Vortex generators
 

The guy in this video below blabs on quite a bit but at the 6min 30 sec mark he starts showing his experiments. I was quite intrigued by what exactly was happening. then on a video down the line the show vortex generators on an airplane wing reducing the stall speed of the plane from 60 knots to 45 knots. definitely some serious aerodynamics going on with those little flaps. my intention is to incorporate these to improve airflow around the side of my car. https://www.youtube.com/watch?v=9Whd_KnsLKE

A lot of nae-sayers out there but I plan on trying these myself. Invented for planes yes (even improves R/C planes), but a LOT of trucking companies are using them now. I can see an advantage to a semi but I am still skeptical about a car.

? About 6:20 he's saying he dramatically decreases the drag by purposefully stalling the wing. I doesn't that mean when the VGs are not deployed? And then when he dramatically increases down force, is when the VGs are deployed, causing attached flow.(but increased drag)

check it

Airtab | Aerodynamic Fuel Savers | Welcome

Feel free to be the first ecomodders to ever get any results with VGs. Be sure to let us know how you did it.

Nay.
1st Issue- The air is already turbulent on the skin of a car, you're only making it more turbulent.

2nd Issue- The air in the first 2 inch layer of the car is only .05% of the air being moved about by your car. There is a lot of air moving 10 feet on top and to each side of your car, and for hundreds of feet behind it. A .05% change in the air movement can not create a noticeable change in the drag.

3rd Issue- There is a certain amount of drag created by the "Vortex Generation" itself. In order to make a positive difference, the newly invigorated air would somehow have to not only overcome the drag it just produced, but it would have to somehow create less drag down stream. On any modern automobile, this simply isn't going to happen. Maybe some crap box from the 70's or 80's, but other than that, you'll only be shooting a squirt gun at the Hoover Dam and expecting it to improve it's performance.

4th Issue- Cars are not airplanes, they follow vastly different aerodynamic rules. Just the same......Please explain how a reduced stall speed equates to a lower drag? It is flim flam pseudoscientific jibberish designed to baffle and confuse. In fact, to generate more lift you must by definition create more drag.....think about it.....if by making more lift and LESS drag, you'd reach a point where a 400 foot wing span on a piper cub would be the ultimate flying machine with almost zero drag and the ability to lift hundreds of tons with a 95hp motor going 450 MPH getting 50 MPGs doing it. Yeah, that makes sense.

With VG's in respect to fuel savings, you need to give it some serious skeptical analysis and then just......

http://i59.tinypic.com/e7173d.jpg

V.G.'s
 

The Mits article (found the PDF recently) detailing the V.G. test, did say .006 (6 counts) less dag & reduced lift. Different tests showed airflow hugging rear window more & made rear wing more efficient.
Doing a trailing edge design myself at moment using V.G.'s rotated to keep air from curling under so much or less energy in after-car vortex.
Enjoying the Kyle Drives videos myself. I like the scientific approach & detail he uses.
1st time poster here...Read for years. Be easy on me guys...

Like a lot of mods we do on this site, these seem like they may only work in our minds. But then again, if you put them on your car and feel like a winner, haven't you still technically won?

I have a grill block, aero side mirrors, moon discs and a stubby antenna on Ron Burgundy. Total net mpg value, who knows? Total net value in my mind, priceless!

My little mods so far, with careful driving habits mpg up 30%...worth it to me (consistant +40 average highway.

VG = diminishing returns

So, the question becomes 'are they worth the effort'?

Since the placebo effect is so rewarding, "yes".

On a plane VGs keep the air attached to the wing longer and put more air on the flaps to give it more control at slower speeds. Removing separation. On a car it should do the same thing of removing separation and giving a cleaner break at the back. I'm sure it is not a measurable boost to FE but they look cool. lol. (Not airtabs but the Evo style) Even so, just because a few people try something with no results is no reason others shouldn't try. Otherwise we'd all still be in the stone age.

