Wind tunnel picture of headlight / mirror airflow

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TEG

Well-known member
Joined
Jun 10, 2010
Messages
1,388
I am not sure if this was posted before, but the topic of funny headlight shape to direct airflow away from the mirrors (to reduce noise) has come up repeatedly...

 
Nice - side mirrors are notorious for the drag they introduce as well - I wonder if moving air around the mirrors increases or decreases drag - or maybe the effect is negligible?
 
palmermd said:
noise=drag...I'm sure the reason was drag and the noticeable benefit was noise reduction.
Yes, but moving air around also creates drag. There is no free lunch here. Otherwise you'd see more cars with this feature.
 
drees said:
Yes, but moving air around also creates drag. There is no free lunch here. Otherwise you'd see more cars with this feature.

Yes, but doing it gently is less disruptive than doing it abruptly hence less drag and less noise. Otherwise all cars with the same frontal area would have the same drag.
 
drees said:
palmermd said:
noise=drag...I'm sure the reason was drag and the noticeable benefit was noise reduction.
Yes, but moving air around also creates drag. There is no free lunch here. Otherwise you'd see more cars with this feature.
I have. I've noticed several cars recently with bubble headlights. None quite as prominent as the LEAF, but obvious enough.
 
palmermd said:
noise=drag...I'm sure the reason was drag and the noticeable benefit was noise reduction.

I think Nissan has said that the reason was the noise. The car is otherwise so quiet that the noise from the wind over the mirrors was a problem and Nissan's solution was to use the headlights to direct airflow away from the mirrors.
 
palmermd said:
Yes, but doing it gently is less disruptive than doing it abruptly hence less drag and less noise. Otherwise all cars with the same frontal area would have the same drag.
I wonder how much of a difference this makes on drag. I recently read (Car & Driver I think, but I forget exactly where) that side mirrors account for 7% of the a car's drag. I'm sure that's a generic statement and varies from car to car, but that's not a trivial amount. If this helps helps with drag in addition to noise, that'd be huge.
 
palmermd said:
noise=drag...I'm sure the reason was drag and the noticeable benefit was noise reduction.
kevin672 said:
I think Nissan has said that the reason was the noise. The car is otherwise so quiet that the noise from the wind over the mirrors was a problem and Nissan's solution was to use the headlights to direct airflow away from the mirrors.
The "host" at the "Drive Nissan LEAF" event I attended in late 2010 said the same thing. At the time, I thought to myself, "And, of course, the battery is built by bachelor Norwegian farmers so you know it's good for you." Now, all I need to do is to find proof that the pic above is not a Photochop job! :D
 
They should put fan generators right where the wind passes, VAWTs that charge the pack. That would probably add 20 miles on the highway. Those plus a larger solar panel and the car may drive perpetually in the sun.
 
EVDRIVER said:
They should put fan generators right where the wind passes, VAWTs that charge the pack. That would probably add 20 miles on the highway. Those plus a larger solar panel and the car may drive perpetually in the sun.

Or just drive forever downhill (by the way, I think the sun powered car has already been done several years ago).
 
aqn said:
Now, all I need to do is to find proof that the pic above is not a Photochop job! :D

I noticed that this picture is also on Nissan's website (http://www.nissan-global.com/EN/STORIES/VOL03/02.html" onclick="window.open(this.href);return false;) if that helps.
 
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