windshield airflow

[lunarhighway]

some ideas i had:
A:
from what i read on the web "a-pillars" apparently create a big vortex at the side of the vehicle wich is said to be responsible for a lot of wind noice (most research seems to be aimed at wind noise reduction) but this vortex probably has a very undesirable effect on drag as well.

i'm wondering if installing vorex generators to the side of the A-pillar might succeed eleminationg this big vorex and at the same time keeping more airflow attached to the side of the vehicle?

B:
also i noticed that most modern vehicles hood curves upward leaving a recessed area for the wipers. on my car the wipers are frightfully exposed to the airflow. i'm considdering inserting a strip of about 5 cm's high in front of them at the rear hood seam, and angleing this strip at the same angle and curve as the windshield...

i realise that the transition hood/fairing should be more smooth but since this is not the case for the original hood/ windshield transition anyway there should be no aeordynamic changes in this respect.

any thoughts on this approach?

(after posting i noticed this post should go under "General Fuel Economy Discussion "....sorry)

[lunarhighway]

here's a scematic of what it should look like

[MetroMPG]

When VGs are used to promote non-turbulent airflow over a curve, they need to be placed upstream of the separation point. I'm not sure that putting them on the a pillar itself would work because it's probably not far enough upstream from the transition, and also the angle is relatively sharp.

The wiper fairing idea seems OK. I know a few people have done this (or plan to).

[Ted Hart]

Originally Posted by lunarhighway

A:
from what i read on the web "a-pillars" apparently create a big vortex at the side of the vehicle wich is said to be responsible for a lot of wind noice (most research seems to be aimed at wind noise reduction) but this vortex probably has a very undesirable effect on drag as well.

i'm wondering if installing vorex generators to the side of the A-pillar might succeed eleminationg this big vorex and at the same time keeping more airflow attached to the side of the vehicle?

B:
also i noticed that most modern vehicles hood curves upward leaving a recessed area for the wipers. on my car the wipers are frightfully exposed to the airflow. i'm considdering inserting a strip of about 5 cm's high in front of them at the rear hood seam, and angleing this strip at the same angle and curve as the windshield...


any thoughts on this approach?

(after posting i noticed this post should go under "General Fuel Economy Discussion "....sorry)

Sorry? I posted(still do) under the wrong slots many times...they get read!

First, a comment on your windshield wiper placement...relax! The wipers nest in the stagnant air at the base of the windshield. It's (relatively) quiet down there ... little or no drag. Hint : Watch the raindrops next shower.... Wiggling 'drops aren't pushed by air (no definite velocity), just a bit of chaos. The streaming drops are where the velocity lies... and the drag potential.
Next, a comment on vortex placement .... The side of the pillar(s)? A vortex generator requires energy to spin ! This energy is called "drag". Imagine holding a plastic pinwheel out the window...at the windshield base (or wherever). It will last a micro-second before self-destruction at speed ! Vortex generators do one thing very well! They lighten the wallet!

[lunarhighway]

thanks for the advice...
the a-pillar vortex i'm talking about comes from this document :
http://www.exa.com/newsite/PowerFLOW...acoustics.html

the idea of adding VG's to the pillar would be to break this up into smaller vortexes rater than try to keep the air attached to the vehicle directly...

it's just a thought though... and the actual effect of anything would be hard to detect... but i might try to ad some homemade vg's there at some point, just to see what it does ( looking at the shape of aircraft vg's it shouldn't be a poblem to make them inexpensively maybe i'll even use card for testing)...
i added 2 tape covered card fins at the outer edge root of my windshield today.
i noticed an increase in noise at speed and sticking my hand out of the window there seemed to be more airflow beside my window. i won't draw any conclusions from this but it's encouraging to keep trying...
more "testing" to be done

[Ted Hart]

Originally Posted by lunarhighway

thanks for the advice...
the a-pillar vortex i'm talking about comes from this document :
http://www.exa.com/newsite/PowerFLOW...acoustics.html

