Model 3 headlamps may be vortex generators

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JeffC

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#1
@Ryan noticed that his headlamps were not flush with the body:

https://teslaownersonline.com/threads/performance-model-3-vins.7702/page-13#post-132209

Regarding the headlights sticking up into the wind a couple millimeters, after seeing that on multiple Model 3s, I'm starting to think it could be by design as an aerodynamic aid, sort of like the pointy headlamps on Leafs. If so, this could be what's called a "vortex generator" to help direct and shape the airflow over the front of the car. That's the function on the Leaf, for example.

https://en.wikipedia.org/wiki/Vortex_generator

Also, the inside edge of the Model 3 headlamp looks somewhat like half of a reversed NACA duct oriented along the local airflow. NACA duct shapes work by generating a vortex. The purpose of a vortex generator at the headlight position may be to direct the airflow over the hood and over the fender towards the side of the car and to keep the airflow attached better at the side of the car.

https://en.wikipedia.org/wiki/NACA_duct



The crease on the rear fender of Model 3 (and to a lesser extent Model S) may also be a vortex generator to help keep the airflow attached better at the back of the car.

(Every longitudinal crease on Model 3 (and many other well designed cars) is probably a vortex generator and is likely there for highly specific aerodynamic purposes. And they also integrate into the overall airflow around the car.)


From the front of the car, you can see the reversed half NACA duct shape of the inside edge of the headlight. It's wide in front and has a distinct shoulder which leads into the narrow part. So does half of a NACA duct. (This is particularly clear on the right side of the car due to the camera angle.) The shape is angled to the local airflow, which is somewhat diagonal at that place in the front of a car. The airflow is not straight back but bends to the sides a bit. So the reversed NACA duct shape is also angled towards the side of the car. The airflow is not straight back, so the vortex generator is not oriented straight back either. It's oriented to the air flow.

(Compare the shape in the orange-red circles below, to half of the NACA ducts (split lengthwise) in the picture above. They look similar to me, after taking into account the diagonal skew of the airflow that is likely slightly towards the side of the car and not straight back.)



I've taken some pictures of the headlamps on multiple Model 3s, particularly looking from the back down through the likely airflow. You can see they all stick up about 2mm. I propose that's by design to act as a vortex generator and influence the airflow along the sides of the car.


(It's a bit hard to see above, but the headlamps stick up into the wind by a couple mm above the bodywork. I tried to pick a camera angle that shows that difference, and also the path the airflow might take over it.)

Vortex generators work by tripping and folding the airflow, causing vortices that usually trail in the airflow behind the generator. They do create a little drag, but also add energy to the local airflow that is often used to help keep airflow attached longer to the surfaces behind them in the airflow. Placed at the front of the car, if the headlamps are vortex generators it would seem to mostly affect the airflow over the fender, under the side mirror and along the side of the car, again to keep airflow better attached there.

The net effect should be better overall airflow, and ironically lower overall drag.

On airplane wings, vortex generators are sometimes used to keep airflow attached longer, particularly at higher angles of attack, for example during takeoffs and landings. You can see those as little metal tabs on the tops of some wings:

 
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Mesprit87

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#2
I'm not with you on this, if Tesla had some kind of trick with their headlights they would have said so when everybody was bashing them about poor fit.

As for the vortex generators, having a background in flight test, they are usually cheap last resort solutions for a bad design. I sure don't want them on my car.

Interesting theory though;)
 

JeffC

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#3
I'm not with you on this, if Tesla had some kind of trick with their headlights they would have said so when everybody was bashing them about poor fit.

As for the vortex generators, having a background in flight test, they are usually cheap last resort solutions for a bad design. I sure don't want them on my car.

Interesting theory though;)
Agree with your thoughts, but I'm sure Tesla doesn't want to reveal all of their secrets, and the shape of the headlamps sure does look like half of a NACA duct, reversed, to me. That could fit the theory of them being very mild vortex generators.

