Drag coefficient ??

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Azrich

Well-known member
Joined
Apr 22, 2010
Messages
533
Location
Tucson, AZ
Has Nissan released the LEAF's drag coefficient? The Versa Hatchback's DR is 0.31, so it should be much better than that.
 
According to Nissan's Mark Perry, the Cd is 0.29.

(Forward to 10m30s)

[youtube]http://www.youtube.com/watch?v=pVwtwhvmK0I[/youtube]
 
johnr said:
…Nissan's Mark Perry…

Dude! I was at the D.C. auto show on the second day and there was like nobody there save these two nice ladies keeping an eye on the car. Like I missed Dr. Steven Chu speak, and I missed Mark Perry too? Man! But I do have a couple of nice snaps of the LEAF on my Facebook page. :)
 
LeafHopper said:
Cd was 0.28
johnr said:
Cd is 0.29

Well, like the weight, although I pessimistic in the sense that I'm inclined to believe the 1540 kg mass over the 1300 kg, alas, I do think we have to accept for both the Coefficient of Drag and the Mass that we can but guess. I know they've engineered this puppy well for Drag Resistance (look at it), but drag can only be minimized to a point in a street-legal car. In the end, I'd say go with the more recent number under all circumstances because we can't know for sure what the final '11 LEAF will be like until the first few sales models roll out of assembly.

As a point of reference, the D.C. Auto Show was 10 & 11 March 2010 IIRC, so if the Design Team Member is more recent, I'd be more inclined to go with LeafHopper on this one. Mind you, if they are still tweaking the LEAF -- which is unlikely to be by very much if at all this late in the game -- then the 100 mi on LA4 number could also be off, meaning we know even less about the expected range!
 
Where the air comes back together after being "parted" by an object, it produces a low pressure ("suction") area.

This suction can be minimized by "separating" the smoothly-flowing air from the surface ... just in these "trailing" suction areas.

So, the dimples help separate the air into a turbulent flow behind the ball, which reduces the back-side suction.

On the car, the "spoiler" basically serves the same purpose, creating turbulent flow at the LEAF's rear end.
 
Come on, sailplane guy! We need vortex generators and turbulator tape! ;)

Oh snap - we have vortex generators on the underside, don't we? Woo Hoo!
 
garygid said:
On the car, the "spoiler" basically serves the same purpose, creating turbulent flow at the LEAF's rear end.
On the Leaf, the spoiler is not designed to create turbulent flow - otherwise it'd stick up. It's designed to create a clean edge for air traveling off the roof to separate from, minimizing drag. Look up "Kammback".

Now - the little spoiler on a Civic Hybrid and on many BMW sedans - they are also there to try to keep air attached to the rear window a bit longer by creating a bit of turbulent flow on the hatch, thus reducing the size of the aerodynamic "hole" behind the car and thus reducing drag.
 
garygid said:
The LEAF's spoiler will help create increased turbulance over the sloped back window, etc.
No, it won't make a difference at all. It does not stick up at all, thus does not introduce any turbulence. It simply extends the roof-line a bit. Not to mention that the angle of the rear window is far too steep to cause any significant reduction in wake due to the introduction of turbulence. Look at the vortex generators on the roof of a Mitsubishi Evo which are specifically designed to introduce turbulence which reduces the amount of wake and thus drag - but even then the reduction in drag was minimal and the primary goal was to increase airflow to the large rear wing and increase rear downforce at speed.

Turbulence = drag. The only case where turbulence can reduce drag is by upsetting the boundary layer enough so that non-turbulent air can flow over the turbulent area and reduce the size of the wake behind the moving object. Look at golf ball aerodynamics.
 
There's quite a bit of "seam" on the front of the Leaf, what with the pop-up charging port and all. I'm wondering if it would be worthwhile to have some sort of silicone insert to eliminate those gaps. Anyone have an idea of what the real-world reduction of CD might be? I remember the blokes on Top Gear taping up all the gaps on their cars trying to go for top-speed on the salt flats. :roll:
 
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