I'm not arguing they in fact work. And I know from lurking here for years that this is beating a dead horse. And I'm very skeptical myself. But I'm still going to try.

i will leave this here. however i am not convinced yet GasPods - Saving Fuel with Roof Attachments | Tundra Headquarters Blog

Gaspod vortex generators are so aerodynamic they'd barely do their supposed job anyway

Real science behind them...
Aerodynamics Research Revolutionizes Truck Design

Like any aeromod, you need a special case to see a big effect. Eddie's video shows a special case. Incremental beneficial aero effects are small, with large downsides when done poorly. On most modern cars, the latter generally dominates as factories have wind tunnels and real engineers; if VGs were aero-salvation, they'd be on the cars now.

Have fun,
Frank

He wouldn't be the first.
Darin tried them with some results - lots cleaner air over the rear window
I tried them (glider dimple tape) with some results - they quieted down A-pillar / mirror noise quite a bit and changed the airflow pattern over the side window.

The result however, was NOT fuel savings ;)

And change the flow pattern while you're at it.

Driving in the rain showed me that VGs actually work.


Even glider dimple tape WAS working, I'm talking about 1 tot 2 mm high (1/25 to 1/12th of an inch) protrusions here ...

But that layer dictates what the rest of the air is doing, and how smoothly it'll do so ...


Yup.
That's why VGs were intended for square boxes: RVs, trailers, ... and the like.


Gliders operate in much the same speed range though - and they do use dimple or zig-zag tape (be it on aerodynamically cleaner designs)


Beyond solving local airflow issues and buffeting, VGs are typically used to make the airflow remain attached to high-lift devices (flaps) on the rear of a wing
Essentially they "bend" the airflow.

And that's the useful feature on cars : make the air follow curves and angles where it'd normally detach from (causing high drag)

Or reduce lift under the nose

I've had Airtabs on the back of my Dodge Magnum and Jeep Grand Cherokee (just across the top) for years, but my main purpose is to keep the back window clean while driving on the highway. Works great for that, and as said, there are no FE gains, but that's OK with me.

#4, VG had shown to reduce wing stall speeds from 60 to 45MPH, do you believe this is not applicable to cars?

#3 True that cars are much more aerodynamically optimized now, than they were back in 70s. Also true, VGs have drag by themselves. However they can be used to improve already existing aerodynamic features of the car.

For example placing VGs ~1'+ in front of hatchback/SUV/minivan roof spoiler increases speed of air stream at the edge of spoiler, and makes it more efficient in reducing trailing wake. I suspect placing them on the hood in front of windshield could be of benefit, but this needs to be looked in combination with wipers.

They are on every Formula 1 car, aren't they?

they'd be on
 

Somewhere in my reading,it was mentioned that automakers considered VGs.They'd have to be stamped into the sheetmetal for mass production,they'd be a challenge in a carwash,and in a pedestrian impact,if the person somehow made it over the roof,VGs would ad injury to injury.:o

Found this article:
Aerodynamic Effects of Rear Spoiler and Vortex Generators on Passenger Cars (PDF Download Available)
There is more in article, but it is clear that at least in combination with rear spoilers VGs help to reduce aerodrag.

clear
 

It is only clear in the context of the specific vehicle investigated (Mitsubishi Lancer?)
Since VGs were intended for notchback type cars,the caveat to VGs would be,if you have a notchback car very much like the Lancer,then there is an opportunity to see a very small drag reduction with the addition of properly-sized and positioned VGs.
No broad and sweeping claims can be made to the otherwise.

.....if you get to try no less than 26 combinations with unlimited wind tunnel time? Given that, you could probably find a configuration of gluing bricks on that helped. I'd be more curious what their results were in their 1st attempted configuration

Edit: ok, is the +45 spoiler a lift and drag inducing worst case scenario no one would ever use ever? Or am I seeing it wrong

I agree with you that VGs are not a magic item which gives you higher MPG by just having them, and use of them should be looked in context. What I specifically refer to is that VGs when used properly can help to increase efficiency of properly designed spoilers by increasing speed of flow and decreasing spoiler stall speed.

If not used properly they will do nothing or hurt, but this can be said of any aero mod.