Also I haven't spotted a Model 3 where the rear part of the headlight doesn't stick up into the wind a couple mm. Tesla has some very minor quality problems, but this looks like it could be deliberate design. My closeup pictures above have the back of the light sticking up and the front edge nearly flush with the bodywork. That's reminiscent of how a normally-oriented NACA duct opening tapers down from the bodywork at the front. I.e., the transition into the vortex generating vertical surfaces of the NACA duct is gradual.

While vortex generators are considered somewhat kludgey, even some of the best wing designs seem to have them. Every Boeing and Airbus airliner I've been on has had a few near the maximum camber (a little aft of the tallest part of the wing). I hope the wing designers who put them there don't consider them to be failed designs. :) On small planes they may be more kludgey. Sometimes they do seem beneficial on aircraft, and maybe more often than engineers would like to admit.

(I was going to include some Airbus and Boeing wing pictures, but didn't find some handy on wikipedia.)
 
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Quicksilver

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#4
I am thinking it is a manufacturing tolerance issue rather than aerodynamics. It would be interesting to hear from Franz on the design of those head lamps.
 

Mesprit87

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#5
Every Boeing and Airbus airliner I've been on has had a few near the maximum camber (a little aft of the tallest part of the wing). I hope the wing designers who put them there don't consider them to be failed designs
The fact that it is widely used doesn't mean it's good.
Correct me if I'm wrong but we don't see these in recent designs from big manufacturers (the A350 doesn't for sure). From my experience on Bombardier products (and they have a reputation for designing slipery wings), they haven't used these in decades other than vintage learjets. We sure didn't need any on the Cseries aka A220.
As for the naca theory, they are used when air needs to be channeled in an orifice that wouldn't get any pressure otherwise because of the boundary layer.

I still vote for a $$$$$ case of having the supplier change the contour or getting rid of the batch already made, who knowso_O
 
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JeffC

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#6
The fact that it is widely used doesn't mean it's good.
Correct me if I'm wrong but we don't see these in recent designs from big manufacturers (the A350 doesn't for sure). From my experience on Bombardier products (and they have a reputation for designing slipery wings), they haven't used these in decades other than vintage learjets. We sure didn't need any on the Cseries aka A220.
As for the naca theory, they are used when air needs to be channeled in an orifice that wouldn't get any pressure otherwise because of the boundary layer.

I still vote for a $$$$$ case of having the supplier change the contour or getting rid of the batch already made, who knowso_O
IMO the fundamental reason NACA ducts work is that their shape generates vortices where the wall perpendicular to the surrounding surface is, and that's how they're more efficiently able to direct airflow into their intake. The vortices help keep the airflow attached as it moves down the ramp into the "mouth" of the duct. If so then using a similar shape as a generalized vortex generator seems possible.

The F-18 leading–edge root extensions similarly generate vortices that probably help the air stay attached on the top of the wing, allowing higher angles of attack. The resulting planform shape of the wing is a blended delta, not unlike the general shape of a NACA duct.

I have definitely seen vortex generators on common airliners such as current production 737, etc.

 
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I have definitely seen vortex generators on common airliners such as current production 737, etc.
I don’t think so...

I did not take any aerodynamics, fluid dynamics, or for that matter any sort of dynamics classes. However, I m a y have taken some manufacturing dynamics :nomouth::screamcat: :tearsofjoy: which have might have led to a short stint in pacemaker manufacturing in a previous life. Those fixed tabs on the low-pressure side of the wing appear to me to help stabilize the disturbed air flow during take-off and landing when the take-off/landing tabs are set to increase lift at slower speeds. I don’t believe they are vortex generator as you have suggested. Hopefully, an aviation person will come along to edumacate ;) this Curious George.
 

Mesprit87

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CoastalCruiser

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#10
According to page 37 of the Model 3 Emergency Response Guide, they are NOT Vortex Generators, but rather unlicensed nuclear accelerators. It sates the ducts are there to prevent the beams from crossing in case of collision.
 

