NYTimes Aero Article - Edgy, Yet Still Aerodynamic

[instarx]

Nice article in the New York Times today about aero designs and where car-makers are heading with edge design. Several interesting pictures.

http://www.nytimes.com/2008/12/21/au...es/21AERO.html

Most interesting quote: "Aero remains a black art."

[basjoos]

These "aeroedges" appear to be mostly bandaids to compensate for aerodynamic inefficiencies downstream from them. For example, the aeroedge that deflects the air flow on the side of the car outwards to reduce turbulence around the front wheel housing. This increases the effective frontal area, but reduces the turbulence created by the front wheel opening. A lower drag solution would be a a rounded front combined with a front wheel skirt, but the aeroedge allows them to style a "normal" looking car with slightly less drag than the normal looking car would have had. In this application, the aeroedge is acting as an airdam for the side of the car. It diverts the airflow away from an aerodynamically dirty portion of the car, but at the expense of adding additional drag. But if the drag reduction from the area that it is protecting is greater than the drag increase from the aeroedge, then it is a net reduction in drag. But still not as low drag as having a properly designed clean (wheel well skirted) curve running down the side of the car. The edges at the rear of the car are there to clean up the airflow as it leaves the back of the car to reduce the size of the recirculation eddy. But they are still much higher drag than a boattail with practically no recirculation eddy. So these are just bandaids to allow them to build slightly lower drag versions of "normal" looking cars. However these tricks won't get them anywhere near a Cd in the 0.1's.

[instarx]

True, but most people aren't going to buy a car with a boat-tail or wheel skirts on the front wheels. In such a perfect world all our houses would be spherical and we would enter them through hatches. Same with cars - convenience and appearance play a part, too.

With all the discussions here on topics like the advantages/disadvantages of air tabs, or ziggy tape on mirrors, or dimpling, I don't find the ideas mentioned in the article to be so useless or outlandish. After all, they're just ideas (presumably with some wind-tunnel verification even). Who knows where they might lead?

I think the important message of that article is that aero-design is such an unknown that it isn't wise to assume that the conventional wisdom is always right.

[trikkonceptz]

If I have learned anything from my time in the auto industry its that they do not like to take risks, even calculated ones. Fortunately there is pressure from all sides coming that will require more efficient means of transportation.

They are starting to realize that there are greater gains in reshaping automobiles than continuing to tweak an antique power supply, the internal combustion engine.

I'm just wondering how long it will be before some of these concept cars start showing up with three wheels, tadpole style?

It's funny, you know they know what their doing, yet they are so slow to leak it out.

[aerohead]

Newspaper editors and journalists can print whatever they like without legal requirements for rebuttal space.And they can snip and paste,using industry spokesperson comments completely out of context.So far, there is no law against it.If mediocre cars are the target for carmakers,then I applaud them! They need to receive a prize! And if the Kamm-Car,at Cd 0.37 is to be the "standard" for aerodynamic excellence,then lets dispense,once and for all,any talk of tails which might lower the Cd to 0.10 and cars with highway fuel economy in the range of 60-100 mpg.Wouldn't want to do it.As far as aerodynamics being a "black-art",I'd be happy to buy each of the carmakers a 26-Watt CFL for their windtunnel crews.Looks to me like aerodynamics has been fully understood since the day of Sir George Cayley in 1800.Newspapers.gotta love 'em!

[TestDrive]

Originally Posted by aerohead

I'd be happy to buy each of the carmakers a 26-Watt CFL for their windtunnel crews.

What does CFL stand for? TIA

[gascort]

CFL = compact fluorescent lightbulb

soon to be replaced by multi-LED arrays since the U.S. outlawed regular incandescent lights...

[instarx]

If aerodynamics has been fully understood since 1800 why all the discussion of dimples, air tabs, ziggy tape, etc in ecomodder? For decades aircraft designers "knew" that there was nothing better than a teardrop shape for a fuselage, but then in the 1980's it was discovered that constricting the fuselage in the wing area was a much more efficient shape. Even the effect of dimples on golf balls wasn't discovered until 1850ish. Winglets on the end of wings to improve economy are a recent discovery. The danger of wingtip vorteces from landing aircraft wan't fully realized until the 70's or 80's. So it seems kind of silly to claim that aerodynamics has been fully understood since 1800.

Why all the resistance to a few new novel ideas being applied to aero in cars. Doesn't every little bit help? Maybe everyone got up on the wrong side of the bed this morning?

[NachtRitter]

Apologies, but I didn't understand what CFLs have to do with aerodynamics?

Also not sure how it follows that CFLs will be replaced by LEDs because incandescents are being phased out in 2014... that sounds like a non-sequitur... ??

[fanamingo]

Originally Posted by NachtRitter

Apologies, but I didn't understand what CFLs have to do with aerodynamics?

It was meant as a joke. The CFL is intended to provide light for windtunnel crews studying an otherwise "black art".