Help choosing vortex generators

[ConnClark]

Originally Posted by MetroMPG

According to the Mitsu report, the Airtabs are ideally sized (height wise) for the boundary layer thickness at the rear of the roof (about 30 mm). They're very close to the same height as the fin style VG's Mitsu employs.

Form the air tab site
"Each Airtab® generates two vigorous counter-rotating vortices 4 to 5 times the height ofthe Airtab® and several feet in length before bursting
"
Thats far taller than it needs to be for boundary layer tripping on a small car.

Also I found this post on autospeed from the airtabs inventor at the bottom of the page.

Browser Warning

A good read.

That said, VG's are a waste of time for significant (or even detectable) fuel consumption reduction.

There's much lower fruit to be picked elsewhere.

I agree with you here. And for the average person you are more likely to do more harm than good.

[Christ]

Originally Posted by MetroMPG

There's much lower, sweeter fruit to be picked elsewhere.

Fixed.

[noeryan]

Hey guys,
I'm new to Ecomodder. Love the site. I've been interested in Vortex Generators (VGs) for a little while now and have been doing some research. I'm a senior in Aerospace Engineering so it is fairly easy to weed through the b/s I read on the subject.

VGs are tricky. The placement of the VGs are key to their effectiveness. They draw faster moving air down in a spiraling motion to the bottom of the boundary layer of the vehicle which stalls the seperation of the flow a few inches. VGs create drag themselves but the smaller seperated airflow behind the vehicle lowers drag. Misplacement of the VGs can actually increase the drag due to poor placement and the vortices not stretching an area of the vehicle that could benefit from it.

Research per vehicle model should be done on vortex generator placement.

Out of curiosity, what would you guys pay for a researched VG system that dropped your Cd roughly 3-5%?

Also, would you be willing to place them on more than the roof of your vehicle (a flaw I see in most applications)?

Thanks guys!

[Deezler]

Unfortunately I wouldn't pay anything for a 3% reduction in Cd.. since it wouldn't be noticeable whatsoever in terms of fuel economy. Do you mean reduction by 0.03? b/c that would kick ass.

How would you do your research? PC based CFD trials? You'd be hard pressed to prove your results in the real world, I think. You should probably just run your research and tell us all the results for free. :P

Mitsubishi achieved over 15% reduction in Cd with their application of VGs....

[noeryan]

You are right about the 3% but I didn't want to promise something I'm not too certain I can reach. If it were 15% like Mitsubishi you can guarantee I'm gonna have a kit made and be talking to Summit racing

[noeryan]

Oh and how I would research it? I have access to a water tunnel and a few wind tunnels at school but I'd like to build a personal water tunnel so I can have access to it any time I wish and spend as much time on it as I can. I've priced some pumps that would be needed for the water tunnel and it gets pretty pricey. I'd like to have some type of product being developed to ease my mind about the price tag.

Wouldn't it be pretty cool to do some flow visualizations of all our vehicles?

Let me get some more thought in the water tunnel before I start promising stuff but a water tunnel for the forums would be pretty cool.

[Frank Lee]

I've seen people claim to do "water testing" by spraying their vehicle with a garden hose! LMAO!

[noeryan]

Thats funny. I guess it would give you some direction as to how the air is traveling around the car. It doesn't just go straight up and over. Obviously it takes the path of least resistance which makes the sides of the car a lot more attractive the closer you get to them. I like to watch the rain roll off of my windshield and picture the flow.

[Johnny Mullet]

I did some testing with these things. Specifically, the Airtab...................



I ran 4 tanks of fuel and noticed no increase in my fuel economy. Of course the snow, wind, cold temps, etc do not help either. I will say one thing good about them though! The keep my rear window totally clean!

[noeryan]

They look nice. It seems to me without any actual data to back it up...that putting the vortex layer at the top surface of the vehicle may increase the fish tailing vortices on the sides of the vehicle. The top surface isn't the only one that has seperated flow. Also, did you research or test where to place the airtabs? I'm fairly confident they can be properly placed and one can achieve a better fuel economy.