Edit: not sure which vehicle they used. There are more production cars/SUVs use them now. I followed hybrid Avalon last night it had OEM VGs on rear underpan.

My biggest issue is that we don't even know what is the car configuration. Sedan? Hatchback? How aero iit was before they started? So there is not enough information to be useful in designing aero efficient vehicle.

What is encouraging that study confirms that properly positioned VG and spoiler combination works better than spoiler alone, and VGs when used properly can improve aero efficiency.

As someone who has looked into this in depth, vortex generators can work on a car. Want proof? Mitsubishi actually did implement them on their Evo Lancer and got a 2 to 4% reduction in drag. The problem is they needed to do a full CFD simulation and a wind tunnel to verify it.

With my old 300SD I did some CFD simulations and was able to get about a 3% reduction in drag. Would it have saved me any fuel? not really because my most of my driving was in town and short trips.

What I learned from the simulations.

1) Sizing the VGs was very important. If they were too big they just created drag. In other words don't expect VGs designed for semis to work for your car(they might but it won't be optimal).

2) Proper placement is very important.

3) To get VGs to work where you want them to you might need to address problems further up stream.

4) the number of combinations is infinite so you will never find an optimal solution.

5) Unless your car's aerodynamics is absolutely abhorrent don't expect to get more than a 5% improvement

Found this on Toyota's website: "Turbulent air increases drag, which adds wind noise and reduces efficiency. Camry features small, specially placed design features called vortex generators to help smooth things out. Not only do these help Camry maximize its efficiency, they help keep things quiet inside the cabin too."

I think this refers to the small VGs manufacturers today use on exterior mirrors and taillight and headlight lenses (my Prius has a single VG on each headlight, molded into the clear plastic), but they are VGs nonetheless, and if they didn't do something the manufacturers wouldn't go to the trouble of using them. That said, they are very small in size and number. Slapping VGs on the back of a car willy-nilly is an exercise in futility.

I'm remembering just now, too, the wing on the back of the SRT-10. It had a trough on the underside, about an inch long, that ran the width of the wing.

https://theviperstore.com/images/RAM...Cover_SR11.jpg

Hard to see in this picture (not my truck), but it's there. I seem to remember Dodge claimed the trough gave a slight improvement in aerodynamic efficiency versus a spoiler with no trough. With the standard tonneau cover in 2006, however, the wing was redesigned and the trough was gone.

I am not sure starting when but hycam and hy Avalon have little tabs under rear bumper. Prius C has 2 tabs on tail lights and one on mirror.

spoilers
 

I think it's time for images.
Are we talking 'wings' or 'spoilers'?
If VGs allow the inviscid flow to more closely follow the aft-body contour of a car,it won't really alter the local air velocity.
A wing will already be above the separated flow in 'clean' air and little affected by VG modification.
If a spoiler is in separated flow,VGs can help with reattachment onto the boot/spoiler,a clear advantage.
A spoiler doesn't have a stall speed.It's just a reattachment apparatus on a car with designed-in separation.
And with a wing,the VGs would have to be on the wing itself to be able to alter its stall characteristics,something well researched since 1920.
The other thing,is that there are about six different types of VGs in use.Each has a specific advantage.All six types would want to be investigated.And their performance depends on the local boundary layer thickness,along with orientation,location,and spacing.
They require a wind tunnel for investigation.If you're going to do a moving-floor tunnel as is available in North Carolina,you're looking at $4,000/hour for testing.And you'll be there for days.
I agree that VGs have their place,but we may be forced to leave it up the the Mitsubishi's of the world to figure out how to best use them.

tabs
 

A lot of these are added after time in an anechoic wind tunnel,where wind noise was discovered.The tab changes the resonant frequency of the part,killing the noise,and very little is spent on tooling modifications to mass produce this change.
The EPA has stringent noise criteria for cars.Even tires.

One should note that noise takes energy to create :)

Regular Camry has Cd .28 and hybrid .27:
2016 Toyota Camry Hybrid LE Specs, Options, Features, and Dimensions | Car.com
2016 Toyota Camry LE Specs, Options, Features, and Dimensions | Car.com