JeffC

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#11
I don’t think so...

I did not take any aerodynamics, fluid dynamics, or for that matter any sort of dynamics classes. However, I m a y have taken some manufacturing dynamics :nomouth::screamcat: :tearsofjoy: which have might have led to a short stint in pacemaker manufacturing in a previous life. Those fixed tabs on the low-pressure side of the wing appear to me to help stabilize the disturbed air flow during take-off and landing when the take-off/landing tabs are set to increase lift at slower speeds. I don’t believe they are vortex generator as you have suggested. Hopefully, an aviation person will come along to edumacate ;) this Curious George.
The short, ~15 mm tall, tabs on the top of the wing just aft of the maximum camber (behind the tallest part of the wing) are vortex generators. They stabilize the airflow on the top of the wing by inducing vortices that energize the boundary layer and help keep it attached longer at relatively high angles of attack, as encountered during takeoffs and landings.
 
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JeffC

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#12
"The 737 was originally envisioned in 1964. The initial 737-100 made its first flight in April 1967"
https://en.m.wikipedia.org/wiki/Boeing_737
Not my idea of a fresh design, once manufacturer certify something they leave it alone as much as possible.

Hey, you're right, I think I found the vortex generator in the model 3;)
https://www.sciencedirect.com/science/article/pii/S0017931017352304

Fresh clean wing:)
View attachment 12698 View attachment 12699
Apparently both Airbus and Bombardier (which are the images you showed) shun vortex generators. Boeing does not (though they use them more sparingly in recent designs).

787:


737-900:


They don't seem to hurt eithers' energy efficiency.
 
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mkg3

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#14
VGs are bandaid solution to fixed design. When 757 was designed, it was pre-CFD (computational fluid dynamics) days and the only method used was good 'ol fashion wind tunnel models and engineering know-how. As it turned out, it was terrible and flow separated easily at the slight incidence angle, much less angle of attack. Boeing added VG's all along the wing to keep the flow attached - at the expense of increasing drag. But the drag induced was significantly less than the drag due to flow separation, not to mention loss of lift too.

Today, most aircraft are designed using CFD and WT as a simulation validation such that VGs are used only as one of the last resort. Clean wing is ALWAYS better than those with much of stuff added.

As for T3's headlamps serving some aerodynamic function, other than the part of front facia and the overall airflow around the font of the vehicle, it is not. Just look at the profile view of the vehicle and you'll see that the headlamp position is located such that its prior to where a max camber would occur on the fender line. In other words, VGs will only mess up the flow aft of the headlamp and would interfere with the hood lines that direct airflow to and between the front windows and the mirrors, hence increasing the overall drag.
 

JeffC

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VGs are bandaid solution to fixed design. When 757 was designed, it was pre-CFD (computational fluid dynamics) days and the only method used was good 'ol fashion wind tunnel models and engineering know-how. As it turned out, it was terrible and flow separated easily at the slight incidence angle, much less angle of attack. Boeing added VG's all along the wing to keep the flow attached - at the expense of increasing drag. But the drag induced was significantly less than the drag due to flow separation, not to mention loss of lift too.

Today, most aircraft are designed using CFD and WT as a simulation validation such that VGs are used only as one of the last resort. Clean wing is ALWAYS better than those with much of stuff added.

As for T3's headlamps serving some aerodynamic function, other than the part of front facia and the overall airflow around the font of the vehicle, it is not. Just look at the profile view of the vehicle and you'll see that the headlamp position is located such that its prior to where a max camber would occur on the fender line. In other words, VGs will only mess up the flow aft of the headlamp and would interfere with the hood lines that direct airflow to and between the front windows and the mirrors, hence increasing the overall drag.
Yes, vortex generators are often thought of as a band aid. But in the real world, they can be useful.

