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Old 7th November 2013, 13:12   #16
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Default Re: What is a Vortex Generator-Functions and Use

The vortex generator in an airplane wing transform laminar flow to turbulent flow, because the boundary layer separation happens farther in case of turbulent flow as compared to laminar flow. This allows greater angle of attack and reduced stall speed. Also reduces the drag to some extent (increased skin drag, reduced form drag).

So what would these vortex generators do in a road vehicle?
The same things. There is no angle of attack or reduced stall speed ... but reduction in drag? I don't think it will be effective. In fact you may face increased noise from your vehicle since the vortex generator tries to tip the airflow into turbulence at lower speeds.


I believe they are there just for the "tashan" factor.

Perhaps if you driving a race car with speeds high enough to cause lift, and you have a rear wing to generate a downward force - the vortex generator will help the effectiveness of this rear wing (like on aircraft ailerons)


***
also think this way, each manufacture loves to claim a high mileage/fuel efficiency, if these really worked ... everyone would've offered it right from the factory.

Last edited by alpha1 : 7th November 2013 at 13:26.
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Old 8th November 2013, 00:59   #17
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Default Re: What is a Vortex Generator-Functions and Use

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Originally Posted by alpha1 View Post
I believe they are there just for the "tashan" factor.
Totally agree. While a little drag penalty may be reduced due to delayed separation of the airflow after it crosses the vehicle thereby reducing the low pressure area just behind the car and thereby reducing drag, the penalty associated with the increase in form drag, especially at the speeds at which normal road cars travel does not seem to justify the proclaimed advantages.
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Old 8th November 2013, 08:40   #18
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Default Re: What is a Vortex Generator-Functions and Use

Vortex generators have been used for decades in the aviation industry for all the reasons as stated above. Planes move a lot faster then cars, so you would expect the improvements in speed/fuel efficiency to be much larger.

In fact, vortex generator benefits in aviation are expressed in a few percent points at the very best.(e.g 1,5-3%) Which is a lot and very significant for a plane.

But your car appears to have topped all mankind's knowledge on the effects of Vortex generators. This is a true scientific breakthrough.

A little analogy: I'm an old git and going (slightly) bold. So about a year ago i started buying and using every product known to man to stop the bolding and get my hair back. I have spend a considerable amount of money on it. And I spend a considerable amount of time applying it in front of mirror. I am absolutely convinced it works and it shows BIG time. Nobody and I mean nobody, not even my wife has acknowledged this!! How can that be after spending all this time, research and money on it?

When you're enthusiastic, spend time, money and energy on something, you are very likely to get the results you want, even if others don't agree or won't understand. Its a well known trap in research circles.

If you're happy it makes your car go faster and its more efficient, good for you. enjoy.

Jeroen
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Old 8th November 2013, 10:07   #19
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Default Re: What is a Vortex Generator-Functions and Use

I don't think vortex generators are bullcrap on road going vehicles however on aftermarket installations their effectiveness may depend upon the vehicle and installation and only at highway speeds.

Autospeed article on vortex generators Part 1 to 4
"Positive gains can be achieved only by practical experimentation. That’s the downside – the upside is that the vortex generators are easy to temporarily stick into place with masking tape, and just as easily removed if they are not achieving the desired results."

http://www.autospeed.com/A_3058/cms/article.html
http://www.autospeed.com/A_3059/cms/article.html
http://www.autospeed.com/A_3060/cms/article.html
http://www.autospeed.com/cms/article...-Part-4&A=3061

http://hikickracing.blogspot.in/2011...enerators.html

http://www.formula1-dictionary.net/vortex.html

OEM vortex generators on ORVM of a Honda pickup
http://ecomodder.com/forum/showthrea...rrors-977.html

Last time on the NH44 the car displayed a slightly nervous behaviour at high speed, i would definitely love to try this out and see if it makes any difference at all. Thanks to captain slow's screenshot i was able to find an indian supplier on the net. I'm thinking of testing these on my car and if they're priced sensibly.

Those who are interested can check out the PDF files attached to this post.
1208.0177v1.pdf
HondaWTReportV6.pdf

The mitsubishi file which was linked to in the first page which doesn't seem to work anymore.
vortexgenerator-evo-mitsu.pdf

Last edited by GTO : 9th November 2013 at 16:04. Reason: Please avoid references to illegally high speeds, thanks!
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Old 8th November 2013, 12:41   #20
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Default Re: What is a Vortex Generator-Functions and Use

^ The Mitsubishi case file shows that the experiment was done at airspeed of 50 metres per second.
That makes it 180 kmph.

Perhaps achievable by breaking the law on the Pune-Mumbai or Pune-Bangalore highway (or pick any of your choicest roads).
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Old 12th November 2013, 19:59   #21
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Quote:
Originally Posted by alpha1 View Post
^ The Mitsubishi case file shows that the experiment was done at airspeed of 50 metres per second.
That makes it 180 kmph.

