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I added some VG's.. ofcourse there are pics


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Welp.. I have been wanting to install my vortex generators for sometime now.. I bought them for $19.99 from a company by the name of Vortekz Generators.

 

There are supposed to be installed at various angles.. the inner 4 are 15* degrees from the roof line.. the next outer VG is 10* degrees, then the 2nd to the last are 5* degrees then the final outside VG's are parallel with the roof line

 

 

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OK OK i realize in the very last picture they are not PERFECT.. but it's hard to do i'm telling ya! But it still does its job.

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Wait a sec...

 

I was looking at SDI's VG's...

 

100_2485.jpg

 

Seems mine look backwards..

 

BUT I followed the directions from Vortekz..

 

oncarblutest.jpg

recdegrees.jpg

 

and this was tested effective in the windtunnel

 

PICT0563.jpg

PanteraHatch.jpg

 

Which is right?!

 

 

 

http://www.mitsubishi-motors.com/corporate/about_us/technology/review/e/pdf/2004/16E_03.pdf

 

I was reading Mitsubishi's article.. and they seem to be at ZERO degrees.. hmm

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From the Mitsu article, page 13:

The delta-wing-shaped VGs should be installed at a

yaw angle of 15° to the airflow direction. In order to

meet this condition, the direction of airflow at the roof

end was investigated by oil flow measurement. Airflow

direction was found to be different between sideways

positions on the roof. The airflow is aligned directly

with the backward direction at center of a car, but it

increasingly deviates toward the center as the measurement

point shifts away from the central position. For

this reason, the delta-wing-shaped VGs must be

installed at an angle of 15° against the vehicle centerline

for the central position, whereas they must be

installed at an angle near 0° for outermost positions.

 

This tells me you did it right, and I have a hunch there wouldn't be much of a vortex created if you had them straight in line all the way across. This kinda makes sense too if you read what they said. In the center the airflow is straight back, so you angle the VG. On the ends, the airflow is directed more towards the center of the car so the VG is installed straight and that puts it at an angle to the airflow.

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OK..

 

I called a company by the name of MicroAero who produces vortex generators for Cessna, Beechcraft, Piper etc.. and I spoke to a wonderful technical ops manager.

 

He said that mounting the VG's parallel with the wind is NOT effective...

 

They mount the VG's pigeon toe'd on the leading edge of the wings which can be as high as 30* degrees.. He said there should be no difference in which direction the VG's are mounted (pigeon or duck (opposite)).

 

Here are some pics to support the data

 

CA185FVGInstall.jpg

CP210Tail.jpg

CA185F.jpg

CP210.jpg

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What I'm getting out of this is that Mayolives's VG's are probably not as effective as yours, because in the Mitsubishi example the airflow tended towards the center, and he's got his VG's angled toward the center. The difference I think is that an airplane wing is mostly out by itself cutting through the air, while in comparison the roof of the car is not the only consideration, you've got a bunch more crap in the airflow to deal with.

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also if you notice that on the airplane stuff that the vortex generators are mounted on either the leading edge or on the outermost point on teh airfoil. I think if the VGs were mounted on the center of the Z's roof it would be more effective by cutting into open wind rather than wind that is flowing DOWN the back of the car already.

Maybe VGs mounted right at the rear of Ryan's moon roof would be cutting into clean air a little more.

 

It just seems odd that the airplane guys are mounting these where they can be seen from a straight-on view and we are mounting them rearward on the roof where they can't really be seen from straight on.

 

 

Just my 2 cents on the aero subject...

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PrOxLaMuS© You are really working hard there man! It looks good! You are taking this aero stuff to heart. It seems that many here that chipped for the testing are taking cues from the data aquired! That is the best part! We all came together, and are actually doing something with this knowledge. The spirit of hot rodding!

 

Keep up the effort. DO!, while some others talk about doing!

 

Scott

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also if you notice that on the airplane stuff that the vortex generators are mounted on either the leading edge or on the outermost point on teh airfoil. I think if the VGs were mounted on the center of the Z's roof it would be more effective by cutting into open wind rather than wind that is flowing DOWN the back of the car already.

Maybe VGs mounted right at the rear of Ryan's moon roof would be cutting into clean air a little more.

 

It just seems odd that the airplane guys are mounting these where they can be seen from a straight-on view and we are mounting them rearward on the roof where they can't really be seen from straight on.

The thing that I got from researching this is that the wing changes its angle of attack, where the car really doesn't change more than a couple of degrees. So you put the vortex generators in a position where they're right at the point on the car where the flow starts to separate, and they cause the vortices and essentially stick the airflow to the shape of the car again. On the wing that is going to be quite a bit farther forward than the car. I'm not saying that there might not be a better vortex created by putting the VG's in clean air, but I think the trade off might be a lot more drag. Possibly something to check out in the next round of wind tunnel tests...

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thanks guys!

 

The way the VG's are mounted on the wings are exactly as Jon mentioned..

 

The VG's really take effect at HIGH angles of attack.. (ie right before the wing stalls)

The aircraft stalls because the aircraft exceeds the angle of attack and the airflow no longer accelerates over the leading edge of the wing and buffets behind the wing.

 

If you notice the way the VG's are mounted on the Cessna's, at the highest angle of attack to maintain slow flight (55kts) the VG's are just below the highest point of the leading edge.. allowing the VG's to take effect and keep the air flowing and accelerating down the wing.

