adding air dams to reduce drag

[MightyMirage]

hi everyne, new member and first time poster here.

i read a fair amount before joining up but ive not found a single topic on redirecting air into the hole the car punches thru the air, sucking the car backward.

what i mean is, obviously a negative effect is created by a small suction behind the car, because the car just moved the air out of its way, creating an invisible "parachute" of circulating air, slowing the car down.

now, obviously the first thing to do would be too add aero or whatever modifications can be done too reduce this swirling vortex of gas slurping vacuum, but not everyone can live with a boattail or cam back ect.

has anyone done any real testing on redirecting air from high pressure areas (like wheel openings or under the car) and introducing it directly into the "parachute" of drag, effectively relieving the "suction", and increasing the airs ability to simply flow off the cars roof line or trunk?

please keep in mind, I'm new, but ive read a fair amount. maybe this has been thoroughly discussed, but i have not been able to find it mentioned anywhere.

thanks everyone!

[MightyMirage]

.....

[user removed]

Smokey Yunick did it in the 1960's until NASCAR caught it and banned the practice.

Welcome to EM

regards
mech

[elhigh]

Hi,

Don't get crabby nobody has shaken your hand yet. It's Easter Sunday, lots of people are doing stuff...and to be frank, this topic has been addressed at length in the Aerodynamics section.

You're talking about the many many many things people have already talked about or indeed done in general, and the Template in particular. Check it out: http://ecomodder.com/forum/showthrea...ion-21952.html

More than one member has said it before: Your bigger gains are made at the back of the car. They're talking about the vacuum wake and whatever steps might be taken to make it smaller, to make it less intense, etc. It sounds to me like you're looking particularly at the "less intense" part, of reducing the depth of the vacuum behind the car.

Am I reading you rightly so far?

[mcrews]

As he said, it is EASTER Sunday.
Sure, people cheated and 'read' ecomodder' during their sermon BUT they certainly weren't going to type a response during the sermon.

Have you aired your tires up to 40+psi?

Welcome!

[freebeard]

Welcome. Thanks for lurking.

has anyone done any real testing on redirecting air from high pressure areas (like wheel openings or under the car) and introducing it directly into the "parachute" of drag, effectively relieving the "suction", and increasing the airs ability to simply flow off the cars roof line or trunk?

Yes. aerohead has been at it since 1972.

The wake isn't like a parachute, it's like creeping fingers. Wheel wells are not a good source of high-pressure air, only the stagnation point.

Thanks for putting 'suction' in quotes. Air has simultaneously a pressure and a velocity.

[aerohead]

Originally Posted by MightyMirage

hi everyne, new member and first time poster here.

i read a fair amount before joining up but ive not found a single topic on redirecting air into the hole the car punches thru the air, sucking the car backward.

what i mean is, obviously a negative effect is created by a small suction behind the car, because the car just moved the air out of its way, creating an invisible "parachute" of circulating air, slowing the car down.

now, obviously the first thing to do would be too add aero or whatever modifications can be done too reduce this swirling vortex of gas slurping vacuum, but not everyone can live with a boattail or cam back ect.

has anyone done any real testing on redirecting air from high pressure areas (like wheel openings or under the car) and introducing it directly into the "parachute" of drag, effectively relieving the "suction", and increasing the airs ability to simply flow off the cars roof line or trunk?

please keep in mind, I'm new, but ive read a fair amount. maybe this has been thoroughly discussed, but i have not been able to find it mentioned anywhere.

thanks everyone!

*The premise of streamlining is to decelerate the air which the car's body has displaced,without it separating,to reduce,or eliminate the low pressure wake.
*The separation is controlled by a gradual pressure rise,which can only be achieved with a streamlined body (gentle cross-sectional contraction of the body)
Here's an example of a streamlined aft-body

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*If you locally redirect air,anywhere along the body,you cause a local pressure/velocity 'kink' along the flow path which destroys the gentle pressure profile,causing separation downstream,triggering wake formation right there.

*the kinetic energy of the turbulence is lost forever and can never be converted to static pressure which otherwise would dilute the low pressure of the wake.All this leads to high pressure drag,which is what we're trying to streamline away.
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*The 'Kamm back' is based upon the full-boat-tailed streamline body.The length of the car is decided by arbitrary 'practical ' considerations



'Kamm' was aware of length issues,and offered an option of an automatic extensible tail,which would only be deployed on the highway

,something Mercedes-Benz debuted this year with their 'Intelligent Aerodynamic' concept car.