here are the first images showing the 'Coanda' style exhaust on the Lotus E20

Above: Rearward shot of the E20 sporting two different configurations (But still in build up) you can see the new 'Coanda' exhaust on the right along with some shark gills aft of that on the engine cover. On the left the exhaust cover hasn't been placed but the arrangement looks similar to their higher mounted exhaust. Also worth noting from this picture is the DRD engine cover has been flown out so could still feature in their test plans. On the left Rear Wing Endplate we can see the 3 flow conditioners added to influence the airflow (These have been tested in previous GP's)

Above: More Neutral design in the 'Coanda' position as alluded to in the description above on the left hand sidepod

Above: Image of the floor changes in order to further use the influence of the new exhaust package


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