Why does pressure build up in fenders? 1

[Pcar928]

I have heard only very basic arguments as to why. I want to know what interaction does the tire have on the air stream to cause a high pressure in the fender? Is it really the tires fault or simply the fact that the fender is generaly open and traps air in the fender at a high pressure? How does this work?

 

[TheBlacksmith]

If you don't have tires on the car it proabably won't go fast enough to build up much pressure so I guess there is a correlation.

 

[IRstuff]

What pressure build-up?

TTFN

FAQ731-376

 

[Pcar928]

Inside the wheel well, under the fenders is a high pressure zone when the car is moving foreward. Both front and rear have this issue, a lot of the times in racing and sports cars you see louvers or vents or just an open fender to thwart pressure buildup. It creates lift and in general is unwanted.

 

[GregLocock]

Buy 'race car aerodynamics' by Katz.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[HRHtex]

Are you sure it's a high pressure area? With the BMC Mini family of cars the the air flow from the radiator was into the front well as they had discovered that it was actually a low pressure area - not high.

 

[IRstuff]

You are jumping to conclusions. A vent usually means someone wants airflow, PERIOD, not necesarily anything to do with pressure.

TTFN

FAQ731-376

 

[patprimmer]

Or they think vents look sporty or sexy.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[MacGyverS2000]

I vent my wheel wells to get some fast-moving air to the brake rotors... but then again I am just a stupid sparky...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Tmoose]

I think Jim Hall has said he used fender vents to reduce lift resulting from "pressure buildup." on early Chapparals.
It wasn't too many years before he'd re-thought the large radius rocker panels, so I guess the early aero must be considered pretty rudimentary/elementary. nonetheless That 2C sure looks like a race car to me.

http://www.v-8.ch/Exoto/Chaparral 2C/Chaparral 2C History.htm

======================================

http://www.motorsportcollector.com/071502Images/Exoto/ChaparralL.jpeg

http://t3.gstatic.com/images?q=tbn:...haparral/Chaparral_2_Aa_front_quarter.jpg&t=1

http://www.thechaparralfiles.com/img/Chaparral cars/2A with Jim Hall.jpg

Dan T

 

[tbuelna]

pcar928,

One reason is that the airflows around the fender and underbody ahead of the wheel well tends to be of higher velocity and lower pressure. So when it dumps into the larger (diffusing) volume created by the wheel well, the airflow naturally loses velocity and locally increases in pressure.

To mitigate this situation, closed wheel race car bodywork use spoiler lips at the front edge of the wheel opening, fender louvers above the wheel well, and extractor ducts behind the wheel well. All of these devices serve to create a zone of reduced airflow pressure within the wheel well volume.

Regards,
Terry