Hi, again!
I just looked at the link you provided...and I see what you're refering to...wind noise (we used to call it "buffeting"). The vortex at the top of the pillar is where the roaring comes from...remember the days of the vent window? they're gone now...the stylists and the beancounters got 'em!
Vehicle drag is always present, especially in the areas of corners. Whenever you separate laminar lines of flow you'll find vortices (and the drag associated with them)! Filling the low pressure zones with air from "somewhere else" works to reduce the low pressure ("Nature abhores a vacuum", right?).
The absolute easy way to reduce these swirls is to slow down... in lieu of / in conjunction with?... that, fill 'em in! Idea: Try filling in the area with a pitot tube arrangement(just a length of plastic tubing)...taken from a high pressure (ram air source ) in the front of the vehicle..., pitot tube protruding a bit from the chaos zones. You might as well use that pressure zone(stagnant air pocket) for something!

[lunarhighway]

Originally Posted by Ted Hart

remember the days of the vent window? they're gone now...the stylists and the beancounters got 'em!

i think my dad's prevous cars used to have them he used to have them.
he's subsequently owned 3 or 4 opel rekords c coupés... it's also the first car i learned to drive in. http://upload.wikimedia.org/wikipedi...e_vl_green.jpg
(this is just an example the one's i remember where golden-brown and white). the car was very sleek looking,but getting all the weight on the move took quite some energy... fortunately it's appearance caused most drivers to slow down a bit ... the last one started to become impractical as a dayly driver and with no place to store and restore it, it had to go...i think FE was close to terrible as well

Originally Posted by Ted Hart

Filling the low pressure zones with air from "somewhere else" works to reduce the low pressure ("Nature abhores a vacuum", right?).

...

interesting... i suddenly got an idea...why not use all the "tubing" that's already on the car? the intake of my heater/ventilator is located as the windows base, probably as the high pressure forces it in... right?... there are also 2 additional outlets on the dash aimed at the side windows to defog them.......they're pretty close to the side mirrors...
it wouldn't be too difficult (al least in theory...) to route this air trough to the side mirrors for example... first of all having cold or warm air come out of the sidemirrors might come in handy in the winter ... but it might also be used to reduce the mirrors wake?perhaps a directable outlet could be interesting too.. of course it might not be a good idea at all but if i can find a relative easy way to try this i might give it a shot...

[Maillemann]

Originally Posted by lunarhighway

B:
also i noticed that most modern vehicles hood curves upward leaving a recessed area for the wipers. on my car the wipers are frightfully exposed to the airflow. i'm considdering inserting a strip of about 5 cm's high in front of them at the rear hood seam, and angleing this strip at the same angle and curve as the windshield...

You mean something like this, right?



(Lund Wiper Cowl)

I've wanted to put one of these on a vehicle for years, but will have to fabricate my own since they're mostly made for trucks. Not a big deal, used to working with thermoplastics, but have always wondered if it's a benefit or detriment to airflow. Visually seems like an obvious improvment, but could that big gap that's being created just cause more turbulence? Anyone know?

[Lug_Nut]

Yeah, I know. It will just fill up with snow.
Can you tell there's a forecast for another 6~8 inches with rain on top to make it really heavy?

Oh, It'll also obscure my state's annual inspection sticker, a legal no-no here leaving me liable to a fine. I don't think a clear one instead of the tinted one in the image above would be acceptable, either.

[skewbe]

One could also park their wiper blades up and down for a cheapie fix, ie. pull the fuse at just the right moment or add a switch, or get fancy and put the crank on 180 degrees out or somesuch.

[Maillemann]

Originally Posted by Lug_Nut

Yeah, I know. It will just fill up with snow...
Oh, It'll also obscure my state's annual inspection sticker...

Indeed, both these things occured to me, as well as the invariable attendant accretions of leaves and pine needles. I agree from this standpoint they are less than ideal, but I'm still curious about their effects on aerodynamcs, be it positive or negative.

[lunarhighway]

just think of how cool it would be to have this colosed of with a lid that electrically opens when the wipers are activated... or maybe just the whole fairing folding against the window

extra weight and electrical load from such a setup would probably cancel out the benefits but than again there was a time when every sporty car seemed to have pop up headlights so who knows?

anyway so far i've installed flatblade wipers a while back... so i'm a littel less eager to shield them from the airflow

they look really sleek although at low speeds they don't quite deliver enough pressure on the blades... i might have to tweak my arm's ... to bad they still attach to the center of the blade... would be cooler to have wiperblades/arms in one single piece flat piece. jugeing from the rainpatterns they do have an effect on the airflow when not in use, but i haven't been able to see their effect in my FE

[zpiloto]

Originally Posted by Maillemann

You mean something like this, right?



