a question for the aero guys!

[Frank Lee]

I don't know how hard it would be to make it work. Aerohead turned us on to a way of correcting downstream flow on square-edged forms like trailers and camper shells and even truck cabs and it was a curved "leading edge fin".

[MetroMPG]

Originally Posted by NickelB NL

To make it big enough to not let it spill the high preasure and to make it flow nice

It's going to spill regardless. The idea of the curved portion Frank mentioned is to control the spill in a way that keeps the flow "clean" along the sides.

I'm going to play devil's advocate here, but I think automakers have already put a lot of time into optimising A-pillar design for current windshield angles. Short of fully encapsulating & shaping the whole front end from the leading edge of the hood to the roof (which requires adding a second windshield), I don't think there's much to be gained.

[Frank Lee]

And if there's a rear view mirror there it might negate any benefit.

New Civic A-pillar/windshield relationship is kind of similar.

[2000mc]

I'm afraid it would be like working with a box plow. no flow over the edges, unless you keep going until it's full. Then you're still spilling over, but you'd be pushing more at the same time.

[spacemanspif]

I have to agree with Frank, the civic has a recessed windshield with a protruding a-pillar and I believe the new Focus and Fiesta have a similar set design. There was a post on here about Mercedes experimenting with a-pillar fences but can't remember it off the top of my head. Also, doesn't the old Beatle benefit from such fences? I'll have to do more digging when I'm not on my phone...

I think the original idea is a neat one just to try and block so much air coming into contact with the side mirror. Let the air up the pillar spill over like normal, but redirect some flow away from the problematic mirrors... Some triangles of coroplast should be easy enough to cut up and stick on for testing. Tuft test the windows and sides of the car and only treat 1 side so you can compare if there is extended turbulence on the non-treated side. I'm assuming the faster you regain attached flow, the better off you are.

[Joris]

The Eolab has fences, but the air can flow through them. They must have done that for a reason.

[serialk11r]

Originally Posted by Joris

The Eolab has fences, but the air can flow through them. They must have done that for a reason.

I first thought it might be for structural reasons then I realized that is probably not the case. Perhaps the fences help bend the air around the A pillar so there's less vorticity.

[freebeard]

It might make things worse. If the mirror is visible from the front of the car, it's part of the frontal area. Blocking the flow off the windshield might change the angle of the oncoming air, but that would drive the drag toward similar to the stagnation point.

spacemanspif mentioned old Beetles. This is cribbed from racing 911s:

http://www.gerrelt.nl/section-aerodynamics/aerodynamics-vitaloni-mirror.html

Mirrors are problematic because the optical requirement demands a flat plate and they are located in a complex flow. Peep mirrors and fendertop mounted mirrors address this. Peep mirrors are closer to the drivers eye and can be smaller.

The Eolab is interesting. I wonder how much of that is not just styling. Ferrari took the opposite approach...once.

[renault_megane_dci]

Originally Posted by serialk11r

I first thought it might be for structural reasons then I realized that is probably not the case. Perhaps the fences help bend the air around the A pillar so there's less vorticity.

Nothing fancy : the windshield angle is steep so there is less heavy glass but it wouldn't look aero from the side so they made fake A pillars which didn't detract flow (measured).
Aero performance is very much in the back of a car anyway.

[aerohead]

Originally Posted by NickelB NL

I.ve been thinking about it for days now. Afther reading a bit into mirror designs and the high preasure at the windshield and high turbulance around the a pillar.

What about spoilers/flaps to fill in the angle between fender and a pillar. A flat plate welded in or if ducktape wil hold for testing or other manners. But i my mind if you box in the high preasure at the base of the windshield and "cut" the air with the same plate for better attached flow on the sides and around the mirrors. Sorry for my schetchy explanation. I.ll try to make a hand drawn schetch and upload it

The stagnation bubble atop the cowl area is not responsible for flow over the windshield or A-pillars.It doesn't go anywhere,but rather travels along with the car,stuck right there.When the ventilation damper is open,this pressure pushes air into the HVAC system.
In a rain,you may see the air (pushing water ) go sideways at the bottom of the windshield,at a 45-degree angle at the top sides,and vertical in the center.
As MetroMPG mentioned,if you place a capping plate/fence near the A-pillar base,the transverse flow will trip over it,creating flow separation and turbulence right there.
Modern cars which have the valley between the A-pillars were designed for that.The fenders,hood,windshield,and A-pillars were all done from scratch to accommodate that feature.To dial that in on a car not designed for it might not be doable.If it could,you'd need,according to many new graduate engineers,and also mentioned ,top of the line CFD or a full-scale wind tunnel.
Personally,I'd recommend you spend your time elsewhere.