737-900 and 787 wings were designed with CFD and still have some vortex generators (pictures above).

The Model 3 headlamps are definitely in a high pressure area. They could have an effect downstream, along with the other longitudinal creases. The vortex generators on the Cesna wing that I linked above are well before maximum camber. Like the Tesla headlight, they're near the leading edge of the wing.

When I get my Model 3, if it's headlights' back ends also stick out into the wind, I'll get a fan and some smoke and see if I can photograph vortices off them. (If they don't stick out, then it's poor manufacturing quaility. ;P ) Of course my fan may not have laminar flow anywhere.
 
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JeffC

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#17
I don’t even care who’s wrong or right here dammit!! I’m telling everyone from here on my car generates vortices!!!

:cool:< vortices, man
It definitely generates vortices, most of them probably highly intentional. However other cars also do that. Any creases, folds, etc., large enough in bodywork and exposed to airflow can generate vortices. Really any tall enough discontinuity can.
 
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TheTony

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#18
Just to be clear, what Ryan described was on the bottom side of the headlamp, not the top. I read the OP's explanation of how 'sticking up into the wind' would affect/benefit airflow. However, this ignores the fact that these headlamps are flush on the top edge. It's the bottom edge that is not sitting flush with the front bumper.

Quite a few people have reported this (my 3 displays it also). It was initially unclear if this was by design or a minor defect in assembly. A number of people who have noticed it have contacted SCs - some were told it was "within spec" but others have had it adjusted to sit flush - it was logged in the paperwork as a bumper fitment issue.

Here is a recent thread about this very issue, complete with reports from other owners, photos of the issue (before and after) and a snapshot of the work order from someone who has had it adjusted by their SC.
 

JeffC

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Just to be clear, what Ryan described was on the bottom side of the headlamp, not the top. I read the OP's explanation of how 'sticking up into the wind' would affect/benefit airflow. However, this ignores the fact that these headlamps are flush on the top edge. It's the bottom edge that is not sitting flush with the front bumper.

Quite a few people have reported this (my 3 displays it also). It was initially unclear if this was by design or a minor defect in assembly. A number of people who have noticed it have contacted SCs - some were told it was "within spec" but others have had it adjusted to sit flush - it was logged in the paperwork as a bumper fitment issue.

Here is a recent thread about this very issue, complete with reports from other owners, photos of the issue (before and after) and a snapshot of the work order from someone who has had it adjusted by their SC.
For info, I'm mostly referring to the inside, generally longitudinal edge of the headlamp, not the bottom edge. The top edge tapers to a wedge that mostly lines up with a fender crease. (That longitudinal fender crease also almost certainly acts as a vortex generator, intentionally.)
 

TheTony

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For info, I'm mostly referring to the inside, generally longitudinal edge of the headlamp, not the bottom edge. The top edge tapers to a wedge that mostly lines up with a fender crease. (That longitudinal fender crease also almost certainly acts as a vortex generator, intentionally.)
I'm aware of what you're pointing out. However, you did so in the context of what Ryan pointed out. His issue was on the bottom edge. He specifically noted the bottom of the headlamp assembly was where it was not flush with the adjacent panel.

I actually haven't heard of any Model 3s where the headlight was not sitting flush on any side of the headlamp except for the bottom edge. If you have links to folks who have ones with the leading edge not flush, I'd be curious to see it. Essentially, the issue with the bottom of the headlamp assembly is that it overlaps the top of the front bumper surface directly below it by a fraction of an inch. One user in the thread I linked to called it an "overbite".

So, I'm not really aiming to engage on the idea of "vortex generators" on the 3, more to the fact that the surface you're suggesting isn't flush is not the one in question for most (all?) of the people who are reporting headlight fitment issues. In reality, I believe many people have this issue (bottom edge) and haven't even noticed it. I certainly didn't notice it right away, as it is the same on both headlamps, so it looks symmetrical and as if it could be intentional.