 

Now in a Z car.. the air flowing over the top of the car actually accelerates down the rear hatch before it seperates from the boundary layer. The point of the VG's is to increase the boundary layer seperation and keep the air accelerating down the hatch, which increases the effectiveness of the spoiler!

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Prox,

 

I have those same VG's...I was wondering if I made a bad buying decision after I ordered those since the VG "rudders" for the WRX STI are more pyramid in shape rather than the constant width cross-sectional profile (going straight up without any taper).

 

I ordered a set for my S130 as well. Maybe I can be the first one on the "Hybrid-z block" mount those, lol. If I remember right, they are supposed to be mouned 3-4" ahead of where the flow seperates along the rear hatch. Where did I see the the pic of the streamlines going over the clay model of the S130? I just want a good idea of how far forward to mount them from the hatch...there isn't much playroom between the t-tops and the part of the roof that transitions to the hatch (only on coupes).

 

Eh...I'll post some pics to better illustrate what the heck I'm talking about.

 

You guys are way ahead of me...I have some catching up to do!!

 

Cheers, -Hugh

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Hughdogz: the S130 already has a "bump" right above the hatch, supposedly put there by the Nissan engineers to seperate the boundary layer from the rear hatch, thereby reducing lift (TonyD and I butted heads about this awhile back). Which brings me to a larger question:

Isn't it the purpose of vortex generators to enhance boundary layer adhesion? Isn't this why they are useful on wings, because they enhance lift? Isn't that what we're trying avoid with our cars? I can understand the concept of trying to get air to the rear spoiler to enhance it's downforce properties, but it seems contradictory to increase lift in one spot, just to try and decrease it with a spoiler/wing 3 feet later. Please somebody, send me to school on this...

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Hughdogz: the S130 already has a "bump" right above the hatch, supposedly put there by the Nissan engineers to seperate the boundary layer from the rear hatch, thereby reducing lift (TonyD and I butted heads about this awhile back). Which brings me to a larger question:

Isn't it the purpose of vortex generators to enhance boundary layer adhesion? Isn't this why they are useful on wings, because they enhance lift? Isn't that what we're trying avoid with our cars? I can understand the concept of trying to get air to the rear spoiler to enhance it's downforce properties, but it seems contradictory to increase lift in one spot, just to try and decrease it with a spoiler/wing 3 feet later. Please somebody, send me to school on this...

This has already been gone over in some detail in this other thread: http://forums.hybridz.org/showthread.php?t=115294

 

But the short answer is that you are wrong, and this is why: The vortex generators are there on an airplane to energize the boudary layer so that the airflow over the FLAPS has some effect. It's the effectiveness of the FLAPS that increases the effectiveness of the control surfaces when the wing approaches stall. In the case of the car, when the flow separates there is a vacuum in the area where the flow has separated. This is less pressure on the hatch than what you have with non separated "low pressure" vortices traveling over it. So even without a spoiler, non-separated flow will give you more downforce than separated flow will. But the big benefit is when there is a spoiler or a wing involved the airflow to that "control surface" is energized, which makes it more effective in producing downforce.

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This has already been gone over in some detail in this other thread: http://forums.hybridz.org/showthread.php?t=115294

 

But the short answer is that you are wrong, and this is why: The vortex generators are there on an airplane to energize the boudary layer so that the airflow over the FLAPS has some effect. It's the effectiveness of the FLAPS that increases the effectiveness of the control surfaces when the wing approaches stall. In the case of the car, when the flow separates there is a vacuum in the area where the flow has separated. This is less pressure on the hatch than what you have with non separated "low pressure" vortices traveling over it. So even without a spoiler, non-separated flow will give you more downforce than separated flow will. But the big benefit is when there is a spoiler or a wing involved the airflow to that "control surface" is energized, which makes it more effective in producing downforce.

 

 

Thanks,Jon. That explanation works for me!

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Hughdogz: the S130 already has a "bump" right above the hatch, supposedly put there by the Nissan engineers to seperate the boundary layer from the rear hatch, thereby reducing lift (TonyD and I butted heads about this awhile back).

 

Innnnnteresting...I wonder if the VG's would keep the turbulent flow from "seperating" more or would it hurt performance?

 

Also, when I stuck those VG's on my S30 last night, I think I have them set too far forward. Damn, I should have studied those wind tunnel and the pics Prox posted better. I have the rear of them set about four inches from the rear glass, not two. I didn't want to remove them and set them back more from fear of pulling my paint off and having un-usable double sided adhesive...I suppose I'll wait until a hot summer day and see if I can coax them off and re-locate them.:cry2:

 

Later, -Hugh

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Innnnnteresting...I wonder if the VG's would keep the turbulent flow from "seperating" more or would it hurt performance?-Hugh

 

Well, since my understanding of VG's has improved since I posted this morning, I would say yes. VG's should work to keep the air attached farther down the hatch. If you have an aerodynamic device (spoiler/wing) at the end of your hatch, more air goes over it, thereby increasing it's effectiveness.

 

So why does the S130 have that "bump" above it's hatch? Were the designers addressing the exhaust fume issue of the S30? Is that all is needed to help the S30? These are my questions, especially since, personally, I'd rather NOT put a rear spoiler on my tail, but I'm not against something around the upper hatch area.

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