(Lund Wiper Cowl)

I've wanted to put one of these on a vehicle for years, but will have to fabricate my own since they're mostly made for trucks. Not a big deal, used to working with thermoplastics, but have always wondered if it's a benefit or detriment to airflow. Visually seems like an obvious improvment, but could that big gap that's being created just cause more turbulence? Anyone know?

That area is dead space with the angle of most windshields. Because of the turbulence the wiper drag in not going to be noticeable. I did a couple of runs with a shield like the one on the truck except mine went straight to the windshield, no gaps, without any noticeable increase in FE. I figured the use of wipers was more important. I think if you really wanted to increase the FE you need to put a wedge from the front of the hood to about 6" up the windshield.

[cfg83]

zpiloto -

Originally Posted by zpiloto

That area is dead space with the angle of most windshields. Because of the turbulence the wiper drag in not going to be noticeable. I did a couple of runs with a shield like the one on the truck except mine went straight to the windshield, no gaps, without any noticeable increase in FE. I figured the use of wipers was more important. I think if you really wanted to increase the FE you need to put a wedge from the front of the hood to about 6" up the windshield.

Would this be a situation where a "hood lift" would help, i.e. where spacers lift the rear of the hood up? If 6 inches is too high for you, you could compromise between lift and style, and reduce the drag of the wipers. But I think you would need to fill in the triangular gap that is created on each side between the fenders and the hood.

CarloSW2

[zpiloto]

Originally Posted by cfg83

zpiloto -



Would this be a situation where a "hood lift" would help, i.e. where spacers lift the rear of the hood up? If 6 inches is too high for you, you could compromise between lift and style, and reduce the drag of the wipers. But I think you would need to fill in the triangular gap that is created on each side between the fenders and the hood.

CarloSW2

Mine opens from the front. It would be beyond my capibilities to lift it. Yes you would need to fill in the sides. I don't think this would be more than a 1-1.5% increase at best. I'll save that for when I get the mileage up to Little Blue country where I can see the effects.

[Lug_Nut]

Originally Posted by cfg83

Would this be a situation where a "hood lift" would help, i.e. where spacers lift the rear of the hood up? If 6 inches is too high for you, you could compromise between lift and style, and reduce the drag of the wipers. But I think you would need to fill in the triangular gap that is created on each side between the fenders and the hood.
CarloSW2

"Dropping" the front is more effective than raising the rear.
Re bumper removal: I had at some point of time a Civic 1200 (not the CVCC) with a mangled front bumper. The center was pushed back which made the ends stick further out (a reversed train's 'cow-catcher') to the point that it failed the safety inspection. I removed the bumper. Then it failed because of the brackets as "theClencher"s did. I just removed the offending brackets, too. It then passed with no problem.

[BluEyes]

Originally Posted by cfg83

Would this be a situation where a "hood lift" would help, i.e. where spacers lift the rear of the hood up?

You would have to also make a way to re-seal the rear of the hood to the cowl after lifting it. Otherwise, you've just made a great route for air to go under the hood and out the bottom of the engine bay under the vehicle. Very ugly airflow path there.

[cfg83]

BluEyes -

Originally Posted by BluEyes

You would have to also make a way to re-seal the rear of the hood to the cowl after lifting it. Otherwise, you've just made a great route for air to go under the hood and out the bottom of the engine bay under the vehicle. Very ugly airflow path there.

Ooof, I was hoping that gap would be benign. The "triangular" side shape is easier to build than the more complex (curved and styled) shape of the rear of the hood.

CarloSW2

[BamZipPow]

Originally Posted by lunarhighway

just think of how cool it would be to have this closed off with a lid that electrically opens when the wipers are activated... or maybe just the whole fairing folding against the window

extra weight and electrical load from such a setup would probably cancel out the benefits but than again there was a time when every sporty car seemed to have pop up headlights so who knows?