Perhaps achievable by breaking the law on the Pune-Mumbai or Pune-Bangalore highway (or pick any of your choicest roads).
The "autospeed" links essentially show the same. No effect at normal day to day speeds. You need to go pretty fast before you get any effects and see an improvement in fuel efficiency or any other effect.

When driving at those sort of speeds in India, I think you need to worry about very different things, like am I a total anti social ******* with no sense of responsibility to be driving at these speeds?

Just being subtle here, wouldn't want to offend anybody, but if you take your car up to speeds of well over 120 140 km/h on a public road, here in India, I think you need to get your head examined.

Jeroen
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Old 13th November 2013, 00:09   #22
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...Or you could think you are driving in a race circuit which we have in India, say the Budhh or the MMST track. No?

Quote:
Originally Posted by Jeroen View Post
When driving at those sort of speeds in India, I think you need to worry about very different things, like am I a total anti social ******* with no sense of responsibility to be driving at these speed
For any aero to take effect on road, a car should be doing better than 180Kmph, until then the spoiler/wing/cloth hanger along with these vortex generators are only cosmetic add-on.
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Old 13th November 2013, 12:55   #23
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Default Re: What is a Vortex Generator-Functions and Use

Quote:
Originally Posted by alpha1 View Post
Perhaps achievable by breaking the law on the Pune-Mumbai or Pune-Bangalore highway (or pick any of your choicest roads).
Not necessarily, Andhra Pradesh doesn't seem to have a speed limit for cars. NH44 runs through Andhra too.

http://www.aptransport.org/html/speed-limit.htm

Quote:
Originally Posted by Jeroen View Post
Just being subtle here, wouldn't want to offend anybody, but if you take your car up to speeds of well over 120 140 km/h on a public road, here in India, I think you need to get your head examined.
If you drive in India you need to have your head examined. Everyone who get on Indian roads need to get their heads examined. Doesn't matter if you are slow or fast, here people think slow = safe and fast = dangerous and doesn't give a damn about rules/regulations.

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Originally Posted by anachronix View Post
For any aero to take effect on road, a car should be doing better than 180Kmph, until then the spoiler/wing/cloth hanger along with these vortex generators are only cosmetic add-on.
Not necessarily in all conditions. Check out ecomodders.com (i'm a lurker there) for fuel efficiency gains from from aero mods, from simple additions like smooth wheel covers and drastic aero changes like rear kammback extensions at speeds of 60 - 70mph which is easily do able on our divided highways.

But for rear wing what you said is correct because to provide any useful downforce the speeds should be high. Here we are not talking about generating downforce but reducing drag.

People who post their findings on ecomodders have experimented, within their means, and has data to backup unlike most members here. Here most of the guys are only interested in ridiculing whatever is put forward based on their armchair experience, that is typical indian mentality.

If someone here has tested these things before saying these don't work then I'd take that input as valid. And at ecomodders they have mixed feelings towards these.
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Old 13th November 2013, 13:21   #24
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Default Re: What is a Vortex Generator-Functions and Use

Quote:
Originally Posted by Sankar View Post
Not necessarily, Andhra Pradesh doesn't seem to have a speed limit for cars. NH44 runs through Andhra too.

http://www.aptransport.org/html/speed-limit.htm
Are you really sure there is no speed limits in the AP state roads? The websites of most of our govt institutions are pathetic at best with respect to the information present.

I find it hard to fathom, because usually the rules (for most of the things governed by govt regulations) are something like this:
Speed limit on highway = 80 unless explicitly otherwise stated
Speed limit inside cities = 50-60 unless blah blah ...

(Just a fictitious example)

Quote:
Originally Posted by Jeroen View Post
Just being subtle here, wouldn't want to offend anybody, but if you take your car up to speeds of well over 120 140 km/h on a public road, here in India, I think you need to get your head examined.

Jeroen
LOL
I remember writing once on this forum that an average human brain has capability limit of processing info during running speed. Which makes it 30-40 kmph. And anything above this become hazardous.

Someone got offended and responded by saying that human fly aircrafts.

I responded by saying that aircrafts are flown by pilots (and ground control) who practice a lot of safety procedures, like maintaining kms of distance between two planes, maintaining minimum clearance from the ground, etc ... and of course there are no cows and dogs shaped monuments, and no pedestrians and cyclists taking a walk in the park.

So you are right in saying 120 kmph on Indian roads is absolutely foolish endeavor. In fact in my opinion, and surprisingly the Govt has been right in setting the speed limit of 80 kmph in most places, because anything above 60 requires a remarkable good luck ...

Last edited by alpha1 : 13th November 2013 at 13:43.
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Old 13th November 2013, 14:48   #25
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Default Re: What is a Vortex Generator-Functions and Use

With the little that I know of aero, the small aero changes will be effective only if the vehicle has a higher drag and drag varies with the speed of airflow and the speed we do in normal city is not enough to bring you any effect to see the positive effects of these aero bits that reduce drag.

