Diffuser (motorsport)

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Red hatched area = effective areas of the diffuser

In motorsport, a diffuser is the active surface in the underbody area of ​​a racing car to improve aerodynamics through a suction effect. With its asymmetrical shape, the diffuser ensures pressure distribution under the underbody and thus downforce .

Mode of action

Measurements show that a small area of ​​reduced air pressure occurs at the transition from the horizontal floor to the diffuser while driving . Air flows from both sides under the vehicle and forms vortices in pairs , which flow through the diffuser in opposite rotation .

Diffusers are the least understood areas of racing cars and were the subject of many experiments the aerodynamics until at least their effect chain was measured and recorded. Early evidence of downforce appeared around 1980, but details of the flow did not become known until two decades later. The air entering from the side and the rotation it triggers is the main cause of the effect. This is in contrast to other designs with floor effect that go back to the Lotus 78 and seek to minimize side air exchange. Under such conditions, a diffuser largely loses the desired effect and, on the other hand, gains when the tail units in the front area of ​​the vehicle introduce the eddies. The maximum angle of inclination of a diffuser is around 15 °, otherwise a flow stall occurs and its effect is prevented. The optimal diffuser length is half the vehicle length.

Front diffuser

With the front diffuser, baffles under the front spoiler direct the airflow upwards behind the front wheel arches. Applications can be found in prototypes and Group CN vehicles.

Rear diffuser in Formula 1

McLaren MP4 / 4 with early diffuser in Formula 1

In Formula 1 , the use of a diffuser is subject to FIA technical restrictions . The diffuser makes it harder for vehicles following behind to use the slipstream . Up until the rule change in 2009, the diffuser accounted for up to 70 percent of  the total downforce of the Formula 1 racing car - with a share of 10 percent of the total aerodynamic drag . It causes air turbulence in the following vehicles, which reduces the contact pressure . In order to reduce the turbulence behind the car caused by the diffusers and thus to facilitate driving in the slipstream and thus also overtaking, the FIA ​​adapted the specifications for the underbody for the 2009 Formula 1 World Championship . Article 3.12.7 of the official technical regulations now states: "No body element visible under the car that is up to 350 mm behind the rear axle line may be higher than 175 mm." With this change, the previous diffusers in their design and thus their effect was curtailed, the share of the total downforce was then still around 40 percent.

Double diffuser of a Brawn BGP 001 (2009)

Double diffuser

The so-called double diffuser, first installed in the Formula 1 racing cars from Brawn GP ( Brawn BGP 001 ), Williams ( Williams FW31 ) and Toyota ( Toyota TF109 ) in the 2009 season, increased the contact pressure by a second, shorter plate above the actual diffuser. The double diffuser of the Brawn BGP 001 also had a central channel that was not visible from below, which, compared to simple diffusers, produced higher downforce and thus more traction.

The possibility of such a rule design existed before, but only brought a real advantage with the rule change in 2009 to reduce the size of the diffusers. When the advantages of the three teams equipped with double diffusers became clear in the winter tests before the 2009 season, the discussion about their legality began. The Ferrari , BMW Sauber , Renault and Red Bull teams protested against the built-in double diffusers before the first race in Australia . The responsible race stewards rejected the protest and declared the diffusers to be compliant with the rules. The protesting teams appealed this decision, but the FIA ​​Court of Appeal endorsed the stewards' decision of April 15, 2009, declaring the double diffusers legal in the last resort. At the Chinese Grand Prix , a few days after the decision of the FIA, McLaren and Renault started with modified diffusers, the remaining teams followed suit with new developments. Back in March 2008, Ross Brawn , then team boss of Honda F1, suggested making the diffuser regulations simpler and more precise. For the 2011 Formula 1 World Championship , the double diffuser was banned.

Triple diffuser Toyota TF109

Triple diffuser

In the 2009 season, Toyota developed a triple diffuser from the double diffuser on its Toyota TF109 model .

Blown diffuser

For the 2010 Formula 1 World Championship , Red Bull Racing invented the "blown diffuser". In the Red Bull RB6 racing car , the hot exhaust gases were directed onto the diffuser roof.

gallery

Web links

Commons : Diffuser (Motorsport)  - Collection of images, videos and audio files

Individual evidence

  1. ^ A b c Joseph Katz: Aerodynamics of Race Cars . In: Annual Review of Fluid Mechanics . Volume 38. Annual Reviews , January 2006, pp. 27-63 .
  2. ↑ a b Joseph Katz: Race-car aerodynamics (PDF; 187 kB) McGraw-Hill . Pp. 4-5. Archived from the original on February 3, 2016. Retrieved January 16, 2013.
  3. ^ A b c Xin Zhang, Willem Toet, Jonathan Zerihan: Ground Effect Aerodynamics of Race Cars . In: Applied Mechanics Reviews . Volume 59. American Society of Mechanical Engineers , Jan 2006, pp. 40–42 ( PDF 1.24 MB online [accessed January 16, 2013]).
  4. ↑ Michael Trzesniowski: racing car technology . 2nd Edition. Vieweg + Teubner, Wiesbaden 2010, ISBN 978-3-8348-0857-8 , pp. 128 .
  5. ↑ Official technical regulations of the FIA ​​from March 17, 2009 (English; PDF; 833 kB)
  6. ↑ Michael Trzesniowski: racing car technology . 2nd Edition. S. 156 .
  7. ↑ formula1.com Brawn BGP001, diffuser layout
  8. ^ Motorsport-Total - Internet site: Der Insider: Diffusoren, KERS, Espionage und Co. Archived from the original on April 15, 2009 ; Retrieved December 7, 2012 .
  9. ↑ "Protest against diffusers rejected!" - motorsport-total.com on March 26, 2009
  10. ↑ "FIA decides: Diffusers are legal!" - motorsport-total.com on April 15, 2009
  11. ↑ "Brawn:" Now you are interested "" - motorsport-total.com on April 5, 2009
  12. ↑ formula1.com of November 30, 2010 Farewell to F-ducts and double diffusers
  13. ↑ formula1.com Toyota TF109 - 'triple-deck' diffuser, accessed February 2, 2011
  14. ↑ Auto Motor und Sport Extra: Edition 26/2010. Technology innovations 2010: Air number. Page 16 ff
  15. ↑ formula1.com of March 13, 2010 Red Bull RB6 - new exhaust positioning