Wheel well fender shape -- aesthetics or aerodynamics?

[berkeman]

I've noticed that many later-model sport sedans and some other vehicles have a new shape for their wheel well fenders. The fenders flare from the car body, and end with a several centimeter flat section before the wheel well. It seems to be a feature across several car brands and models, and seems to be more common in the last few model years.

Does anybody know if there are aerodynamic advantages to this shape, or is it just a style that has caught on? The Tesla below is an example of a vehicle with the flat-section fenders, and the Lexus has the older abrupt style fender shape at the wheel wells...

http://o.aolcdn.com/dims-global/dim...ides/384/812/0/S3848120/slug/l/p4010540-1.jpg

http://o.aolcdn.com/dims-shared/dim...1c1017/203726053/01-2011-lexus-lfa-review.jpg

 

[.Scott]

I think you can count on that change being aesthetic - but remaining aerodynamic.
The most obvious clue that it is not driven aerodynamics alone is that sudden bend along the edge of the flat surface. Nothing aerodynamically optimal would show such sharp curvature along the broad side of a car-size vehicle - or such rapid changes in curvature.

I haven't found a source with a direct statement about how curvature affects drag, but here is one that comes close: http://www.scientific.net/AMM.798.589

The prescribed surface curvature distribution blade design (CIRCLE) method optimises aerofoils and blades by controlling curvature continuity and slope of curvature distribution along their surfaces.

The wheel well is an obvious problem area for aerodynamics. The body design wants to keep a slight vacuum under the car to improve handling and the spinning wheels in contact with the road surface will create turbulence. But once you are out of the immediate area of the wheel well, you would expect smoothly changing curvatures.

 

[Nidum]

Primarily a mechanical design improvement . Gives a stronger edge to the fender and allows the wheels to be set a few mm further apart without increasing body width .