Rear Diffusser Design For Race Car? 1

[Spice52]

Hello

Can anyone answer this please?

I need to manufacture a rear diffusser for a Supercar/Race Car.

In plan view does the trailing edge of the diffusser need to be straight, or can it be curved?

Many thanks

Marcus

 

[rb1957]

i think most race car rears are bluff ("straight") to minimise buffet, ie to provide a fixed point of separation. i think you could do a little bit of tapering, to reduce to end area. i think, from looking at F1 cars as an example, that much of the design work involves introducing the flow from under the car into the flow behind the car.

good luck

 

[Dave K]

If its going to be used on a racecar, check the rule set for whatever series you're running. Some have specifics regarding the diffuser shape.

-Dave
Everything should be designed as simple as possible, but not simpler.

 

[Spice52]

Thanks lots all

Something else you all may be-able to shed some light on:

If the diffuser angle is too steep, does the air stall?

What do you think is the max angle?

Thanks for the help

Marcus

 

[Dave K]

General "rule of thumb" is 7deg, but I know teams that have run as high as 11deg. I did one that was going to be very short, so I made the angle 11deg, but on a revision we made it longer (starting at the rear axle line), and sloping at 7deg, and it worked alot better.

I think too much angle causes seperation and turbulance, which kills the efficientcy. The number of strakes will make a difference too. My understanding is they help clean up the turbulant air from the rear tires. I've noticed the C6R's, running alot more strakes in the diffuser, and Prodrive always seemed to use alot.

-Dave
Everything should be designed as simple as possible, but not simpler.

 

[wes616]

There was a good article in Racecar Engineering[/b] (Magazine) last spring regarding some work that the University Of Missouri - Rolla did with their Formula SAE car. I don't have a link, but I remember reading it. If you can, check it out. They did a lot of wind tunnel testing at Ford or GM, with their car.

Good luck,

Wes C.

 

[Dave K]

I believe that was the Sept. 2004 issue.

-Dave
Everything should be designed as simple as possible, but not simpler.

 

[sprintcar]

If your wing section has a recognized profile, you can find the stall angle in the database.
Hanley has a couple design programs for wings - check his website.

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