I know this is not an F1 related question, but you lot seem to be the most knowledgable on the web when it comes to all things motor racing. As part of my uni degree as part of the aerodynamics course, we have been set a coursework to take an ordinary saloon, in our case an Alfa Romeo 155, and improve its aerodynamic performance. We are taking the route of an all out racer a la DTM 96, but i have a question. On these cars does the rear wing drive the diffusor at all? these cars had full ground effects but the rear wings were mounted some height above the diffusor exit. i would have thought that some effect would have been felt. Also did these wings serve any other purpose, as from reading books, this rear deck seems to be somewhat turbulent and any aero appendages seem to cause more disturbance causing a decrease in lift. Any ideas would be gratefully appreciated. thanks
Aerodynamics
Started by
Kid Prozac
, Feb 05 2002 21:31
1 reply to this topic
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#2
Toby Padfield
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- 15 posts
- Joined: February 02
New Member
Posted 06 February 2002 - 18:51
KP,
The extent of interaction between the rear wing of a road car (saloon/sedan/etc.) and the diffuser is minimal, as the vertical distance separating the two is quite large (in automotive aerodynamics terms). Notice how close the lower wing elements on either Formula-type cars or Sports Prototypes are to the diffuser in order to create the "driving" effect. The main purpose of decklid-mounted rear spoilers on sedans/saloons is to provide some amount of downforce. The air flow in the area aft of the greenhouse typically becomes detached/separated, promoting lift on the rear axle. Adding the wing delays/prevents this, which reduces lift, and usually (for race cars at least) produces some amount of downforce, depending on how high above the decklid it extends.
There are several resources I would recommend you check out with respect to this project. Race Car Aerodynamics: Designing for Speed by Joseph Katz is a good general reference, with some stuff on road cars and Sports Prototypes, in addition to Formula-type cars. Second, the magazine Racecar Engineering has featured several articles over the years on DTM and Touring cars, with specific details on aerodynamics. Lastly, there are at least two SAE Technical papers that discuss aerodynamics and DTM/Touring Cars. One was written by some guys from Opel in 1998 I believe, but I don't have it in front of me to know for sure. The other is 1999-01-0647, The Role of the Moving Ground for Automotive Wind Tunnel Testing on Race Cars, authored in part by Sergio Limone, who was actively involved in the Alfa DTM project, and more recently the 156 Super Touring project, which is described in the paper. I can provide you with specific issues of RE and the other SAE Paper number is you would like. If it is ok with the moderator, Desmo, I can have the 1999 paper placed on the forum bookshelf, or whatever he is calling it. Best of luck on your project.
T...
The extent of interaction between the rear wing of a road car (saloon/sedan/etc.) and the diffuser is minimal, as the vertical distance separating the two is quite large (in automotive aerodynamics terms). Notice how close the lower wing elements on either Formula-type cars or Sports Prototypes are to the diffuser in order to create the "driving" effect. The main purpose of decklid-mounted rear spoilers on sedans/saloons is to provide some amount of downforce. The air flow in the area aft of the greenhouse typically becomes detached/separated, promoting lift on the rear axle. Adding the wing delays/prevents this, which reduces lift, and usually (for race cars at least) produces some amount of downforce, depending on how high above the decklid it extends.
There are several resources I would recommend you check out with respect to this project. Race Car Aerodynamics: Designing for Speed by Joseph Katz is a good general reference, with some stuff on road cars and Sports Prototypes, in addition to Formula-type cars. Second, the magazine Racecar Engineering has featured several articles over the years on DTM and Touring cars, with specific details on aerodynamics. Lastly, there are at least two SAE Technical papers that discuss aerodynamics and DTM/Touring Cars. One was written by some guys from Opel in 1998 I believe, but I don't have it in front of me to know for sure. The other is 1999-01-0647, The Role of the Moving Ground for Automotive Wind Tunnel Testing on Race Cars, authored in part by Sergio Limone, who was actively involved in the Alfa DTM project, and more recently the 156 Super Touring project, which is described in the paper. I can provide you with specific issues of RE and the other SAE Paper number is you would like. If it is ok with the moderator, Desmo, I can have the 1999 paper placed on the forum bookshelf, or whatever he is calling it. Best of luck on your project.
T...