The wings or vortex generators or splitters will help reduce drag and as you say it helps fuel economy as well, but the measurable difference of these small aero components will not be much in a car that will be used only on streets.

If we are speaking of performance, yes.

Quote:
Originally Posted by Sankar View Post
Not necessarily in all conditions. Check out ecomodders.com (i'm a lurker there) for fuel efficiency gains from from aero mods, from simple additions like smooth wheel covers and drastic aero changes like rear kammback extensions at speeds of 60 - 70mph which is easily do able on our divided highways.

But for rear wing what you said is correct because to provide any useful downforce the speeds should be high. Here we are not talking about generating downforce but reducing drag.

People who post their findings on ecomodders have experimented, within their means, and has data to backup unlike most members here. Here most of the guys are only interested in ridiculing whatever is put forward based on their armchair experience, that is typical indian mentality.

If someone here has tested these things before saying these don't work then I'd take that input as valid. And at ecomodders they have mixed feelings towards these.
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Old 13th November 2013, 14:59   #26
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Default Re: What is a Vortex Generator-Functions and Use

Those who believe that vortex generators don't work and only work at high speeds kindly share your little nuggets of wisdom to engineers at Toyota, because they seem to think that these do make a difference above 25MPH.

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Quote:
Aerodynamic features
a. Aero stabilizing fins are installed on the side faceof the rear combination lamp and at the base of theouter mirror
  1. Initiates aero vortices that accelerate airflow along bodyside
  2. Reduces weak boundary layer airflow near body anddraws the main airflow closer to the body
  3. Increases vehicle stability
  4. Effective over 25 mph

b. Underbody covers improve airflow
  1. Smooth underbody airflow
  2. Vortex generators accelerate airflow
Read more here: Prius Technical Presentation

On Honda Ridgeline pickup mirrors
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Quote:
Originally Posted by anachronix View Post
With the little that I know of aero, the small aero changes will be effective only if the vehicle has a higher drag and drag varies with the speed of airflow and the speed we do in normal city is not enough to bring you any effect to see the positive effects of these aero bits that reduce drag.
25MPH is just 40KPH i'm sure that 40kph is possible in city roads, atleast here its possible. Many small aero mods combined together would yield benefits. Each on their own would add their tiny bit to help, when combined the difference would be measurable.

Smooth wheel cover, flat underbody, properly filled tyres, critically placed VGs, front air dams, lowered stance etc.. Not all of these are possible on Indian roads.





OT:
India doesn't have a uniform speed limit set for its highways. States have the authority to set their speed limits.

Quote:
Originally Posted by alpha1 View Post
Are you really sure there is no speed limits in the AP state roads? The websites of most of our govt institutions are pathetic at best with respect to the information present.

I find it hard to fathom, because usually the rules (for most of the things governed by govt regulations) are something like this:
Speed limit on highway = 80 unless explicitly otherwise stated
Speed limit inside cities = 50-60 unless blah blah ...

(Just a fictitious example)
Mods pls shift this thread to shifting gears. There is nothing technical in this thread anymore.

Last edited by Sankar : 13th November 2013 at 15:13.
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Old 13th November 2013, 16:25   #27
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Default Re: What is a Vortex Generator-Functions and Use

Dude, If you find these minute vortex generators on the side mirrors, its not for increasing stability as the brochure says, but to cut wind noise as the mirror design could cause airflow separation and these vortex generators should help attach the airflow more smoothly and cut windnoise.

Similarly, if these vortex generators are on the edge of the C-pillar which is often the tail lamps of an hatchback is to smoothen the air flow. In a hatchback the wake is higher than the sedan and could cause lot of drag. The amount of drag depends a lot on the rear hatch design of a hatchback.

You can read more here.
http://www.autospeed.com/cms/article.html?&A=112609

To quote from the article

Quote:
Even quite minor changes in rear hatch angle can cause major changes in drag. Tests carried out by Volkswagen have shown that the Cd of the car can vary from 0.34 to 0.44 as a result of slight alterations to the rear hatch angle. At one angle (30 degrees to the horizontal in this case) the airflow separation point jumped back and forth from the end of the roof to the bottom of the hatch, depending upon the curvature at the rear edge of the roof. It was this 30 degree rear hatch angle that produced the highest Cd value.
Its normal to find these vortex generators on the big SUVs as they have higher Cd and these aero bits will definitely help reduce drag. Like I said earlier, the positive effects are felt with these aero bits in a car that has a higher drag coeffecient.

Quote:
Originally Posted by Sankar View Post
25MPH is just 40KPH i'm sure that 40kph is possible in city roads, atleast here its possible. Many small aero mods combined together would yield benefits. Each on their own would add their tiny bit to help, when combined the difference would be measurable.

Smooth wheel cover, flat underbody, properly filled tyres, critically placed VGs, front air dams, lowered stance etc.. Not all of these are possible on Indian roads.
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