It would be easier to make it with a cam based using the wiper motor to open/close the fairing. When you activate the wipers, the cam would push the fairing up just enough to allow the wipers to clear. When turned off, the cam would allow the fairing to close after the wipers have retracted.

One might even incorporate a clear lightweight fairing onto the wiper arms themselves...kinda like the transformers movie.

[basjoos]

Here is the windshield wiper windscreen that I installed on my car. My wipers were definitely in the airstream, a fact made evident when driving in fog where the moisture would deposit on the lower windshield in a pattern reflecting the wipers upstream.

[lunarhighway]

cool



i still haven't gotten round to building something similar but i recently came across this article

http://www.autospeed.com/cms/A_2445/article.html

FE improvements seem limited but than again they did tested it on an old prius... the wipers do have their own pocket... mine just sit there facing the airflow.

i use flatblades now... a bit pricy and average wipe quality, wich might be due to the standard arms not delivering adequate pressure, but the rubber is durable and they look much more aerodynamic when not in use, also they do actually wipe better the faster you go.

still the whole setup is an aerodynamic mess so if i can find some good material i'll try to make something like basjoos did. i think i can get away with a fairly small gap between the windshield and the fairings.... i justy have a hard time finding good stuff to make it from.

btw basjoos what are the vertical strips at the edges of your windshield? are they to prevent water from going over the edge onto the sidewindows? some newer cars seem to have windshields that are resessed quite a bit is this something similar?

[dosco]

Why don't you give the VGs a shot?

This is the "Experiments" forums, right?

[RoadWarrior]

I've always thought front window air deflectors may be a help for this because well designed ones make more of a radius with the A pillar and allow clean edge separation, so the flow can shed cleanly, then maybe reattach cleanly further back. Another thought would be to try a type of slat there, a director vane type thing. I used to think also that those windshield shades looked like draggy pieces of crap, but have been wondering if the ones that are slotted at the back end, might actually help steep angled screens turn the air at the top better and stick it to the top of the cab rather than it trying to carry on another foot or two and make a big vortex.

[Minicity]

On the topic of air moving around the A pillars, I have often wondered, and may possibly try this if no one else has, about the use of slats. STOL aircraft have used fwd wing slats to keep laminar flow over the wings at high angle of attack. Would the same be possible attached to the A pillar? or would it just be a source for added drag without any benifit?

[RoadWarrior]

yes, that's basically what I was meaning, didn't want to call it a "slat" per se though since I perceived a slight difference in how it would work.

[Minicity]

The other side to putting actual slats on the A pillar is that the would be subjected to a good amount of wind stress as the air would be traveling behind them as well. They would need to be fastened securely.

Anyone not sure of what wing slats are......
http://www.zenithair.com/stolch701/7-design-wing.html

[RoadWarrior]

Yeah, don't think it's a job for double sided tape. First you've gotta have a thin and rigid slat... difficult... unless you carve them from old skis or something... or a good hardwood maybe... or bend them from aluminum sheet... then you've pretty much gotta drill and tap holes in your A pillar to fix them good... or use an epoxy mount.. not real good for fine tuning position. Maybe could drill into the back of the A pillar, and have a "round the corner" mounting bracket...

[Minicity]

I had thought of making them from either 18 guage steel and welding it or rivited aluminium. Basically making a mini wing with airfoils and a spare which then be attached to a top and bottom base. Your right, it would have to be attached to the pillars by screws, welding, etc. The attachment points at the spar ends could allow for some movement to adjust as needed until an optimum point was reached.

[paladin_omega]

Originally Posted by cfg83

zpiloto -



Would this be a situation where a "hood lift" would help, i.e. where spacers lift the rear of the hood up? If 6 inches is too high for you, you could compromise between lift and style, and reduce the drag of the wipers. But I think you would need to fill in the triangular gap that is created on each side between the fenders and the hood.

CarloSW2

I've though about doing this after seeing Steve Soto's civic in a Honda tunning magazine. It hides the wipers nicely and the gap it creates could be filled with something.

http://www.hondatuningmagazine.com/f...ack/index.html