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Old 05-08-2008, 12:37 AM   #1 (permalink)
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Lightbulb 2007 Honda Civic EX - A-pillar fins?

I've heard that some of the air that flows over the windshield is also "squished" towards the edges of the A-pillars. The "squished" air is then met by the air that is travelling along the side of the car, and then creates a vortex along the sides of the roof. The image I have in mind is an airplane taking off from a dusty runway and generating a vortex at the ends of its wings. (Picture a long curl/corkscrew being dragged through the air from the upper right and left of the windshield.)

Still with me? OK, for those who are here's my thought: What if I added relatively small fins that run from the bottom of the A-pillar all the way to where the roof "begins"? Shouldn't this improve the way the air would flow over the car, reduce turbulence, thus improving mileage?

I'd also imagine that this would reduce wind noise, but that is speculation.

Any thoughts?

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Old 05-08-2008, 01:19 AM   #2 (permalink)
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I think that based on the NASA van aerodynamics reasearch the leading face of a vehicle, even a completely boxy one like a van, is aerodynamically OK as long as it has 4" or so rounded edges.
Most cars A-pillars should be rounded enough to prevent any vortex-formation.
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Old 05-08-2008, 08:38 AM   #3 (permalink)
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I think an airplane's vorteces are a bit more extreme than a car. They're generated by the relatively high pressure under the wing leaking off the wing tips and meeting the low pressure on the top of the wing.

but if you want to try it i'd be very interested to see if you get good results! I think the same-ish principles would still apply, just in a less extreme manner.
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Old 05-08-2008, 11:12 AM   #4 (permalink)
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Thanks for the feedback. I noticed that sometimes in modern cars the windshield is recessed, as if to create an aerodynamic decive. But it could be just to direct the water that is wiped over the car, instead of letting it "dribble" across the side windows (as it did on our old car - the 1993 Oldsmobile Cutlass Ciera).

I noticed that adding more to those gi-normous a-pillars may obstruct visibility even more, but maybe I'll have to use some see-through material.

I'll tinker and will post the results. Thanks again!
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Old 05-08-2008, 10:09 PM   #5 (permalink)
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Hi All,

The A pillar fins were shown in the one of the next Gen Prius concepts. The latest scuttlebut is that will be the Lexus version of the Prius.
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Old 05-10-2008, 02:12 PM   #6 (permalink)
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Quote:
Originally Posted by superchow View Post
I've heard that some of the air that flows over the windshield is also "squished" towards the edges of the A-pillars. The "squished" air is then met by the air that is travelling along the side of the car, and then creates a vortex along the sides of the roof. The image I have in mind is an airplane taking off from a dusty runway and generating a vortex at the ends of its wings. (Picture a long curl/corkscrew being dragged through the air from the upper right and left of the windshield.)

Still with me? OK, for those who are here's my thought: What if I added relatively small fins that run from the bottom of the A-pillar all the way to where the roof "begins"? Shouldn't this improve the way the air would flow over the car, reduce turbulence, thus improving mileage?

I'd also imagine that this would reduce wind noise, but that is speculation.

Any thoughts?
The "squish" is okay,as its just the deformation of the free-stream as it accelerates around the A-pillar.The discontinuity of air velocity between this area and the flow over the roof can create the vortices.You may see these on a rainy day,as water droplets may be stalled within this area outside the door glass above the side-view mirror.Airplanes and GTP cars etc. use convex windshields which accelerate the air over and above equally,preventing the formation of the vortices.Modern cars have integrated drip rails ( developed by Hucho et al at Volkswagen in the 1970s) and have been extremely effective in reducing,if not eliminating these little tornados.Adding the fins may actually exacerbate the situation as they themselves will produce interference drag.You need some good visuals to know where your at before you begin.If you don't have flush glass you may be stuck.Any surface irregularity can trip the flow.

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